Asian Citrus Psyllid

Control Program in the 

Continental 

United States and 

Puerto Rico

Environmental Assessment

August 2010

United States 

Department of 

Agriculture

Marketing and 

Regulatory 

Programs

Animal and 

Plant Health 

Inspection 

Service
Asian Citrus Psyllid 

Control Program in the 

Continental United States and 

Puerto Rico

Environmental Assessment

August 2010

Agency Contact:

Osama El-Lissy

Director, Emergency Management

Emergency and Domestic Programs

Animal Plant Health Inspection Service

U.S. Department of Agriculture

4700 River Rd. Unit 134

Riverdale, MD 20737

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Table of Contents

 

I. Introduction ................................................................................... 1

A. Asian Citrus Psyllids...............................................................1

B. Citrus Greening .......................................................................2

C. Range of ACP and CG in the United States ...........................4

D. Current ACP and CG Management Actions...........................5

E. Previous Environmental Documentation.............................10

II. Purpose and Need........................................................................11

 III. Affected Environment ..................................................................13

IV. Alternatives...................................................................................13

A. No Action............................................................................... 13

B. Cooperative Federal, State, and Industry ACP and CG 

Management Program ...........................................................14

1. Strategy .............................................................................14

2. Surveys .............................................................................15

3. Diagnostics .......................................................................15

4. Public Education and Outreach.......................................15

5. Chemical Treatment for ACP ...........................................16

6. Biological Control of ACP................................................18

7. Quarantine.........................................................................18

 

V. Environmental Consequences.....................................................18

A. No Action ................................................................................18

B. Cooperative Federal, State, and Industry ACP and CG 

Management Program............................................................19

1. Survey, Identification and Diagnostics, Public 

Education and Outreach, and Strategy ...........................19

2. Chemical Treatments for ACP Control............................20

3. Biological Control.............................................................62

4. Quarantine.........................................................................62

C. Cumulative Effects.................................................................62

VI. Other Environmental Considerations..........................................65

A. Endangered Species..............................................................65

B. Executive Orders....................................................................65

C. National Historic Preservation Act of 1966 ..........................67

VII. Listing of Agencies and Persons Consulted...............................68

VIII. References ....................................................................................69

Appendix A. ACP and CG (Ca. L. asiaticus) Host Plants 

Appendix B. Positive ACP Counties and Temperature Suitability 

Map

Appendix C. U.S. Counties with Commercial Citrus Production

Appendix D. Affected Environment for the Proposed ACP 

Control Program
1

I. Introduction

Asian citrus psyllids (ACP), Diaphorina citri Kuwayama, were first found 

in the United States in 1998. The psyllids are known to transmit a 

bacterium named Candidatus Liberibacter asiaticus (Ca. L. asiaticus). 

Although not harmful to humans and animals, Ca. L. asiaticus causes 

Huanglongbing (HLB), or citrus greening (CG) in citrus and its close 

relatives (e.g., limeberry and trifoliate orange). 

CG has resulted in extensive economic losses to the citrus production 

worldwide (NAS, 2010; Gottwald and Graham, 2008; and Norberg, 2008). 

Infected citrus orchards are usually destroyed or become unproductive in 

5 to 8 years (Bové, 2006). In order to prevent the introduction and spread 

of CG into other citrus-growing areas, the U.S. Department of Agriculture 

(USDA), Animal and Plant Health Inspection Service (APHIS) has 

determined the need to control ACP. This environmental assessment (EA) 

will analyze the potential environmental impact of the proposed ACP 

control program.

A. Asian Citrus Psyllids

ACPs are small insects, 3 to 4 millimeters (1/8 to 1/6 inch) in length with 

brown mottled bodies and light brown heads. Their bodies are covered 

with a whitish, waxy secretion that makes them appear dusty (see 

figure 1). Adults may live for several months. Psyllids are most active 

when a plant has new growth. Adult psyllids commonly aggregate on 

young, tender plant tissue where they feed and mate. 

 

Fig. 1. Adult Asian citrus psyllid on a young

citrus leaf. (Photo credit 

USDA–ARS–National Invasive Species 

Information Center, D. Hall. 

http://www.invasivespeciesinfo.gov/animals/acp_child.shtml)

After mating, female psyllids feed on flush (new, tender terminal 

branches) to produce mature eggs. Females may produce up to a 

maximum of 520 to 1,900 eggs (Husain and Nath, 1926; Pande, 1971; Liu 
2

and Tsai, 2000; Tsai and Liu, 2000). Eggs are inserted into the leaf tissue 

inside the folds of unexpanded leaves, on the edges of young leaves, or at 

the base of leaf buds. There can be as many as 9 to 10 generations of 

psyllids a year. The immature stage of the psyllid, or nymph, is found on 

new growth and move in a slow, steady manner when disturbed. The 

adults leap when disturbed and may fly a short distance (Mead, 1977). 

Even without transmitting Ca. L. asiaticus, ACP can cause damage to host 

plants (see appendix A for a list of host plants). While feeding on plant 

fluids, toxins present in the ACPs’ saliva are injected into the plant. The 

toxins cause curling and distortion of young leaves; however, this damage 

is minimal compared to the damage caused by transmitting Ca. L. 

asiaticus. ACP can acquire Ca. L. asiaticus while feeding on host plants 

infected with the bacterium. After a latent period,

1 the psyllid is able to 

transmit the pathogen to other host plants. Transmission of the pathogen 

is thought to occur through salivary secretions. ACP can carry and 

transmit Ca. L. asiaticus to host plants throughout its entire life. ACP can 

also transmit Ca. L. asiaticus to its offspring. 

B. Citrus Greening

CG is considered to be one of the most serious citrus diseases in the world. 

The disease has been found in Africa, Asia, Mexico, the Caribbean, 

Central America, South America, North America, and the Saudi Arabian 

Peninsula. CG attacks the vascular system of host plants. The pathogen is 

phloem-limited, inhibiting the food-conducting tissues of the host plant, 

and causes yellow shoots, asymmetrical chlorosis2 (referred to as blotchy 

mottle) (see figure 2), reduced foliage, small misshaped (see figure 3), 

bitter tasting fruit, fruit that remains green at one end after maturity (see 

figure 4) and tip dieback in citrus plants and their close relatives.

Fig. 2. Sweet orange tree exhibiting blotchy

mottle. (Photo credit Hilda Gomez, USDA)

 1 An interval of time between exposure to the infection and subsequent consequences of infection.

2 Abnormal yellowing (or whitening) of green leaves.
3

Fig. 3. Misshaped mandarin fruit infected 

with CG disease. (Photo credit J.M. Bové, 

INRA Centre de Recherches de Bordeauz, 

National Invasive Species Information Center. 

http://www.invasive.org/species/subject.cfm?sub=4695.)

Fig. 4. Mature tangelo fruit infected with CG

disease. (Photo credit Hung Shih-Cheng, 

Taiwan Agricultural Research Institute) 

Ca. L. asiaticus, the pathogen that causes CG, is transmitted by two 

vectors, ACP and the African citrus psyllid (Trioza erytreae (del 

Guercio)). The African citrus psyllid is not known to be present in the 

United States. Ca. L. asiaticus can also be transmitted by grafting and, 

under laboratory conditions, by dodder.3 

Once infected, there is no cure for a tree with CG. In areas of the world 

where CG occurs, citrus trees decline and die within a few years and may 

never produce usable fruit. CG greatly reduces production, destroys the 

economic value of the fruit and juice, and can kill trees. While ACP can 

cause economic damage to citrus groves and nurseries by direct feeding, 

APHIS considers this damage to be minimal compared to the damage and 

subsequent economic impacts caused by CG. 

The severity of the disease in Asia has been well substantiated in 

literature. In 1966, Fraser et al. stated that the catastrophic losses of citrus 

trees in India were likely due to CG (as cited by da Graça, 1991). In the 

 3 A parasitic plant of the morning glory family that lacks leaves, roots, and chlorophyll, but have 

special suckers for drawing nourishment from its host.
4

Philippines, a significant loss in the area of land planted with citrus from 

1961 to 1974 was primarily attributed to leaf mottling or CG (Altamirano 

et al., 1976). The Food & Fertilizer Technology Center for the Asian and 

Pacific Regions indicate that as a result of infection by CG, average citrus 

yields in Asia have been falling. For example, the average citrus yield in 

Vietnam’s Nghe An Province during the 1960s was 18 to 20 million tons 

per hectare (mt/ha) (2.47 acres). In 2003, average yields were reduced to 

around 6 to 9 mt/ha. The life span of citrus groves fell from 17 to 18 years 

in the 1960s to less than one third of that in 2003 (FFTC, 2003). 

Economic losses are directly related to the life span of the citrus trees. 

The longer the trees live, the greater the return to farmers. For example, if 

a citrus grove in Thailand lives for only 6 years, a farmer would suffer a 

loss of $8,292 per ha (2.47 acres) of citrus. If a grove lives for 8 years, a 

farmer would suffer a loss of $3,660 per ha. Only if a grove survives for 

10 years will there be a profit of $3,383 per ha (Roistacher, 1996). 

C. Range of ACP and CG in the United States

ACP was first discovered in the United States in Palm Beach County, 

Florida, in 1998. Subsequently, CG was detected in Miami-Dade County, 

Florida, in 2005. Currently, ACP is present in Alabama, Florida, Georgia, 

Hawaii, Louisiana, Mississippi, Texas, Guam, Puerto Rico, U.S. Virgin 

Islands, and portions of Arizona, California, and South Carolina. CG is 

currently known to be present in Florida, Georgia, Puerto Rico, U.S. 

Virgin Islands, and portions of Louisiana and South Carolina. 

ACP is restricted by the range of its host and is more prevalent in the 

United States in hot coastal areas (Sullivan and Zink, 2007). Under 

laboratory conditions, the optimal range of temperatures for population 

growth in growth chambers is 77 to 82 °F (Liu and Tsai, 2000). Adults 

can live for 1 to 2 months at temperatures below 68 °F (Sullivan and Zink, 

2007). (See appendix B for a map of U.S. counties where there has been a 

positive detection of ACP, as well as areas that are suitable for ACP 

establishment based upon cold temperature mortality.) There is little 

information available on whether rainfall or irrigation influences vector 

survival or establishment (Sullivan and Zink, 2007). It is known that ACP 

populations reach high levels in arid regions of the world where citrus is 

produced, including Saudi Arabia (Bové and Garnier, 1984), Yemen 

(Bové and Garnier, 1984), and Iran (Bové et al., 2000). 

Ca. L. asiaticus is well adapted for temperatures occurring across the 

citrus belt of the United States (Sullivan and Zink, 2007). The traditional 

citrus climate extends from northern California through southern 

California and into the low Arizona desert. There is a break in New 

Mexico because of the State’s high elevation and cold winters, thus 

causing an absence of host plants. The citrus belt picks up again in 

southern Texas and extends along the Gulf Coast and into Florida 
5

(Sullivan and Zink, 2007). As previously mentioned, CG is known to be 

present in Florida, Georgia, Louisiana, Puerto Rico, U.S. Virgin Islands, 

and as far north as Charleston, South Carolina. Symptoms of CG are

influenced by the temperatures at which affected trees grow (Bové, 2006).

D. Current ACP and CG Management Actions

The goal of ACP management programs is to reduce the level of 

populations. By reducing the number of ACPs populating an area, it is 

generally accepted that the chance of Ca. L. asiaticus being introduced or 

spread throughout an area is lowered. However, due to the number of 

psyllids present and their ability to disperse, management programs have 

never completely eliminated ACP from an area. Because the vector 

(ACP) can never be fully eradicated, the control of CG is dependent upon 

areas infected with CG being quickly identified and eliminating any host 

plants infected with CG. However, the elimination of CG from an area 

has also never been successful (Rogers et al., 2009a). This is due partly to 

the fact that trees can be infected and contagious with CG yet not show 

symptoms for several years. In addition, there are currently no 

antimicrobials effective against Ca. L. asiaticus. 

A pest management program for ACP could include chemical and 

biological control measures. In areas of the world where citrus is grown 

and CG is present, the use of insecticides to control ACP has been a major 

component of CG management strategy (Rogers et al., 2009a). No 

scientific data has been collected in the countries where insecticides were 

used against ACP to demonstrate that insecticides slowed the spread of 

CG; however, “...anecdotal evidence suggests that reducing psyllid 

populations via insecticide application does help to slow the rate of spread 

of the disease” (Rogers et al., 2009a). Management programs should,

whenever possible, optimize an affordable ACP control program (e.g., 

reduce the number of pesticide applications used) while minimizing

negative impacts on important natural predators (Stansly et al., 2008). 

However, any reductions in pesticide usage must be tempered by the need 

to achieve a high rate of control of ACP, which, in turn, are expected to 

result in effective control of CG.

In addition to insecticides, some areas are using biological control agents4

 4 Biological control agents are organisms that are natural predators, parasites, or pathogens of a pest 

that work to decrease a pest’s populations to a more desirable level.

to decrease ACP populations and control CG. CG and its two vectors, 

ACP and African citrus psyllid, have threatened citrus crops of Reunion, 

an island located in the Indian Ocean east of Madagascar. A control 

strategy implemented in the mid-1970s consisted of setting up disease-free 

nurseries using healthy trees and promoting the biological control of both 

psyllids by importing exotic natural enemies. The approach was effective 
6

in reestablishing profitable domestic citrus production within this tropical 

island ecosystem (Aubert et al., 1996). There are also predators of ACP 

naturally present which may assist in controlling ACP populations, such as 

lacewings and ladybeetles. In addition to reducing ACP populations, the 

use of insecticides has reduced populations of natural predators of ACP 

(Qureshi and Stansly, 2007).

Routine scouting for infected trees is necessary to control for CG 

(Brlansky et al., 2010). Leaves with yellowing veins and blotchy mottle 

are the most diagnostic symptom of the disease; however, nonspecific 

foliar symptoms are sometimes difficult to distinguish from nutritional 

deficiencies and other plant diseases (Irey et al., 2006a and 2006b). There 

are laboratory tests that can be done if confirmation of the disease is 

necessary (Irey et al., 2006; Li et al., 2006). Any infected trees should be 

removed from the area and destroyed. Prior to removing the tree, the tree 

should be treated with a foliar insecticide. The foliar insecticide should

kill any adult psyllids that would have dispersed from the tree during 

removal, thereby minimizing the risk of spreading CG to any healthy host 

trees in the area. Trees may be physically removed by pulling or pushing 

them out of the ground with heavy equipment, or cutting the trunk at or 

near the soil line. Regardless of the technique used, herbicides should be 

used on any sprouts that grow from roots left in the ground or from a 

freshly cut stump as these sprouts would still be infected with CG. 

APHIS’ 2006 CG disease guidelines indicate that any methods for 

disposing of infected trees that kill vectors, prevent further access to 

foliage by vectors, and prevent the use of removed trees as budwood 

sources are appropriate (Floyd and Krass, 2006). Suitable disposal 

methods include burning, chipping (only smaller diameter branches and 

foliage would need to be chipped; large diameter wood could be disposed 

of by other means), or burial in a landfill (Floyd and Krass, 2006).

APHIS has undertaken measures to control the artificial spread5

 5 Humans moving ACP host plant material have been responsible for the long-distance spread of 

ACP and CG; this is often referred to as “artificial” spread.

of ACP to 

noninfested areas of the United States in order to slow the spread of CG 

since the introduction of the disease into the country 2005. APHIS issued 

numerous Federal Orders designating all or parts of affected counties and 

States as areas quarantined for ACP and/or CG, and imposed restrictions 

on the interstate movement of all ACP and CG host plant material from 

those areas. On June 17, 2010, APHIS published an interim rule which 

codified most of the provisions of the Federal Orders into regulation. 

Under the interim rule, a State, or a portion of a State, is quarantined when 

ACP and/or CG is found. The interstate movement of ACP and CG host 

plants and plant material from quarantined areas is regulated. ACP and 

CG host plants and plant material that are to be moved interstate or 
7

immediately exported from the United States from an area quarantined for 

ACP but not CG must be treated with methyl bromide, some other 

approved treatment, or processed in a manner to eliminate the risk of 

spreading ACP and CG. Nursery stock that is to be moved interstate that 

is not treated with methyl bromide must be treated with a soil drench or an 

in-ground granular application of dinotefuran or imidacloprid followed by 

a foliar spray containing either bifenthrin, chlorpyrifos, deltamethrin, 

fenpropathrin, or an imidacloprid and cyfluthrin mixture. ACP and CG

host plants and plant material intended for consumption, for use as 

apparel, or for decorative purposes that are not treated with methyl 

bromide must be treated with irradiation or processed in a manner to 

eliminate the risk of spreading ACP and CG. Nursery stock from an area 

quarantined for CG cannot be moved interstate unless it is treated for ACP 

and is immediately exported from the United States.

The Federal Orders and interim rule focused on controlling the artificial 

spread of ACP and CG. The regulations, which established quarantines 

and regulated movement of host plants, primarily affect nursery stock 

producers (nurseries), as well as commercial retailers and distributors. 

In addition to spreading artificially, ACP and CG can spread naturally. 

The natural spread of pests is usually considered to be an increase in 

distribution that occurs without human assistance. The spread tends to 

occur via flight, wind dispersal, or transport by vectors such as insects or 

birds. While the artificial movement of ACP on host plants from nurseries 

is one concern, the natural movement of ACP within and between 

abandoned citrus groves, producing citrus groves, residential and other 

private properties, and public areas is of concern because they serve as 

potential reservoirs for infected psyllids. Therefore, in addition to the 

Federal actions taken to control the spread of psyllids from nurseries, 

some States have implemented their own additional ACP control programs 

to decrease the natural spread of ACP and CG. 

The California Department of Food and Agriculture (CDFA) issued a 

State quarantine in areas where ACP has been found. CDFA is working to 

increase surveying and trapping, and is cooperating with counties on ACP

trapping programs. CDFA is attempting to educate the public by 

providing informational materials, including mailing of postcards, posters, 

pamphlets, and Web sites. CDFA has been inspecting cargo at the State 

border for ACP and treating the cargo with insecticides if ACP is found. 

CDFA is also conducting insecticide treatments in urban and rural

residential areas on a voluntary basis if ACP is found. Treatments may 

extend up to 400 meters around each detection site. Only ACP host plants 

are treated. Both foliar insecticides (applied to plant leaves) and systemic 

insecticides (applied to the soil, taken up by the plant’s roots, and moved 

throughout the plant’s system) are applied. Foliar treatments include
8

PyGanic® (an organic formulation of a pyrethrin), Tempo® SC Ultra 

(cyfluthrin is the active ingredient), or Sevin® SL (carbaryl is the active 

ingredient). Soil treatments are conducted with Merit® 2F (imidacloprid 

is the active ingredient). Properties that are treated receive written 

notification at least 24 hours prior to treatment. Following treatments, 

CDFA leaves completion notices with homeowners, detailing precautions 

that they should take to minimize exposure (CDFA, 2010).

The University of California (UC) Integrated Pest Management Program 

(IPM) has provided treatment guidelines to citrus growers in California’s 

ACP quarantine zones. UC IPM recommends that growers treat with both 

a foliar insecticide for immediate control and a systemic insecticide for 

long-term control. A foliar treatment may be made using Danitol® 2.4 EC 

(fenpropathrin), Baythroid® XL (cyfluthrin), Delegate® (spinetoram), 

Lorsban® 4E (chlorpyrifos), Dimethoate® 400 (dimethoate), Sevin® 80S 

or Sevin® XLR Plus (carbaryl), Carzol® SP (formetanate), or 

Micromite® 80 WGS (diflubenzuron). Systemic insecticides may be 

applied using Movento® (spirotetramat) (while it is still available), 

Admire® Pro (imidacloprid), dinotefuran, or another registered systemic 

imidacloprid product, such as AliasTM 2F, Nuprid® 2F, or CourazeTM 2F 

(UC IPM, 2009). 

ACP and CG infestations are present in citrus-producing areas of Mexico 

that are in close proximity to the U.S. border. In addition, infestations in 

other citrus-producing areas within Mexico may result in movement of 

ACP into the United States via fruit shipment. Mexican infestations 

represent an additional threat to citrus-producing areas, especially those 

located near the U.S.-Mexico border. CDFA, in cooperation with APHIS 

and the Mexican government, Secretaría de Agricultura, Ganadería, 

Desarrollo Rural, Pesca y Alimentacíon (SAGARPA), have implemented 

a coordinated program to control the ACP infestation and reduce the threat 

of spreading CG. Interstate or export movement of regulated commodities 

require a certificate or permit, contingent upon the treatment of the 

commodity. Control methods that are being used within Mexico include

(1) regulatory chemicals, (2) cold treatment, (3) vapor heat treatment, and 

(4) irradiation treatment. Regulatory chemical treatments include 

fumigation with methyl bromide and foliar pesticide applications using

carbaryl, pyrethrins, cyfluthrin, bifenthrin, chlorpyrifos, deltamethrin, 

fenpropathrin, or an imidacloprid/cyfluthrin mixture. Soil drenches with a

formulation of imidacloprid or dinotefuran could be applied to provide 

systemic control of ACP. Nurseries, citrus groves, and residential 

properties are being treated. Cold treatment, vapor heat treatment, or 

irradiation treatment of certain produce, as a requirement for certification 

and shipping, must be conducted in facilities that are inspected and 

approved. APHIS is assisting SAGARPA with funding, staffing, and/or 

expertise, as necessary, to ensure that all measures are implemented and 

sustained.
9

The State of Florida uses insecticides and biological control agents to 

control ACP and the spread of CG. The University of Florida’s Institute 

of Food and Agriculture Sciences (IFAS) recommends the use of the 

following chemicals in citrus groves to treat for ACP: chlorpyrifos, 

dimethoate, fenpropathrin, imidacloprid (foliar and soil drench), phosmet, 

spinetoram, spirotetramat, thiamethoxam (foliar and soil drench), and 

zeta-cypermethrin (Rogers et al., 2009a; and Rogers et al., 2009b). No 

sprays are recommended during bloom to protect bees and other beneficial 

insects (Stansly et al., 2008). The post-bloom period is also critical for 

many natural predators of ACP and, therefore, only select insecticides 

should be used if necessary (Stansly et al., 2008). 

In 1999, the Florida Department of Agriculture and Consumer Services 

released Tamarixia radiata (T. radiata) (imported from Taiwan and 

Vietnam) as a biological control agent of ACP. T. radiata is a small, 

stingless wasp ectoparasite (an external parasitic organism) of ACPs. 

Parasitism rates have been low, averaging below 20 percent during the 

spring and summer (Qureshi et al., 2009). A wasp, Diaphorencyrtus 

aligarhensis, has also been introduced for the biological control of ACP in 

Florida; however, it has not become established in the State. 

IFAS’ CG management recommendations include treating all citrus groves 

as though they already have CG. They recommend propagation of 

disease-free nursery stock, removing trees infected with CG, controlling 

ACP populations, and, if possible, removing host plants from around 

commercial citrus groves. IFAS recommends that citrus growers scout for 

CG four times a year, and more frequently if surrounding groves have CG. 

During the spring, flush scouting becomes more difficult, and IFAS

recommends that scouts should look further into the tree canopy (IFAS, 

2009). Certain areas of Florida are treating both abandoned and producing 

citrus groves.

Texas is in the process of implementing an ACP and CG action plan that 

would include all locations where citrus is grown (e.g., citrus groves, 

abandoned citrus groves, residential citrus and public lands) (TCGTF, 

2009). Chemical treatment, monitoring, and an education and public 

outreach program are proposed in the action plan. Citrus growers would

treat for ACP based on information acquired from traps deployed in their 

groves. Growers would test for CG and would remove any diseased trees 

(TCGTF, 2009). In addition to the U.S. Environmental Protection Agency

(EPA)-registered insecticides, Danitol 2.4-EC (fenpropathrin) may be used 

for low volume ground application against ACP in Texas. The product

has been approved by the Texas Department of Agriculture under the 

Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), section 

24(c).
10

In 2009, the Texas A&M University–Kingsville Citrus Center, in 

cooperation with APHIS, implemented an ACP control research project in 

citrus groves and residential properties within Hidalgo County, Texas. 

The objective of the study was to demonstrate that ACP populations may 

be controlled in a coordinated fashion and at a regional level in managed 

and abandoned citrus groves and residential properties to lower the 

potential risk posed by CG. The research included chemical treatments of 

chlorpyrifos, citrus oil, fenpropathrin, imidacloprid, kaolin clay, neem oil, 

pyrethrin, and/or zeta-cypermethrin on citrus trees in approximately 1,400 

acres in Hidalgo, Texas, from mid-February 2009 until September 2009. 

Treatments were applied via aerial applications and ground applications. 

Researchers concluded that: 1) aerial applications of pesticides were as 

effective as ground applications at controlling ACP; and 2) covering a 

large area with pesticides in a coordinated fashion was much more 

effective at controlling ACP than a patchwork of pesticide applications 

(Sétamou et al., 2009). These studies are continuing in 2010 on 

approximately 4,700 acres in the same area; the chemicals being studied 

are the same.

In Plaquemines Parish, Louisiana, the Plaquemines Parish Council and 

citrus producers are conducting ACP suppression efforts that consist of 

two aerial applications of insecticides per year over commercial citrus

groves. The Plaquemines Parish government has funded helicopter 

spraying in conventional commercial citrus groves (LSUAG, 2009; 

Bennett, 2009). The Louisiana Citrus Spray Schedule indicates that the 

following chemicals may be utilized, depending on time of the year and 

whether the trees have bloomed: Danitol® 2.4 EC (fenpropathrin), 

Lorsban® 4E (chlorpyrifos), Sevin® XLR Plus (carbaryl), Provado® 

(imidacloprid), Mustang MaxTM (zeta-cypermethrin), and horticultural oils 

(LSUAG, 2010). The parish also treats residential properties on a 

voluntary basis with CoreTect tablets (LSUAG, 2009; Bennett, 2009) and 

Merit 2F (Bennett, 2009), which contain the active ingredient 

imidacloprid.

The Arizona Department of Agriculture maintains ACP traps and conducts 

visual inspections for the pest. The State has not published formal 

recommendations for the use of treatments against ACP; however, a CG 

task force has been formed. The Arizona Cooperative Extension (ACE) 

recommends homeowners use water or soap solutions or an insecticide to 

control ACP, and to contact ACE if symptoms of ACP occur (Begeman 

and Wright, 2009).

E. Previous Environmental Documentation

In September 2005, APHIS prepared an EA to analyze and evaluate 

potential environmental effects resulting from a Federal Order which 

would implement a CG control program in Florida nurseries (USDA–
11

APHIS, 2005a). The EA was subsequently revised and finalized in 

January 2006 (USDA–APHIS, 2006). APHIS prepared a second EA in 

October 2007 (USDA–APHIS, 2007). This EA evaluated the possible 

environmental impacts associated with revising the CG Federal Order, 

and, in particular, the treatment schedules specified within it. APHIS 

prepared a third EA in January 2009 (USDA–APHIS, 2009a) which 

evaluated the environmental impacts of implementing an ACP control 

research project in citrus groves and residential properties in Hidalgo 

County, Texas. The finding of no significant impact was amended in 2010 

(USDA–APHIS, 2010a) to discuss the 2010 research program in Hidalgo 

County, Texas. 

APHIS prepared a fourth EA in July 2009 (USDA–APHIS, 2009b). This

EA analyzed the environmental impacts anticipated from chemically 

treating ACP and CG host plants and plant material that are to be moved 

interstate or immediately exported from the United States from an area 

quarantined for ACP but not CG. The chemical treatments that were

analyzed were methyl bromide, dinotefuran, imidacloprid, bifenthrin, 

chlorpyrifos, deltamethrin, fenpropathrin, and an imidacloprid and 

cyfluthrin mixture. Irradiation of ACP and CG host plants and plant 

material intended for consumption, for use as apparel, or for decorative 

purposes that are not treated with methyl bromide was also analyzed. 

II. Purpose and Need

APHIS is responsible for taking actions to exclude, prevent, eradicate, 

and/or control plant pests, such as ACP and CG, under the Plant Protection 

Act (7 United States Code (U.S.C.) 7701 et seq.). As such, it is important 

that APHIS take the steps necessary to control CG and its vector, ACP, to 

prevent their introduction and spread into uninfested citrus growing areas 

of the country.

The purpose of a national ACP control management program is to prevent 

the introduction and further spread of CG in the U.S. citrus industry. The 

current Federal ACP and CG interim rule established the quarantine areas 

for ACP and CG, and also placed restrictions on the interstate movement 

of host plants and plant parts from the quarantined areas. The proposed 

ACP control program in citrus groves would address the risk of the natural 

spread of ACP and CG in and around commercial citrus groves.

There is a need for the program to protect the U.S. citrus industry from the 

economic damage of CG, one of the worst citrus pests in the world. The 

United States is one of the top citrus exporters in the world, ranking first 

in grapefruit, third in oranges, fifth in lemons and limes, and seventh in 

tangerines (USDA–FAS, 2010). The resources potentially at risk in the 

four largest commercial citrus-producing States (Arizona, California, 
12

Florida, and Texas) if CG were to become established in the United States

are summarized in table 1.

Table 1. Acreage and Value of Citrus Production in the Four Largest 

Producing States.

State Bearing Acres1 Production Value1 Employment2 Other Revenues2

Florida 530,900 $1.5 billion 110,500 jobs $7.5 billion

California 269,600 $1.2 billion 22,000 jobs $1.2 billion

Texas 27,300 $46.5 million 1,911 jobs $121 million

Arizona 17,900 $36.6 million n/d n/d

1 USDA–NASS Citrus Fruits 2009 Summary

2 Industry estimates based on CNAS (2007), R. Norberg (2008), Spreen et al. (2006).

In addition to the direct loss of citrus production, impacts to other 

businesses could occur from CG infestations. An economic assessment

was conducted by the Center for North American Studies (CNAS), Texas 

A&M University, on the potential economic impacts of CG in Texas. The 

assessment not only considered the effects of CG on the citrus industry,

but also how a change to the citrus industry could affect business activity, 

income, and employment in other sectors of the economy that are 

associated with the citrus industry. CNAS reported that farm and related 

sector income generated by citrus production in Texas was an annual 

average of $50.9 million for crop years 2004–05 and 2005–06. Another 

$24.5 million was generated off-farm in transportation, handling, 

processing, and marketing. Total employment associated with the Texas 

citrus industry was estimated to be 1,911 jobs (farm jobs represented the 

majority, but sorting, grading, cleaning, and packing, etc., were included). 

After 2 years of CG infestation, CNAS predicts a total income loss of 

$14.7 million and total job losses at 373. After 5 years of infestation, 

income losses were predicted to total an additional $42.6 million and job 

losses to reach 1,080. Losses in real estate, farm machinery and 

equipment, food services, medical sectors, and banking and insurance 

businesses were averaged after 2 and 5 years and were expected to reach

hundreds of thousands of dollar losses for each sector (CNAS, 2007).

The purpose of this EA is to analyze the environmental impact of an ACP 

control program throughout the continental United States and Puerto Rico.

This EA has been prepared consistent with the National Environmental 

Policy Act of 1969 (NEPA) (42 U.S.C. 4321 et seq.) and APHIS’ NEPA 

implementing procedures (7 CFR part 372). APHIS provided a 30-day 

public comment period for this EA. The comment period ended on 

September 26, 2010. APHIS received three comments. As a result, minor 

editorial revisions were made to this EA.
13

III. Affected Environment 

The area that could be affected by the proposed action, USDA 

participation in a cooperative Federal, State, and industry ACP and CG 

management program, includes all the counties with commercial citrus 

production in Arizona, California, Florida, Louisiana, and Texas (see

appendix C for a map of the counties). In addition, the Commonwealth of 

Puerto Rico produces citrus commercially and has both ACP and CG and,

therefore, is included in the affected area. Theoretically, ACP can survive 

in a larger area than that in which citrus is grown commercially. Indeed, 

ACP has been found in nonagricultural areas in Alabama, Georgia, 

Mississippi, and South Carolina. However, some areas that could harbor 

populations of ACP are not of interest to the cooperative management 

efforts because, even if infested with ACP, it is unlikely that they would 

host CG and potentially affect commercial citrus. This may be because 

these areas are many miles away from the nearest commercial citrus, or 

they are separated from commercial citrus by unsuitable desert habitat 

which effectively isolates the ACP population from areas where ACP or 

CG could become an economic issue. Therefore, to insure that all areas 

that could reasonably harbor ACP and host CG and be expected to serve 

as reservoirs of ACP (which could spill into commercial areas) are 

included within the program area; the affected area has been identified to 

be larger than the sum of the areas in which commercial citrus is grown. 

The area that is considered to be the affected environment is displayed in a 

map in appendix D. 

 

IV. Alternatives

A. No Action

Under the no action alternative, APHIS would not participate with the 

citrus-producing States or industry to implement a coordinated and 

cooperative program to control ACP or prevent CG. There would be no 

Federal funding, staffing, or other assistance to combat ACP and CG. The 

result would likely be that each State implements a separate program. 

This will result in a fragmented approach that lacks national coordination 

and leveraging of resources across States and, therefore, reduced 

effectiveness and efficiency. APHIS’ only involvement would be to 

maintain the current quarantine for ACP and CG. Under this scenario, 

ACP would spread unchecked to all areas of the United States where hosts 

are present, thus increasing the likelihood that CG would be introduced, 

spread and, perhaps, become established throughout the United States. 
14

B. Cooperative Federal, State, and Industry ACP and

CG Management Program 

Under this alternative, APHIS, States, the citrus industry, and other 

stakeholders would implement a cooperative program designed to 

suppress ACP and, hence, prevent or slow the spread of CG into citrusproducing areas. APHIS will provide the overall national coordination 

and technical support to cooperating States and stakeholders. The goal is 

to leverage resources of Federal and State agencies and industry 

organizations to optimize the overall effectiveness of program delivery. 

APHIS has assembled a number of working groups consisting of 

representatives from Federal and State agencies and industry 

organizations, to coordinate the overall implementation of the program, 

including research, communication and outreach, and regulatory issues. 

The U.S. citrus industry has also created the National Citrus Health 

Response Program Council (National CHRP Council) which consists of 

representatives from citrus-producing organizations from each State. The 

National CHRP Council serves as the liaison for the citrus industry, and 

provides leadership and coordination of industry resources in support of 

the program.

In addition to the technical support and the overall coordination of the 

program, USDA will provide funding and other resources to cooperating 

States in support of program implementation. These resources would be 

used in support of field operations, including survey, diagnostics, control, 

and public education and outreach. 

The strategy is to contain, control, and suppress ACP populations where 

they are known to be present through timely, targeted, and coordinated 

treatments. While the majority of the treatments would be confined to 

commercial citrus groves, some treatments may also occur in noncommercial citrus sites. Treatments in noncommercial sites are designed 

to prevent ACP populations from spreading into commercial citrusproducing groves and are implemented under the supervision of State and 

local authorities. Treatments in the commercial citrus-producing groves 

would be applied in accordance with pesticide label requirements and 

would be paid for and conducted by the growers in a well-coordinated 

fashion and timed prior to tree flush cycles. Growers in the affected 

areas have or are in the process of establishing pest management 

districts/regions that would be responsible for coordinating all treatments 

in commercial settings. All program activities would be implemented in 

cooperation with State and local authorities, as well as growers. This will 

help contain, control, and suppress ACP populations in a coordinated 

fashion and, therefore, prevent or slow the spread of CG into healthy 

commercial citrus-producing areas and groves. 

1. Strategy
15

Surveillance activities would be carried out by Federal, State, and local 

personnel in order to detect the presence of ACP and CG. A number of 

survey methods and tools have been identified, including visual inspection 

of host plants, mechanical suction devices (P-vac), sweepnets, tap 

sampling, and traps. Trapping is be the most common method as it is used 

for early detection in areas where ACP has yet to be detected or to delimit 

newly discovered infestations. In areas where ACP is known to be 

present, traps would be used to evaluate the effectiveness of the control 

actions. Traps are serviced by Federal, State, or local agricultural 

inspectors. The trap used for ACP detection is a two-sided board coated 

with StickumTM. ACPs are caught on the sticky surface. Detection and 

delimitation surveys would be conducted in residential, urban, and rural 

areas. USDA–APHIS has established survey protocols that will provide 

guidelines and standards to be implemented across all program areas. 

Accurate and timely identification of ACP and diagnostics of CG is

essential. Critical programmatic activities and decisions, including 

determining survey and timely control measures, are based on accurate 

identification. Identification of ACP is especially important in a new area 

where the disease is not known to occur. Increased surveillance for CG 

may be undertaken in these areas once ACP is confirmed. APHIS has 

established a network of laboratories strategically located to provide the 

identification and diagnostic support for the program. (Identification and 

diagnostics include confirmation of ACP, and testing of psyllid and plant 

tissue samples for the possible presence of CG.) In areas where ACP or 

CG is detected for the first time, confirmatory diagnostics must be 

conducted through the APHIS National Identification Services. 

USDA–APHIS has established the Communication and Outreach Working 

Group, which consists of representatives of communication professionals 

from APHIS, cooperating States, industry, and stakeholders. The group is 

responsible for coordinating timely and accurate information about the 

program and the threat that ACP and CG can impose on the U.S. citrus 

production. The working group has developed a communication plan in 

an effort to prevent the further spread of citrus pests and diseases. The 

primary goal of the plan is to increase public awareness (particularly 

among travelers and online consumers) of the potential risks associated 

with moving citrus plants and products. In addition, each State task force 

convenes routine meetings to inform members of the citrus and nursery 

industries and local communities about pests and diseases of concern, 

requirements associated with the quarantines that are in place to ensure 

compliance, and the activities that are ongoing to limit the spread of citrus 

pests and diseases. In addition, the communication plan includes 

providing the information through various communication channels, 

including prints (pamphlets), online (Web sites), and targeted TV public 

announcements and advertisements. 

2. Surveys

4. Public 

Education

and Outreach

3. Diagnostics
16

Two application strategies will be used for chemical control of ACP. 

Foliar sprays will be used for immediate reduction of ACP populations. 

Soil applications will also be used to provide longer lasting, systemic ACP 

control. Commercial citrus groves may be treated with a soil drench or 

in-ground granular pesticide application followed by a foliar spray. 

Table 2 provides a list of pesticides that may be recommended for use in 

the program. All formulations of insecticides used in the program must be 

registered by EPA under FIFRA. In commercial treatments, all chemical

treatments would be conducted by the commercial growers or certified 

applicators and paid by the growers. 

Treatments in settings other than nurseries or citrus groves, such as 

residential and public properties, would occur under State authority upon 

the detection of one or more ACP. Indications from potential State 

cooperators are that residential and other noncommercial insecticide 

applications are likely to take place in Arizona, California, Louisiana, and 

Texas. At the present time, Florida and Puerto Rico have no plans to treat 

noncommercial sites; however, this may change in the future depending 

upon the needs of the cooperators, and expert advice and opinions. If 

residential treatments are made, they are likely to be on a voluntary 

basis—that is, the resident would agree to allow the State or their

cooperators to conduct the treatment. The treatment area may extend up 

to 400 meters around each find of ACP. The current ACP programs in 

California and Mexico apply an insecticide to ACP host plants within 

400 meters around each ACP find. Only ACP host plants would be 

treated. Noncommercial site treatment options, under State authority,

include both foliar and systemic insecticides. 

a. Foliar Treatments 

Foliar treatment may commence upon the detection of ACP to target the 

adult life stage of the pest using one or more of the following 

insecticides—

1) Carbaryl - may be applied to all host plants within an area up to a 

400-meter radius of the find sites using hydraulic-spray or hand- spray 

equipment. According to label directions, treatments may be repeated

every 10 to 14 days; or

2) Cyfluthrin - would be applied a minimum of one time to the foliage of 

host plants at designated residential and noncommercial properties. 

The chemical may be applied to all host plants in an area up to a 

400-meter radius of the find sites using hydraulic-spray or hand-spray 

equipment; or 

3) Pyrethrin - an organic formulation of the chemical may be applied 

according to label instructions to all host plants in an area up to a 

5. Chemical 

Treatment 

for ACP
17

400-meter radius of the find sites, using hydraulic spray or hand spray 

equipment. Treatments may be repeated according to label directions. 

Table 2. Potential Insecticides and Use Sites.

Potential Chemical

Potential Use Site

Commercial and 

Abandoned Groves

Noncommercial Sites

SOIL DRENCH or IN-GROUND GRANULAR

Dinotefuran X X

Imidacloprid X X

Thiamethoxam X ----

FOLIAR (AIR OR GROUND)

Abamectin X ----

Azadirachtin X ----

Bifenthrin X ----

Carbaryl X X

Chlorpyrifos X ----

Citrus Oils X ----

β-Cyfluthrin X X

Deltamethrin X ----

Diflubenzuron X ----

Dimethoate X ----

Fenpropathrin X ----

Formetanate X ----

Imidacloprid/Cyfluthrin X ----

Kaolin Clay X ----

Malathion X ----

Petroleum Oils X ----

Phosmet X ----

Pyrethrin X X

Spinetoram X ----

Spirotetramat X ----

Thiamethoxan X ----

Ζeta-Cypermethrin X ----

b. Systemic Treatments 

Soil treatments are also conducted upon the detection of ACP to target the 

immature life stages, such as eggs and nymphs, using the insecticide 

imidacloprid or dinotefuran. These treatments are applied to soil beneath 

the drip line of host plants a minimum of one time and a maximum of 

twice a year. 
18

Affected residential and noncommercial properties would be notified in 

writing at least 24 hours prior to treatment. Following treatment, 

completion notices would be left with homeowners detailing precautions 

to take and postharvest intervals applicable to any fruit on the property. 

Treatments may be repeated at intervals prescribed on the label if live 

psyllids are found upon reinspection.

Biological control organisms of ACP (including insect-attacking mites, 

insects, and pathogens) would be incorporated into the program as they 

become available to reduce the severity of infestations of ACP in the 

United States. Biological control organisms would be targeted for use in 

urban and natural settings and certified organic farms where insecticides 

are not feasible to apply. They might also be used in infested abandoned 

groves where industry or State cooperators cannot spray due to funding, 

logistical reasons, or other issues. 

As required by the interim rule published in the Federal Register on June 

17, 2010, a quarantine would be established under APHIS and State

authority if one or more ACP is found in an area. All articles capable of 

harboring ACP would be regulated in accordance with the recently 

published interim rule (available under Federal Regulations at 

http://www.aphis.usda.gov/citrusgreening). Prior to movement out of 

quarantined areas, nursery stock may also be treated with methyl bromide 

in accordance with 7 CFR part 305. A technical working group 

recommended that areas quarantined for ACP remain so for a minimum of 

four flush cycles (approximately 18 months to 2 years) before deregulating 

the area.

V. Environmental Consequences

A. No Action

Under the no action alternative, APHIS would not participate with the 

citrus-producing States or industry to implement a coordinated and 

cooperative program to control ACP or prevent CG. There would be no

Federal funding, staffing, or other assistance to combat ACP or CG. The 

result would likely be that each State would implement a separate 

program. This will result in a fragmented approach that lacks national 

coordination and leveraging of resources across States and, therefore, 

reduced effectiveness and efficiency. 

APHIS’ only involvement would be to maintain the current quarantine for 

ACP and CG. Under this scenario, it is doubtful that a successful ACP 

control program could be instituted or sustained in all of the affected 

States, thus increasing the likelihood that CG would be introduced and, 

perhaps, become established throughout the United States. This would 

7. Quarantine

6. Biological 

Control of 

ACP
19

first occur in areas where CG has been determined to be present (Florida, 

Georgia, Louisiana, Puerto Rico, U.S. Virgin Islands, and South Carolina). 

Depending upon the degree of success of the efforts of individual States 

and individual farmers, CG will likely spread throughout the remainder of 

the citrus belt negatively affecting U.S. citrus production (including fruit, 

juice, and citrus byproducts) and the ability to market citrus in the world 

marketplace. APHIS staff estimates show revenues of $3 billion 

(packinghouse door equivalents) generated by citrus fruit production could 

rapidly decrease, along with the potential loss of more than 30,000 jobs 

associated with planting, grove maintenance, and crop harvest. Another 

220,000 jobs and lost revenue could result from infection of nursery stock, 

closure of fruit processing and packaging facilities, and halting production 

of cartons and containers, transportation, marketing, shipping/distribution, 

and retail sales currently valued at more than $13 billion per year. 

B. Cooperative Federal, State, and Industry ACP and 

CG Management Program

The environmental impacts of the survey, identification and diagnostics, 

public education and outreach, and strategy aspects of the proposed 

cooperative ACP management and control program are expected to be 

minimal. Survey will involve an increased physical presence in the field 

to place and monitor traps; however, the increased effort will not provide a 

discernible increase in environmental impacts to either commercial areas 

or noncommercial and residential areas because human activity is more or 

less constant in these areas, and no lasting pollutants are distributed 

throughout the potential impact area. 

Diagnostics and public education will not result in a discernible impact to 

the environment, although, in a cumulative sense, an increase in public 

education could raise public awareness of the problems and issues 

surrounding ACP control and CG eradication efforts.

Impacts that could be associated with the implementation of the ACP 

control strategy are likely to be minimal. The strategy will result in a 

regionally coordinated approach to ACP control. The coordinated 

approach is likely to result in local shifts in pesticide usage, with use of 

some insecticides increasing and some decreasing. The coordinated 

approach, however, should result in a more effective and efficient way to 

control ACP than individual and independent controls by growers would 

offer. From that standpoint, over the long term an effective, coordinated 

control program for ACP and CG is likely to result in reduced impact to 

natural resources and to the economic health of the citrus industry. In the 

short term, nonagricultural properties that may be included in the program 

may receive insecticide treatments that they would otherwise not have 

received. Some properties that may receive treatments under this program 

1. Survey, 

Identification 

and 

Diagnostics, 

Public 

Education

and 

Outreach, 

and Strategy 
20

would not ordinarily be treated. If left untreated, these properties could 

then serve as reservoirs for repopulating the surrounding areas after they 

have been treated, thus reducing the effectiveness of the treatments. For 

those properties that would have received treatments with or without this 

program, their treatments will be coordinated with those of surrounding 

properties and, thus, are likely to be more effective at reducing local ACP 

populations.

Most insecticide treatments will be conducted and funded by the growers

in commercial citrus groves. APHIS’ involvement with insecticide 

application is primarily one of providing advice to growers and 

cooperators. Where the State cooperators have determined it to be 

important to the ACP control efforts, they may apply chemical treatments 

to host plants in residential and noncommercial areas, and possibly to 

abandoned orchards in close proximity to commercial production areas. 

Any insecticides used by State cooperators, and those recommended for 

use by APHIS and State cooperators for commercial citrus grove 

applications, will be determined on a regional basis after consideration of 

typical pesticide use in the area, advice of ACP control experts, other 

agricultural experts, and review of EPA-approved insecticides and uses. 

All uses will be in accordance with EPA-approved pesticide labels. 

Experts within each of the potential cooperating States regularly provide 

their recommendations to State departments of agriculture and to APHIS. 

Each of the insecticides proposed for use has distinct characteristics that 

will be considered prior to making any recommendations. The 

insecticides listed in table 2 are those that may be recommended for use. 

A summary of their potential for environmental and human health impact 

follows.

Human Health, Nontarget Toxicity, and Risk of Program 

Insecticides

For program insecticides restricted to applications in citrus groves, 

potential human-related exposure during applications would be restricted 

to workers and applicators at the time of application. Protective gear, 

safety precautions required on the label, State law, and standard program 

operating procedures are designed to ensure that no adverse effects to 

applicators are expected (USDA–APHIS, 2005b). 

All insecticides that are recommended in the proposed program are 

currently registered by EPA for use on citrus. As long as they are used in 

accordance with their labels, the legal residue tolerances established by 

EPA are not expected to be exceeded. However, the area-wide 

coordination established by the proposed program could result in more 

effective ACP control and, ultimately, result in reducing the total number 

of applications and their associated residues. EPA sets residue tolerances 

at levels where they are confident that they pose minimal, if any, risk to 

2. Chemical 

Treatments for 

ACP Control
21

people. Applications made in accordance with the label directions, 

including harvest and reentry intervals, and washing and disinfection of 

fruit at packinghouses reduces public exposure so that it is below tolerance 

limits and is unlikely to be harmful to the public. In addition, during 

treatments of residential areas, human exposure to program insecticides is 

minimized through adherence to recommended practices at the time of 

program control applications. 

For all insecticide applications in citrus groves, there is the potential for 

indirect risk to wild mammals and birds from the loss of available 

invertebrate prey that would occur after treatment. Risks from these types 

of effects are reduced for those birds and mammals that can forage outside 

of the treatment area and recovery of most invertebrate populations that 

will occur within the citrus groves after treatment will ensure that any 

impacts to mammals and birds are short-term in nature. The extent and 

time for recovery would be based on how persistent and broad spectrum a 

selected insecticide may be in its nontarget effects. 

a. Dinotefuran (Citrus Groves)

(1) Human Health Toxicity and Risk

Dinotefuran is a systemic insecticide belonging to the neonicitinoid class 

but within the nitroguanidine subclass. Dinotefuran has moderate acute 

toxicity to mammals, and low inhalation and dermal toxicity. It is not 

considered a skin irritant based on skin sensitization and irritation studies; 

however, it is considered an eye irritant. Based on sublethal study results,

dinotefuran is not considered a carcinogen or mutagen; developmental 

effects only occur at doses that are maternally toxic. Immune- and 

endocrine-related effects have been observed in multiple studies (EPA,

2004a). These effects were observed during prolonged exposures and are 

not anticipated in this program. The primary immune system-related 

effect observed in the studies was altered thymus weights which may not 

be related to direct immune toxicity of dinotefuran. However, this may be 

a secondary effect due to overall reduced body size and weight gain during 

exposures that were 13 weeks or greater, depending on the type of study. 

Based upon EPA’s evaluation of risk to different human population 

subgroups, including occupational exposures, it was determined that the 

dinotefuran risk alone, as well as aggregate risk when including other 

neonicitinoid insecticides, did not exceed agency levels of concern (EPA,

2004a). 

Due to the mobility and persistence of dinotefuran, there is the potential 

for surface and ground water residues to occur in areas that are vulnerable 

to runoff and leaching. Adherence to label requirements and avoidance of 

dinotefuran applications to permeable soils will reduce the possibility of 

contamination of any drinking water resources. Due to the systemic 
22

nature of dinotefuran, there is the possibility of residues in citrus harvested 

for human consumption. The low residues that have been observed with 

similar insecticides in citrus, and the low toxicity to mammals suggest that 

adverse effects would not be expected for people that would consume

citrus from groves treated with dinotefuran. 

(2) Nontarget Toxicity and Risk

Dinotefuran has low to moderate acute and chronic toxicity to nontarget 

wildlife, such as mammals and birds. Direct risk is not expected based on 

conservative estimates of exposure and the available toxicity data. 

Indirect impacts to wildlife populations through the loss of invertebrate 

prey are also not expected to be significant because only sensitive 

terrestrial invertebrates that feed on treated trees will be impacted while 

other insects would be available as prey items. Dinotefuran toxicity is 

high for honey bees and, similar to other neonicotinoid insecticides, there 

is uncertainty regarding the impacts of residues from this class of systemic 

insecticides in pollen and nectar. Studies measuring pollen and nectar 

residues in other crops with imidacloprid, a neonicotinoid insecticide, 

have shown that sublethal effects occur above residues measured in the 

field. However, there is uncertainty regarding dinotefuran residue levels 

in pollen and nectar from citrus trees and potential impacts to honey bees. 

Dinotefuran has low toxicity to fish and most aquatic invertebrates with 

the exception of some marine invertebrates where it is considered highly 

toxic. Available toxicity data indicate that degradates of dinotefuran are 

less toxic to aquatic organisms. Dinotefuran is susceptible to runoff which 

could occur in aquatic areas adjacent to citrus groves. Significant drift to 

sensitive aquatic habitats is not expected based on the method of 

application. Exposure and risk to aquatic organisms will be minimized by 

adherence to label requirements regarding applications near water. Risk is 

expected to be minimal to fish, although there is a possibility of risk to 

some sensitive aquatic invertebrates in very shallow water bodies adjacent 

to treated citrus groves.

The solubility and soil adsorption characteristics of dinotefuran suggest

that it is highly mobile. Dinotefuran does not break down in water, but is 

somewhat susceptible to microbial degradation and is very sensitive to 

photolysis. Because of the high mobility and solubility of dinotefuran, 

there is the potential for leaching into ground water; however, avoiding 

application to permeable soils and areas where the water table is high will 

mitigate the potential for contamination. Dinotefuran is not expected to 

impact air quality based on the method of application and chemical 

properties which suggest a low potential for volatilization.
23

b. Imidacloprid (Residential/Citrus Groves)

(1) Human Health Toxicity and Risk

Imidacloprid belongs to a class of insecticides, called neonicotinoids,

which act by binding directly to the acetylcholine binding receptor. 

Imidacloprid is a chemical that has systemic transport qualities in plants 

which make it efficacious against psyllids and other sucking insects when 

it is applied as a soil drench or tablet treatment to soil. The acute oral 

median lethal toxicity of imidacloprid is considered to be moderate to 

mammals. Inhalation and acute dermal toxicity are considered to be low. 

The formulation of imidacloprid to be used in the program is of 

comparable or lower toxicity than the active ingredient. The program 

applications pose no evident dermal irritation or sensitization, and only 

mild eye irritation. The acute reference dose (RfD)

6 was set at 

0.14 mg/kg/day based on results from an acute neurotoxicity study in rats 

(EPA, 2003a). The primary metabolites and degradation products of 

imidacloprid are of lower toxicity than the parent compound, based on 

available data. Imidacloprid is rapidly excreted by mammals. Synergism 

of the toxicity of imidacloprid from program use is not expected due to its 

unique mechanism of toxic action which differs from other chemicals 

likely to be applied in the program area. 

Chronic studies of oral exposures to the rat were found to have a NOEL of 

5.7 mg/kg/day and a LOEL of 17 mg/kg/day. Uncertainty factors were 

applied to this NOEL to determine a chronic RfD7 for imidacloprid of 

0.057 mg/kg/day (EPA, 2003a). An acute population-adjusted RfD of 

0.14 mg/kg/day was determined, based upon a rat neurotoxicity study. 

Reproductive and developmental toxicity studies in rats found a NOEL of 

13 mg/kg/day based upon decreased body weights in both genders before 

mating, and in pups from two litters in a two-generation study. Based 

upon several in vitro8 and in vivo studies, imidacloprid is not considered 

to be mutagenic or genotoxic.9

 EPA has classified imidacloprid in

Group E in regard to carcinogenic potential. This indicates that the 

submitted studies provide evidence of noncarcinogenicity to humans. 

In this program, imidacloprid is applied as a soil drench. Exposure of 

applicators via inhalation, dermal contact, and oral intake to the active 

ingredient in these formulations is minimal due to the method of 

application, large droplet size, personal protective equipment, and the 

 6 The acute reference dose is defined by EPA as an estimate of a daily oral exposure for an acute 

duration (24 hours or less) to humans that is likely to be without risk of adverse health effects over a 

lifetime.

7 The chronic reference dose is defined by EPA as an estimate of a daily oral exposure for a chronic 

duration (up to a lifetime) to humans that is likely to be without risk of adverse health effects over a 

lifetime.

8 An artificial environment outside the living organism. 9 Chemicals capable of causing damage to DNA.
24

environmental fate of imidacloprid. Potential acute and chronic exposure 

scenarios indicate minimal risk to workers (USDA–APHIS, 2008). 

Notifications to residents include recommendations to avoid exposure to 

pesticide residues. All calculated risks for children and adults exposed to 

contaminated water and fruit residues were at least two orders of 

magnitude below those of concern for both acute and chronic exposures 

(USDA–APHIS, 2008). In addition, risks to the general population that 

would consume treated citrus from orchards that received applications of 

insecticides would be low due to the timing of application relative to 

harvest and the low residues that have been detected in citrus after 

applications of a systemic insecticide, such as imidacloprid (Ortelli et al., 

2005; Blasco et al., 2006). Any residues that would be detected in citrus 

harvested from these orchards are expected to be well below levels of 

concern for both adults and children and within the tolerances set by EPA. 

(2) Nontarget Toxicity and Risk

Imidacloprid is considered to have moderate toxicity to mammals but is 

considered toxic to birds, with acute oral median lethal toxicity values 

ranging from 41 to 152 mg/kg. The limited applications to specific citrus 

host plants will result in potential effects to invertebrates that are likely to 

be localized. Concerns have been raised about potential lethal and 

sublethal effects to honey bees and other pollinators. Median lethal 

toxicity values of imidacloprid have been based upon oral or contact 

exposure. Laboratory and field studies of honey bees indicate a lack of 

adverse effects at test concentrations comparable to realistic exposure 

scenarios, and adverse health impacts to hives only with greater exposures 

(USDA–APHIS, 2008). 

Exposure to wild mammals and birds from applications of imidacloprid 

and associated residues is not expected to occur at levels that could result 

in significant risk in residential applications (USDA–APHIS, 2008). The 

terrestrial insects that feed upon vegetation of those host plants that have 

been treated with soil drench applications are likely to be impacted, but 

the effects would be restricted to the areas of treatment. Any predatory or 

parasitic insects that depend upon ACP would also be affected due to loss 

of prey. In residential applications, mammals and birds that feed on 

insects would not depend exclusively upon the affected insects and would 

be expected to expand their foraging range to ensure adequate 

consumption. In citrus grove applications, the potential impacts to 

wildlife from loss of invertebrate prey would be greater than those in 

residential applications due to a larger treatment area. 

Aquatic vertebrates and invertebrates can be exposed through runoff or 

drift from the site of application. Significant drift is not expected from 

soil drench applications. Soil drench applications are not expected to 

result in toxic effects to aquatic vertebrates, but could pose a risk to the 
25

most sensitive aquatic invertebrates under conservative exposures 

(USDA–APHIS, 2008). Adherence to label requirements will minimize 

the risks to aquatic resources from these types of applications. 

The half-life of imidacloprid in soil under field conditions ranges from 

7 to 107 days. Imidacloprid does not adsorb strongly to soil particles. 

Imidacloprid is soluble in water and has a half-life under natural light of 

less than 5 hours in water. Based on the chemical properties of 

imidacloprid, there is the potential for leaching into ground water 

resources. Adherence to label requirements, as well as the avoidance of 

applications to permeable soils and/or areas where the water table is high, 

will ensure the protection of ground water. Imidacloprid is not expected

to impact air quality because the method of application will not result in 

significant drift. Volatilization to the atmosphere is also not anticipated, 

based on the chemical properties of imidacloprid.

c. Thiamethoxam (Citrus Groves)

(1) Human Health Toxicity and Risk

Thiamethoxam is a neonicotinoid insecticide that has activity against 

chewing and sucking insects on a variety of crops. Thiamethoxam acts by 

inhibiting nicotinic acetylcholine receptors in the insect nervous system. 

The primary metabolite of thiamethoxam is another neonicotinoid 

insecticide, clothianidin. Thiamethoxam has low to moderate acute 

toxicity to mammals in oral exposures, and has low dermal and inhalation 

toxicity. The technical material is not irritating to the skin and is a mild 

irritant to the eye (EPA, 2010b). Formulations proposed for soil and foliar 

applications have low oral, dermal, and inhalation toxicity, and are 

considered mild eye and skin irritants. Available mammalian studies 

suggest that effects occur primarily to the liver, kidney, testes, and blood 

in different test animals and exposures. Developmental effects have been 

observed in rat studies; however, effects were observed at doses that are 

maternally toxic. Thiamethoxam is not considered mutagenic and is not 

considered to be carcinogenic (EPA, 2010b).

Applications will be restricted to either foliar or soil applications in 

commercial citrus groves. Workers and applicators will be the population 

segment at greatest risk of exposure to thiamethoxam applications. 

Precautionary label language and personal protective equipment 

requirements will reduce exposure and risk to this group of the population. 

Thiamethoxam exhibits chemical properties that could result in the 

contamination of surface and ground water resources that may be used for 

drinking water. The potential for this type of exposure is reduced by 

following label recommendations regarding avoiding applications to soils 

that are highly permeable or poorly drained, and the use of vegetative 

filter strips between areas of application and aquatic resources. 
26

(2) Nontarget Toxicity and Risk

Thiamethoxam has low to moderate toxicity to nontarget wildlife, such as 

birds and mammals (EPA, 2010a, and 2010b). Thiamethoxam is toxic to 

honey bees based on available toxicity data resulting in label language 

designed to reduce exposure and risk to these types of pollinators (EPA, 

2010b). Thiamethoxam is also expected to impact other sensitive 

nontarget terrestrial invertebrates; however, these impacts will typically be 

confined to areas within the orchard. Impacts to nontarget terrestrial 

invertebrates adjacent to the orchard are not expected for soil treatments,

and foliar application exposure will be reduced by avoiding drift into 

nontarget areas.

Thiamethoxam toxicity to fish is considered low, while toxicity to aquatic 

invertebrates ranges from low to highly toxic, depending on the test 

organism (EPA, 2010b; Barbee and Stout, 2009). Toxicity to aquatic 

invertebrates, such as freshwater cladocerans, is low, while toxicity to 

aquatic insects is high with median lethality and sublethal effect values in 

the low parts per billion range (EPA, 2010b). Exposure and risk to aquatic 

organisms from thimethoxam, and the associated metabolite clothianidin, 

can be reduced by avoiding applications under conditions that would allow 

for runoff and drift.

Thiamethoxam degradation in soil is slow with half-lives ranging from 

approximately 30 days to greater than 100 days (Mainfisch et al., 2001). 

In areas where soil treatments occur within citrus orchards, there could be 

some impacts to soil quality, particularly to organisms that may be 

sensitive to thiamethoxam. For foliar treatments, potential soil-related 

impacts will be minimized by making applications that reduce the 

possibility of off-site movement. Thiamethoxam is highly water soluble 

and exhibits chemical properties that suggest it could move off-site 

(Mainfisch et al., 2001). Precautionary language on the label, as well as 

avoiding applications to soils that are poorly drained, sloping towards 

aquatic areas, or where there is a high water table, will reduce the potential 

for impacting surface and ground water quality. Impacts to air quality are 

not expected from thiamethoxam soil applications, based on the method of 

application, and foliar applications are only expected to impact air quality 

during application. Thiamethoxam does not readily volatilize into the 

atmosphere, suggesting that any impacts to air quality would be primarily 

confined to treated areas during foliar applications. 

d. Abamectin (Citrus Groves)

(1) Human Health Toxicity and Risk

Abamectin is a mixture of two avermectin compounds that are derived 

from the bacterium Streptomyces avermitilis. These products have 
27

insecticidal properties that are used to control a variety of pests in 

agricultural and nonagricultural applications. As a technical material, 

abamectin is considered highly toxic to mammals from ingestion with 

median lethality values ranging from 4.4 to 14.9 mg/kg (EPA, 2004b). 

Comparable studies with the formulated material show lower toxicity from 

oral exposures. Inhalation and dermal toxicity is much lower with median 

lethality values typically higher than the highest concentration tested. 

Depending on the formulation, or whether testing the technical material, 

skin and eye irritation is considered mild to moderate. Abamectin is not 

considered mutagenic or carcinogenic based on long-term laboratory 

studies with the mouse and dog. In studies using the rat, abamectin has 

been shown to be teratogenic at doses that also result in maternal toxicity. 

Reproductive effects, such as decreased pup weight, increased stillbirths, 

and decreased lactation have also been noted in studies at dose levels of 

0.40 mg/kg/day (EPA, 2004b).

Abamectin will be applied in citrus groves using aerial or ground 

equipment where significant exposure to the public is not expected. 

Exposure and risk will be greatest for workers and applicators during the 

time of application. Impacts to drinking water resources are not expected. 

Abamectin has very low solubility in water and adheres strongly to soil 

and sediment and, therefore, it would not be expected to leach to ground 

water or be present in surface water. Adherence to label requirements 

(such as spray drift management requirements and buffer zones from 

aquatic areas) will further reduce the threats to surface water that may be 

used as a source of drinking water. 

(2) Nontarget Toxicity and Risk

Abamectin acute oral toxicity is high to wild mammals based on 

laboratory data using the technical material. However, the various 

formulations available for use against ACP in citrus demonstrate an 

approximate ten-fold reduction in acute oral toxicity. Available data for 

the technical and formulated material indicate that dermal and inhalation 

toxicity to wild mammals is low. Developmental and reproductive effects 

have been noted in longer term studies at concentrations greater than 

1 mg/kg/day. Toxicity to birds is low with median lethal dietary toxicity 

values of 383 and 3,102 ppm for the bobwhite quail and mallard, 

respectively (EPA, 2010a). Indirect impacts to mammals and birds that 

depend on invertebrate prey items could occur after abamectin treatment 

in citrus groves. Abamectin is considered highly toxic to honey bees and 

other nontarget terrestrial invertebrates (EPA, 2010a). Adherence to label 

requirements regarding the protection of honey bees will reduce the 

impact. 

Abamectin is highly toxic to fish and aquatic invertebrates. The range of 

concentrations that cause direct mortality to fish from abamectin exposure 
28

is in the low-ppb range, while the range of sensitivities to aquatic 

invertebrates is greater because of a larger number of tested species. 

Toxicity values for aquatic invertebrates vary from the high-ppt range, 

with freshwater crustaceans being the most sensitive, to the least tolerant 

species (eastern oyster) with effect concentrations in the mid-ppb range 

(EPA, 2010a). Abamectin exposure in aquatic systems would be expected

in situations where aquatic invertebrates occur in proximity to citrus 

groves. Low application rates and the environmental fate of abamectin, 

such as low water solubility and a strong affinity to soil and sediment, 

would result in low residues in water, and reduce the potential for adverse 

impacts to fish and aquatic invertebrates. Required application buffers 

and other drift reducing measures listed on the labels for this insecticide 

will further reduce the risk to aquatic resources. 

Impacts to air quality from abamectin treatments will be limited to the 

time of application within the citrus grove. Abamectin does not exhibit 

environmental fate or chemical properties that suggest that it would 

volatilize into the atmosphere. Impacts to soil quality would be limited to 

those areas of treatment within the groves. Abamectin has a variable halflife in soil, depending on the degradation process, and can range from a 

few hours in the presence of light to approximately 60 days under dark, 

aerobic conditions. Abamectin is not expected to impact ground or 

surface water because of label restrictions for each formulation near 

surface water and the environmental fate for this class of insecticides. 

Due to the very low solubility and strong tendency to bind to soil, 

abamectin is not considered mobile and would not move to ground water 

resources. Its presence in surface water would be short lived because it 

would bind to sediment, and it is also sensitive to photodegradation in 

water with a reported half-life of less than a day. Degradation in sediment 

is slightly slower with half-lives ranging from 2 to 4 weeks. 

e. Azadirachtin (Citrus Groves)

(1) Human Health Toxicity and Risk

Neem oil is an extract from the neem plant that contains azadirachtin,

which has insecticidal properties by disrupting insect molting by acting as 

an ecdysone antagonist. The formulated material has very low acute oral, 

dermal, and inhalation toxicity, with all median lethality values greater 

than the highest concentration tested. It is considered a mild skin irritant 

but is not an eye irritant or a skin sensitizer. Azadirachtin is not 

considered mutagenic or carcinogenic, according to the data provided on 

the material safety data sheet. 

Exposure and risk to humans from neem applications are expected to be 

minimal. An aerial or ground application would occur within established 
29

citrus groves where exposure would be greatest for workers and 

applicators. The low toxicity and adherence to label requirements would 

minimize risk to this segment of the population. Azadirachtin is not

expected to be a threat to surface drinking water or ground water based on

its low solubility and binding to soil which would suggest that leaching 

into ground water is not likely, and any surface water residues would 

dissipate quickly. 

(2) Nontarget Toxicity and Risk

Azadirachtin is considered practically nontoxic to birds, with reported 

median lethality values greater than the highest test concentration. It is 

considered moderately toxic to some terrestrial invertebrates, including 

honey bees. Significant exposure and risk to terrestrial vertebrates are not 

expected from the use of azadirachtin because of its low toxicity and low 

exposure to treated vegetation or invertebrates. Indirect risk to vertebrates 

that use invertebrate prey as a food source would be low because

azadirachtin is selective in its impacts to terrestrial invertebrates. 

Azadirachtin is considered toxic to aquatic organisms, with median 

lethality toxicity values ranging from the low ppb to low ppm (EPA, 

2009a). Azadirachtin exposure in aquatic habitats could occur where they 

are in close proximity to citrus groves. The potential for these types of 

impacts to aquatic resources will be greatest in shallow, static water 

bodies, although adherence to label requirements and the use of measures 

to reduce drift will reduce exposure and risk.

Azadirachtin use in this program is not expected to cause adverse impacts 

to soil, water, or air quality. Degradation in soil appears to be microbially 

mediated, with a half-life of approximately 20 days at 25 °C (Stark and 

Walter, 1995). Persistence in water varies, with reported dissipation 

half-lives as short as a day up to 30 days (Thompson et al., 2004). 

Azadirachtin is not expected to bind strongly to soil and is very 

susceptible to photolysis with a half-life of less than 1 hour (Johnson and 

Dureja, 2002). Azadirachtin is not expected to volatilize into the 

atmosphere and would only occur as drift from ground or aerial 

applications. Photolytic instability and the use pattern in this program will 

minimize any potential off-site impacts to air quality. 

f. Bifenthrin (Citrus Groves)

(1) Human Health Toxicity and Risk

Bifenthrin is a synthetic pyrethroid insecticide with a mode of action 

similar to other pyrethroids, such as cyfluthrin, which was previously 

discussed. Bifenthrin has moderate acute oral toxicity but low dermal 

toxicity. It is not considered to be a dermal sensitizer or an eye or skin 
30

irritant (EPA, 2007a). Bifenthrin is not considered to be a reproductive or 

developmental toxicant. However, it is considered a potential carcinogen 

based on the formation of urinary bladder tumors when administered at 

high doses to mice. 

The application of this insecticide is limited to treatments of citrus groves. 

The potential for bifenthrin exposure would be restricted to applicators 

and no adverse effects are expected with adherence to label requirements 

and other standard operating procedures. Ground and surface drinking 

water resources are not expected to be impacted based on label restrictions 

regarding the protection of surface water and the environmental fate 

properties for bifenthrin which demonstrate low solubility and a high 

affinity for binding to soil. Risks to the general population that would 

consume treated citrus from orchards that received foliar applications of 

insecticides would be low due to the short persistence of bifenthrin in the

environment, and the timing of application relative to harvest which would 

allow for significant degradation.

(2) Nontarget Toxicity and Risk

Bifenthrin has low to slight toxicity to birds and moderate acute toxicity to 

wild mammals. Significant exposure and risk to nontarget terrestrial 

vertebrates is not expected due to low toxicity and low residue levels 

expected on plant and insect food items. Impacts to terrestrial 

invertebrates from bifenthrin treatments within the citrus groves are 

expected. Bifenthrin is considered highly toxic to honey bees by oral and 

contact exposure. 

Similar to other pyrethroid insecticides, bifenthrin is considered highly 

toxic to fish and aquatic invertebrates. Toxicity values for both groups of 

organisms ranges from the low parts per trillion (ppt) to the low parts per 

billion (ppb), depending on the test species and conditions (Solomon et al.,

2001; EPA, 2009). The greatest risk of exposure to aquatic resources is 

through drift from bifenthrin applications in citrus groves. Bifenthrin 

runoff is not expected to be a significant route of exposure to aquatic 

resources because this type of insecticide binds tightly to soil and has very 

low solubility, reducing the potential for transport and exposure to most 

aquatic organisms. 

Bifenthrin has extremely low solubility and mobility in soil, suggesting

that it would not be a threat to ground water. Threats to surface water 

quality would be primarily from drift which is reduced by the 

implementation of spray drift mitigation measures and any label-required 

application buffers from aquatic resources. Impacts to air are not expected 

because of the low vapor pressure for bifenthrin. 
31

g. Carbaryl (Residential/Citrus Groves)

(1) Human Health Toxicity and Risk

Carbaryl is a carbamate10 insecticide with a mode of action that occurs 

primarily through acetylcholinesterase (AChE) inhibition11

a foliar treatment against psyllids and other leaf-dwelling insects.

(Klaassen 

et al., 1986). Carbaryl is a broad-spectrum insecticide that is effective as 

The acute oral median lethal toxicity of carbaryl is considered to be 

moderate to mammals. Inhalation and acute dermal toxicity are 

considered to be low. The formulations of carbaryl that may be used in 

the program are of comparable or lower acute toxicity than the active 

ingredient. The program applications pose minimal dermal irritation and 

no dermal sensitization. The formulations that may be used in the 

program may result in mild eye irritation. Carbaryl is readily metabolized 

and largely excreted from humans within 24 hours. The primary 

metabolite of carbaryl, 1-naphthol, is considerably less toxic than the 

parent compound. 

The toxicity of carbaryl may be increased by exposure to some other 

carbamates and organophosphates (Knaak and O’Brien, 1960; Keplinger 

and Deichmann, 1967; Segal and Fedoroff, 1989). Although this is 

possible in the program area, it is unlikely that the timing of program 

applications of carbaryl will occur at an interval close enough to result in 

this effect on toxicity. 

A chronic feeding study of dogs determined a no observed effect level 

(NOEL)

12 of 3.83 milligrams per kilograms per day (mg/kg/day) for 

carbaryl based upon significant decreases in plasma and brain 

cholinesterase activity at higher doses (EPA, OPPTS, 1994). A 

subchronic rat neurotoxicity study found a NOEL of 1 mg/kg/day based 

upon decreased blood and brain cholinesterase13 at higher doses (EPA, 

2007b). Reproductive and developmental toxicity studies in rats found a 

maternal NOEL of 1 mg/kg/day and a teratologic14

 10 Carbamates are organic compounds derived from carbamic acid (NH2COOH).

NOEL of 3.15 

mg/kg/day. Carbaryl has been classified as a likely carcinogen based upon 

vascular tumors and hepatic and kidney adenomas (a type of benign 

tumor) found in a chronic carcinogenicity study. Chromosomal damage 

11 Inhibitors of acetylcholinesterase act by disrupting the transmission of nerve impulses across the 

nerve synapses in animals. Depending on the degree of acetylcholinesterase inhibition, effects can 

include anything from headaches, mental confusion, blurred vision, and muscle twitching to muscle 

paralysis. 12 The highest tested dose of a substance that has been reported to have no harmful health effects.

13 An enzyme that is widely distributed throughout the muscles, glands, and nerves of the body that 

converts acetylcholine into choline and acetic acid.

14 Causing malformations of an embryo or fetus.
32

has been reported with high doses of carbaryl, but no in vivo15 mutagenic 

effects have been observed (EPA, 2007b).

Carbaryl is applied as a foliar treatment in the program either to residential 

citrus or in citrus groves. Due to higher application rates, exposure was 

greater for applicators than other residential foliar treatments; however,

due to its low toxicity it was shown to have wide margins of safety 

(USDA–APHIS, 2008). 

Ingestion of contaminated drinking water and treated citrus fruit were 

exposure scenarios analyzed for the use of carbaryl. All calculated risks 

for children and adults indicate minimal risk to the public for residential 

applications (USDA–APHIS, 2008). 

(2) Nontarget Toxicity and Risk

The acute oral median lethal toxicity of carbaryl is considered to be 

moderate for mammals, while toxicity to birds ranges from toxic to 

practically nontoxic, with acute oral median lethal toxicity values from 

16 mg/kg to greater than 2,000 mg/kg. Exposures to carbaryl of mammals 

and birds from residential program applications were determined to result 

in doses that pose minimal acute or chronic risks (USDA–APHIS, 2008). 

Indirect impacts to insectivores16 (e.g., loss of terrestrial invertebrate prey)

are not expected to be of concern in residential applications. Any effects 

will be localized based on the method of application and the selective 

treatment of individual host trees. There is the potential for indirect 

impacts to birds and mammals that forage for terrestrial invertebrate prey 

items in carbaryl treated citrus groves. Carbaryl has a short half-life in the 

environment; therefore, recovery of nontarget terrestrial invertebrates 

would be expected to occur for most invertebrates.

The broad-spectrum activity of carbaryl results in high toxicity to most 

insects, including pollinators. The 48-hour contact median lethal dose for 

honey bees is 0.001 microgram per bee (μg/bee). Adherence to carbaryl 

label requirements regarding the protection of honey bees will reduce 

exposure and risk to honey bees and other pollinators.

Carbaryl is moderately to highly toxic to fish, and very highly toxic to all 

aquatic insects and to most aquatic crustaceans. Carbaryl is not subject to 

significant bioaccumulation17

 15 Experiments done in or on living tissue or a whole, living organism.

due to its low water solubility and lack of 

uptake in plant and animal tissues. Aquatic vertebrates and invertebrates 

may be exposed to carbaryl through runoff or drift adjacent to the site of 

application. Exposure to aquatic resources from residential applications is 

16 Species whose diet consists primarily of insects.

17 The accumulation of substances, such as pesticides, or other organic chemicals in an organism.
33

expected to be less than those from citrus grove applications. Applications 

in residential treatment areas are to individual trees using ground 

equipment, compared to broadcast aerial and ground applications in citrus 

orchards. Aquatic resources adjacent to citrus groves may receive 

exposure from carbaryl applications. Sensitive sites, such as shallow, 

static bodies of water, may be impacted by carbaryl applications. Risk is 

greatest for aquatic invertebrates because they are more sensitive to 

carbaryl, potentially resulting in indirect impacts to aquatic vertebrates 

that depend on these resources as prey. Exposure and risk to aquatic sites 

can be reduced by adherence to label requirements for each carbaryl 

formulation that may be used in either residential or citrus grove 

applications. 

Carbaryl is not expected to persist in the environment under the proposed 

use patterns. Carbaryl degrades rapidly in soil and water with half-lives in 

laboratory and field studies ranging from less than 1 day to approximately 

20 days (FS, 2008a). Carbaryl is not considered to be a threat to ground

water resources because it is not considered to be mobile and susceptible 

to leaching. Carbaryl could impact surface water quality in situations 

where aquatic resources are adjacent to treatment sites. Water quality 

impacts will be minimized by following adherence to label requirements 

for ground and aerial treatments. Carbaryl is not expected to have impacts 

to air quality from volatilization18 after application. Carbaryl will occur in 

the atmosphere during application as spray droplets; however, this will 

occur in the immediate area of application and will dissipate quickly after 

treatment. 

h. Chlorpyrifos (Citrus Groves)

(1) Human Health Toxicity and Risk

Chlorpyrifos is an organophosphate insecticide with a mode of action that

occurs primarily through the inhibition of cholinesterase enzyme. Signs 

and symptoms of low doses include localized effects (such as nosebleeds, 

blurred vision, and bronchial constriction) and systemic effects (such as 

nausea, sweating, dizziness, and muscular weakness). At higher doses, the

signs and symptoms include irregular heartbeat, elevated blood pressure, 

cramps, and convulsions. Acute oral toxicity is moderate based on median

lethality values ranging from 60 to 1,000 mg/kg, depending on the test

species. Dermal toxicity is considered low, and the formulated material 

can cause moderate eye and skin irritation. Chlorpyrifos is not considered 

mutagenic, teratogenic, or carcinogenic by EPA (USDA–APHIS, 2005b). 

The application of this pesticide would be limited to one application by 

either ground or air in areas that are established citrus groves. 

 18 The conversion of a chemical substance from a liquid or solid state to a gaseous or vapor state.
34

Contamination of ground water resources is not expected based on the 

environmental fate for chlorpyrifos. Application buffers and spray drift 

mitigation language on chlorpyrifos labels will reduce surface water 

contamination, and, based on the fate of chlorpyrifos in aquatic 

environments, any residues that may occur would be expected to partition 

to sediment. Exposure to the general population that may consume treated 

citrus from these types of applications would be low due to the timing of 

application relative to harvest, adherence to preharvest intervals, and the 

low levels of chlorpyrifos residues that may occur in edible portions of 

citrus (Iwata et al., 1983; Montemurro et al., 2002). 

(2) Nontarget Toxicity and Risk

Chlorpyrifos is considered to be moderately to highly toxic to birds, 

depending on the test species (EPA, 2009a; USDA–APHIS, 2005b).

Symptoms of nonfatal exposure to birds include cholinesterase depression 

(ChE), weight loss, reduced egg production, and reduced hatchling 

survival. There is the possibility of some direct impacts to wildlife that 

would forage exclusively on plant and insects within treated citrus groves. 

Risk is reduced for those wildlife species that may also forage outside 

treated groves. Indirect impacts to mammals and birds that depend on 

insects as part of their diet could occur for those species that forage 

exclusively in citrus groves. The ability of wild mammals and birds to 

forage in areas outside of the groves, as well as recovery of impacted 

invertebrates in treated groves, will reduce those types of potential impacts 

to wildlife populations. Impacts to terrestrial invertebrates, such as worker 

honey bees, are expected; however this effect would be restricted 

primarily to areas within and adjacent to citrus groves. Precautionary 

language prohibiting applications to blooming plants when bees are 

actively foraging would further reduce impacts to pollinators.

Chlorpyrifos is highly toxic to fish and aquatic invertebrates with acute 

median lethality values ranging from the low ppt to low ppb range, 

depending on the test species (EPA, 2009a; USDA–APHIS, 2005b). 

Exposure and risk to aquatic species would be reduced by adherence to

label requirements to reduce drift, and by applying buffers of 25 feet for 

ground applications and 150 feet for aerial applications from all aquatic 

resources.

Potential effects of chlorpyrifos on air, soil, or water quality would be 

restricted to areas near the site of application. Chlorpyrifos can persist in 

soil and water for several months under certain conditions; however, the 

persistence is generally only for a month or less. This is dependent on the 

organic content of the soil. Chlorpyrifos degrades quickly in the presence 

of light, with a half-life of approximately 2.7 hours. In water, it will bind 

readily with sediment with aqueous half-lives ranging from 7 to 28 days. 

Chlorpyrifos can volatilize into the atmosphere; however, its persistence is 
35

expected to be short, with a half-life of only a few hours because of its 

photolytic sensitivity (USDA–APHIS, 2005b). Chlorpyrifos can impact 

air quality through drift from ground or aerial applications. These impacts 

would be restricted to areas within established citrus groves with off-site 

transport reduced by strict adherence to label requirements regarding the 

minimization of drift.

i. Citrus Oils (Citrus Groves)

(1) Human Health Toxicity and Risk

Citrus oil is a biological insecticide derived from the extraction of oils 

from citrus that can be used to control certain insect pests. These oils are a 

proprietary mixture of different materials, with limonene being one of the 

components with insecticidal activity. Constituents of citrus oil have been 

shown to have low mammalian toxicity (EPA, 1994). Prolonged 

inhalation of mist or vapors of the formulated material can cause adverse 

effects, and contact with the eye can cause substantial irritation. 

Citrus oil use in this program would be as a foliar application in citrus 

groves. In citrus groves, exposure would be restricted to workers and 

applicators. Based on available toxicity data and the requirements for 

personal protective equipment, risk is expected to be minimal. Threats to 

ground or surface water resources are not expected based on the chemical 

fate of citrus oil which suggests low solubility and mobility.

(2) Nontarget Toxicity and Risk

Nontarget toxicity data for citrus oils is limited; however, data for some 

constituents contained within these types of materials, such as limonene, 

demonstrate that acute and subacute toxicity to birds is extremely low. 

The low toxicity to terrestrial vertebrates suggests minimal direct risk to 

wild mammals and birds. Indirect impacts through the loss of insect prey 

to this group of organisms are not expected because citrus oils are not 

considered broad-spectrum insecticides and would only have impacts to a 

small group of terrestrial invertebrates. Toxicity to terrestrial 

invertebrates, such as honey bees, is unknown. 

Aquatic toxicity is low, with median lethality values in the low-ppm range 

for invertebrates and fish, based on limited available data (Kassir, et al.,

1989; EPA, 1994). Exposure to aquatic habitats adjacent to citrus groves 

may occur during aerial applications, although adherence to label 

requirements, the environmental fate of these types of oils, and low 

toxicity suggest that adverse impacts would not be expected in these types 

of environments.
36

Citrus oil impacts to soil, water, and air quality are expected to be 

negligible. All treatments would be made in a manner to minimize off-site 

transport, thereby minimizing impacts to water quality. Impacts to ground 

water are not expected because citrus oil is not considered soluble or 

mobile. Citrus oil can occur in the atmosphere as drift from ground and 

aerial applications; however, this impact would be short in duration and 

occur primarily within the treatment block. 

j. β-Cyfluthrin (Residential/Citrus Groves)

(1) Human Health Toxicity and Risk

Cyfluthrin is a synthetic pyrethroid insecticide19 with broad-spectrum 

activity. The mode of toxic action occurs by causing the sodium channels 

to stimulate nerves to produce repetitive discharges. Muscle contractions 

are sustained until a block of the contractions occurs. Nerve paralysis can 

occur at high levels of exposure (Walker and Keith, 1992). Cyfluthrin is 

effective against psyllids and other sucking insects when applied as a 

foliar treatment. 

The acute oral median lethal toxicity of cyfluthrin is considered to be low 

to moderate in mammals. Inhalation and acute dermal toxicity are 

considered to be low. The formulation of cyfluthrin to be used in the 

program is of comparable or lower acute toxicity than the active 

ingredient. The program applications pose no evident dermal irritation or 

sensitization, but may result in mild eye irritation. An acute neurotoxicity 

study using the rat resulted in a decrease in motor activity at 10 mg/kg/day 

with a resulting NOEL of 2 mg/kg/day. Based on this study, the acute 

RfD was set at 0.02 mg/kg/day (EPA, 2005a). Cyfluthrin is rapidly 

absorbed and largely excreted as conjugated (joined) metabolites within 

48 hours. 

Synergism of the toxicity of organophosphates and synthetic pyrethroids,

such as cyfluthrin, has been shown in laboratory and field tests (Keil and 

Parrella, 1990; Horowitz et al., 1987). Although this is possible in the 

program area, it is unlikely that the timing of applications of 

organophosphates will occur at intervals close enough to program 

applications of cyfluthrin to result in this effect. 

Chronic studies of oral exposures were found to have a NOEL of 

2.5 mg/kg/day and a lowest observed effect level (LOEL)20

 19 Pyrethroids are synthetic chemical compounds similar to the natural chemical pyrethrins produced 

by the flowers of pyrethrums. 

of 

6.2 mg/kg/day based upon decreased body weights and other effects. 

Uncertainty factors were applied to the NOEL to determine the chronic 

20 LOEL is the lowest tested dose of a substance that has been reported to cause harmful health 

effects.
37

RfD for cyfluthrin of 0.025 mg/kg/day (EPA, 1997a). An acute RfD of 

0.02 mg/kg/day was determined based upon a rat neurotoxicity study 

(EPA, 2005a). Reproductive and developmental toxicity studies in rats 

found a maternal NOEL of 3 mg/kg/day, and a developmental NOEL of 

10 mg/kg/day. Cyfluthrin is not considered to pose mutagenic or 

carcinogenic risks (EPA, 1997a).

Cyfluthrin will be applied as a foliar treatment. The potential exposure to 

applicators was determined to be two to four orders of magnitude lower 

than the RfD, so there is minimal risk for workers (USDA–APHIS, 2008). 

Ingestion of contaminated drinking water and treated citrus fruit were 

exposure scenarios analyzed for the use of cyfluthrin. All calculated risks

for children and adults indicate minimal risk to the public (USDA–APHIS, 

2008). 

(2) Nontarget Toxicity and Risk

The acute oral median lethal toxicity of cyfluthrin is considered to be low 

to moderate for mammals. Inhalation and acute dermal toxicity are 

considered to be low. The formulation of cyfluthrin to be used in the 

program is of comparable or lower toxicity than the active ingredient. 

Cyfluthrin is considered to be practically nontoxic to birds with acute oral 

median lethal toxicity values greater than 2,000 mg/kg (EPA, 2010a). 

Exposure to nontarget terrestrial animals from residential treatments is 

expected to be lower because applications are made to individual trees, 

compared to citrus groves where broadcast applications over a larger area 

will occur. Residential treatments will only be made to individual citrus 

trees and not other vegetation present in these areas. 

Mammals and birds and other wildife that may forage for invertebrate 

prey will have other available food items from plants that have not been 

treated; treated citrus is expected to be recolonized by terrestrial 

invertebrates after treatment. The potential for indirect risk is greater in 

citrus orchards because applications are broadcast over groves which will 

occupy a larger area when compared to the residential treatments. Direct 

risk to wild mammals and birds that may feed on contaminated prey is 

expected to be low for both proposed use patterns (based on the available 

toxicity data) and conservative estimates of residues that can occur on 

prey items. There is the potential for indirect risk to terrestrial vertebrates 

that depend on insects as a food source. This type of risk is greater in 

citrus groves compared to residential treatments. Cyfluthrin is expected to 

impact some nontarget terrestrial invertebrates, resulting in a temporary 

depression in invertebrate populations in treated citrus groves. The 

potential for indirect impacts will be greater in larger groves due to the 

larger area of application relative to the foraging range for small mammals 

and birds; however, their ability to forage outside the range of the groves 
38

and the recovery of invertebrate populations will help to minimize the 

potential for these types of impacts. 

The broad-spectrum activity of cyfluthrin results in high toxicity to most 

insects, including pollinators. The 48-hour contact median lethal dose for 

honey bees is 0.037 μg/bee (EPA, 2010a). Adherence to cyfluthrin label 

requirements regarding the protection of honey bees will reduce exposure 

and risk to honey bees and other pollinators.

Cyfluthrin is highly toxic to fish and very highly toxic to most aquatic 

invertebrates (EPA, 2010a). The greatest risk to aquatic resources is 

through drift from cyfluthrin applications. Cyfluthrin runoff is not 

expected to be significant to aquatic resources because this type of 

insecticide binds tightly to soil and has very low solubility, thereby

reducing the potential for transport and exposure to most aquatic 

organisms. Drift from residential applications to aquatic areas is expected 

to be less than from applications to citrus groves. Residential applications 

are made to individual trees using hand-held spray equipment which helps 

to reduce potential drift. Larger broadcast applications to citrus groves 

will increase the chance of off-site transport from drift to aquatic 

resources. Adherence to label requirements for cyfluthrin formulations 

registered for use in citrus groves provide multiple measures to reduce the 

potential for drift from areas of application. Spray drift restrictions, as 

well as other measures such as buffer zones from aquatic sites, that are 

stated on the labels will reduce exposure and risk to aquatic organisms. 

Cyfluthrin impacts to soil, water, and air quality are expected to be 

minimal based on the environmental fate and label requirements for 

application. Cyfluthrin half-lives in soil are variable depending on pH and 

organic matter. Laboratory and field dissipation half-lives range from 

approximately 30 to 94 days. Once cyfluthrin reaches the soil, it binds 

very tightly to soil particles and is not considered to be water soluble. The 

high affinity for soil and low solubility suggest that any cyfluthrin that 

reaches an aquatic resource will be soil bound or partition very rapidly to 

the sediment. The lack of mobility suggests that ground water 

contamination will not be a concern. Surface water quality could be 

impacted from drift during applications; however, several mitigation 

measures are stated on the label to protect surface water quality. 

Cyfluthrin will only occur in the atmosphere during application; however, 

it will dissipate rapidly and is not expected to volatilize back into the 

atmosphere, based on its chemical properties. 
39

k. Deltamethrin (Citrus Groves)

(1) Human Health Toxicity and Risk

Deltamethrin is a pyrethroid insecticide that has both contact and ingestion 

activity to several pest insects. It is widely used on a variety of crops and 

ornamentals to control sucking insects, as well as some lepidopteran21

pests. 

Based on the test conditions and species, acute mammalian toxicity for 

deltamethrin is variable, with oral toxicity values ranging from toxic to 

practically nontoxic (CA DPR, 2000; Barlow et al., 2001). Dermal 

toxicity is considered to be low, as is the inhalation toxicity for most 

formulations, with the exception of one emulsifiable concentrate 

formulation which demonstrates moderate inhalation toxicity (CA DPR, 

2000). Several studies have shown that deltamethrin is not a carcinogen, 

mutagen, or teratogen (Barlow et al., 2001; EPA, 2004c). 

The potential for exposure to deltamethrin would be restricted to 

applicators during application; however, by adhering to label requirements 

and other standard operating procedures, no adverse effects to applicators 

are expected. The environmental fate of deltamethrin, as well as 

adherence to label requirements regarding applications near surface water, 

suggest that ground and surface drinking water resources would not be 

impacted. Deltamethrin exhibits a strong binding affinity to soil and 

sediment and has low water solubility, suggesting that it would not leach 

to ground water, and any surface water residues would partition rapidly to 

sediment. Risks to the general population that would consume treated 

citrus from orchards that received foliar applications would be low due to 

the relatively short half-life of deltamethrin in the environment and the 

timing of application relative to harvest.

(2) Nontarget Toxicity and Risk

Deltamethrin toxicity to nontarget birds and mammals suggests effects at 

lower concentrations for mammals when compared to birds, where 

deltamethrin is considered practically nontoxic (EPA, 2008). Direct risk 

to birds and mammals is not expected based on conservative assumptions 

of exposure and available toxicity data. There is the possibility of indirect 

impacts through the loss of invertebrate prey after treatment. This type of 

impact is only expected to occur for those terrestrial vertebrates that rely 

exclusively on deltamethrin-sensitive invertebrates within treated groves. 

Other invertebrates that are more tolerant of deltamethrin, as well as 

recolonization of the area from areas outside the citrus groves, would help 

to minimize indirect impacts. Deltamethrin is considered highly toxic to 

 21 Large order of scaly-winged insects, including butterflies and moths.
40

honey bees. Adherence to label requirements will help to minimize 

exposure and risk to honey bees that may forage in citrus groves.

 

Deltamethrin is considered highly toxic to fish and aquatic invertebrates, 

with fish being less sensitive than aquatic invertebrates (EPA, 2008; 

Solomon et al., 2001). Acute fish toxicity values vary based on test 

species and conditions, but range from the mid-ppt to low-ppb range 

(EPA, 2008). Acute aquatic invertebrate toxicity is also dependent on the 

test species and condition, with toxicity values that range from low-ppt to 

the low-ppb range (EPA, 2008). Aquatic chronic toxicity is also high for 

fish and aquatic invertebrates, with no effect concentrations in the low-ppt 

range. Exposure to aquatic habitats adjacent to citrus groves could result 

in adverse impacts to these types of habitats. Adherence to label 

requirements regarding the minimization of drift and any other restrictions 

will reduce off-site transport to these areas and reduce risk. 

Deltamethrin has low solubility and a strong binding affinity for soil and 

sediment. In aquatic environments, deltamethrin is stable to degradation 

at a neutral pH, but will degrade quickly in more alkaline environments. 

Deltamethrin is susceptible to photolysis and microbial degradation in 

water and soil (Laskowski, 2002). Deltamethrin has a low vapor pressure 

and is not expected to have adverse impacts to air quality. 

l. Diflubenzuron (Citrus Groves)

(1) Human Health Toxicity and Risk

Diflubenzuron is an insecticide that inhibits chitin production in 

invertebrates, and has a variety of agricultural and nonagricultural uses. 

The technical active ingredient and proposed formulation exhibit low 

acute toxicity to mammals with oral, dermal, and inhalation median 

lethality values greater than the highest test concentration (FS, 2004; 

Chemtura, 2008). Diflubenzuron is not considered to be mutagenic, 

carcinogenic, or teratogenic based on available laboratory toxicity studies. 

However, a primary environmental metabolite of diflubenzuron, 4-

chloroaniline is considered a probable carcinogen. Based on available 

mammalian studies that measured sublethal effects, the most sensitive 

endpoint appears to be impacts to hemoglobin which is involved in 

oxygen transport in blood. Diflubenzuron causes the formation of 

excessive methoglobin which is unable to transport oxygen. 

Diflubenzuron use in this program is restricted to ground or aerial 

applications in commercial citrus groves where exposure would be 

greatest for applicators. The low acute and chronic toxicity of 

diflubenzuron and adherence to label requirements regarding protective 

personal equipment suggest that the risk to this segment of the population 

would be low. Diflubenzuron has low solubility and partitions to soil and 
41

sediment suggesting that it would not leach to ground water that may serve 

as a drinking water source. The low mammalian toxicity and 

environmental fate properties suggest risk to surface water used as a 

drinking water source would also be low based on labeled use of 

diflubenzuron. 

(2) Nontarget Toxicity and Risk

Diflubenzuron toxicity to wild mammals and birds is low based on 

available toxicity data (FS, 2004; USDA–APHIS, 2010c). Toxicity 

values, based on acute exposures in birds, demonstrate median toxicity 

lethality values greater than the highest test concentration, and no 

observable effect concentrations of 250 ppm or greater in chronic 

exposures (EPA, 1997b; Kubena, 1981; Kubena, 1982). Exposure to 

diflubenzuron residues from program applications on wild mammal and 

avian food items is not expected to result in adverse effects (USDA–

APHIS, 2010c). There is the potential for indirect effects to mammals and 

birds because of the loss of invertebrate prey items after diflubenzuron 

treatment in citrus orchards. Field studies evaluating these types of effects 

in wild mammals have shown some shifts in diet after treatment with 

diflubenzuron, although no impacts were noted to wild mammal 

populations (Seidel and Whitmore, 1995; FS, 2004). Similar studies of 

different songbirds in forested areas treated with diflubenzuron have noted 

shifts in their insect diet after treatment (Stribling and Smith, 1987; 

Sample et al., 1993; FS, 2004).

Laboratory and field studies assessing nontarget impacts to terrestrial 

invertebrates have demonstrated minimal to no impacts on most terrestrial 

invertebrates, including honey bees. Evaluation of impacts to honey bees 

in field studies, including those conducted in citrus groves, have 

demonstrated safety to bees when using diflubenzuron (Emmett and 

Archer, 1980; Atkins et al., 1976; Schroeder et al., 1980; Robinson, 1979). 

Field studies assessing the impact of diflubenzuron on other nontarget 

terrestrial invertebrates has shown minimal impacts in a range of 

diflubenzuron applications (Sample et al., 1993; Catangui et al., 1996; FS, 

2004). 

Diflubenzuron has low to moderate acute toxicity to fish with median 

lethal concentrations ranging from the low-ppm range to greater than 

600 ppm for some species (USDA–APHIS, 2010c). Sublethal and chronic 

toxicity is also considered to be low based on available data. 

Diflubenzuron is considered highly toxic to most aquatic invertebrates. 

Acute toxicity can range from below 1 ppb for some freshwater 

crustaceans to greater than 125 ppm for the most tolerant aquatic 

invertebrates species (USDA–APHIS, 2010c). Available data for 

metabolites of diflubenzuron in aquatic environments demonstrates equal 

or lower toxicity when compared to the parent material. Direct risk to 
42

aquatic vertebrates is not expected when considering conservative 

exposure estimates in shallow water bodies. There is the potential for 

direct toxicity of diflubenzuron to aquatic invertebrates in water bodies 

adjacent to commercial citrus groves. Depending on the aquatic resource 

and the level of exposure, aquatic invertebrate losses could result in 

indirect effects to organisms dependent on these resources as food; 

however, in some cases, recovery of invertebrate populations would make 

these types of effects temporary.

Diflubenzuron impacts to air quality are not expected beyond the period of 

application where off-site drift could occur. Diflubenzuron has chemical 

and physical properties that suggest it will not volatilize into the 

atmosphere after application (USDA–APHIS, 2010c). Diflubenzuron has 

very low water solubility and preferentially adheres to soil particles; 

therefore, it is not considered to be mobile and is not a threat to ground 

water resources. Diflubenzuron could impact surface water quality via 

drift and runoff at the time of application, although this will be reduced by 

adherence to label requirements. Diflubenzuron persistence in sediment 

and water is expected to be short with half-lives of less than 35 days. 

Half-lives in soil are similar to those in aquatic systems. Dissipation halflives in citrus and apple orchards report values of 68 to 78 days, 

respectively. 

 

m. Dimethoate (Citrus Groves)

(1) Human Health Toxicity and Risk

Dimethoate is a systemic organosphosphate insecticide whose primary 

mode of action is through inhibition of cholinesterase. Acute exposure 

through oral, dermal, and inhalation routes demonstrate moderate oral 

toxicity and low dermal and inhalation toxicity (EPA, 2006a). Dimethoate 

is considered a slight to moderate eye and skin irritant, and available data 

for the proposed formulation for use in this program suggests comparable 

acute toxicity. Similar to other organophosphate insecticides, the most 

sensitive endpoint in short- and long-term exposures to dimethoate and its 

associated metabolite, omethoate, is cholinesterase inhibition (EPA, 

2006a). Dimethoate is considered a possible human carcinogen based on 

the formation of lymph and spleen tumors in laboratory test animals. 

Dimethoate applications are limited to ground or aerial foliar treatments in

citrus groves. Dimethoate exposure and risk during application is 

restricted primarily to applicators. Adherence to label requirements 

regarding the use of personal protective equipment and other standard 

operating procedures will reduce exposure and risk to applicators. 

Exposure to the general population that would consume dimethoatetreated citrus from orchards that received applications would be low based 
43

on the timing of application relative to harvest, which would allow for 

significant degradation, and adherence to preharvest interval restrictions. 

(2) Nontarget Toxicity and Risk

Dimethoate has moderate acute toxicity to wild mammals, based on 

median lethality values of 120 and 420 mg/kg in the mouse and rat, 

respectively (EPA, 2006a). Mammalian dermal and inhalation toxicity is 

considered low for the technical and proposed formulation material. 

Sublethal and chronic toxicity endpoints demonstrate cholinesterase 

inhibition, based on NOELs of less than 1.0 mg/kg/day (EPA, 2006a). 

Dimethoate is considered highly toxic to birds with acute oral median 

lethality values ranging 5.4 mg/kg for the red-winged blackbird to 

63.5 mg/kg for the mallard (EPA, 2010a). Chronic toxicity to birds was 

measured in reproduction studies with multiple sublethal impacts at 

10.1 ppm (EPA, 2006a). Because of the potential for exposure to food 

items that terrestrial vertebrates may consume in treated citrus groves, 

there is a greater risk to avian species compared to wild mammals. Direct 

acute risk to mammals is not expected but conservative assumptions 

regarding exposure, as well as a more sensitive acute lethality value, 

indicate that there may be risks to birds. Sublethal impacts may occur 

from exposure to organophospate insecticides, such as dimethoate, that act 

to inhibit cholinesterase. Sublethal impacts, such as changes in nesting 

behavior and predator avoidance, can result in effects on reproduction and 

populations after exposure to organophospate and carbamate insecticides. 

The risks from these types of impacts will be reduced for those wild 

mammals and birds that do not feed exclusively in treated citrus groves, 

and for those chemicals that have short residual half-lives. Chronic 

exposure to contaminated plant material from program applications are not 

expected due to the short half-life on plant surfaces that ranges from 0.9 to 

16.3 days (EPA, 2006b; Antonious et al., 2007). Due to the broadspectrum nature of the organophosphate insecticides, nontarget terrestrial 

invertebrate impacts would be expected in citrus groves immediately after 

application. For those terrestrial vertebrates foraging for terrestrial 

invertebrates in citrus groves, the amount of prey items would decrease 

after treatment. Significant population impacts to wildlife are not 

expected to occur because not all invertebrates would be impacted, and 

there would be recovery of most invertebrates within the citrus grove. 

Toxicity to pollinators, such as the honey bee, is high in acute and contact 

toxicity studies from exposure to dimethoate. Toxicity has also been 

shown to be high to other terrestrial invertebrates, such as parasitic wasps 

(EPA, 2006a). Risk to honey bees is reduced to some extent by adherence 

to label requirements for dimethoate applications in citrus. Restrictions on 

dimethoate application during the daytime (when bees are most active or 

when citrus trees are blooming) will reduce the exposure of honey bees 

and other pollinators.
44

Dimethoate acute toxicity to fish is considered moderate, while toxicity to 

aquatic invertebrates ranges from moderate to very highly toxic (EPA, 

2006a). The primary metabolite, omethoate, is more acutely toxic to 

aquatic invertebrates than dimethoate; however, it appears to be similar in 

toxicity to dimethoate, based on acute fish and chronic aquatic 

invertebrate data. Chronic and sublethal impacts to fish and aquatic 

invertebrates range from the low to upper ppb with aquatic invertebrates 

being the more sensitive taxa. Dimethoate exposure to aquatic biota in 

shallow aquatic habitats could result in adverse impacts; however, risk is 

reduced by adherence to label requirements regarding the prevention of 

drift and runoff.

Dimethoate does not exhibit properties that indicate volatilization into the 

atmosphere. Air quality would be impacted at the time of application in 

the citrus grove due to spray applications, although this would be localized 

and of short duration. Under aerobic conditions, dimethoate breaks down 

rapidly with soil half-lives ranging from 2.0 to 3.7 days (EPA, 2006b). 

Dimethoate is mobile in soil, thus, it could move off-site via runoff or 

leaching. Adherence to label requirements and avoidance of applications 

to permeable soils or areas where a high water table is present will reduce 

the probability of off-site transport to ground and surface water. 

n. Fenpropathrin (Citrus Groves)

(1) Human Health Toxicity and Risk

Fenpropathrin is a synthetic pyrethroid insecticide which affects the 

nervous system. It is a moderate skin and eye irritant. Signs and 

symptoms can include muscle contractions, tremors, loss of muscle 

coordination, and nerve paralysis at moderate to high levels of exposure. 

Fenpropathrin is not considered carcinogenic by EPA (USDA–APHIS, 

2005b).

The application of this pesticide would be limited to ground or aerial foliar 

treatments within established citrus groves. The environmental fate of 

fenpropathrin, as well as adherence to label requirements regarding 

applications near surface water, suggests that ground and surface drinking 

water resources would not be impacted. Fenpropathrin binds strongly to 

soil and sediment and has low water solubility, suggesting that it would 

not leach to ground water, and any surface water residues would partition 

rapidly to sediment. Risks to the general population that would consume 

treated citrus in orchard applications would be low due to the short 

half-life of fenpropathrin in the environment and the timing of application 

relative to harvest which would allow for significant degradation. 
45

(2) Nontarget Toxicity and Risk

The program use of fenpropathrin is unlikely to impact most nontarget 

wildlife. The toxicity of fenpropathrin is moderate to mammals and has a 

slight oral toxicity to birds. Direct risk to terrestrial vertebrates is not 

expected due to the moderate toxicity of fenpropathrin and expected low 

exposure from ground or aerial applications. Terrestrial invertebrates

would be impacted in areas of treatment; however, these effects would be

restricted to treated areas within the citrus grove, and would be temporary 

due to the recolonization of invertebrates from untreated areas (USDA–

APHIS, 2005b). Impacts to honey bees would be reduced by adherence to 

label requirements for use.

Fenpropathrin is highly toxic to aquatic organisms with median lethality 

values ranging from the low ppt to low ppb range for fish and aquatic 

invertebrates. Exposure and risk to these habitats will be reduced with 

adherence to label requirements, as well as label requirements for 

application buffers of 25 feet for ground applications and 250 feet for 

aerial applications, which will minimize drift to adjacent bodies of water. 

Impacts to air, water, and soil from the proposed fenpropathrin 

applications are expected to be minimal because of its use pattern and 

environmental fate properties. Fenpropathrin is persistent in water at a 

neutral pH; however, it degrades more quickly at alkaline pH values and 

has a hydrolysis half-life of 14 days. Photolytic degradation in soil is 

much faster when compared to water with reported half-lives in water 

greater than a year and 14 days in soil. Potential mobility is low, based on 

low water solubility and a high binding affinity for soil, reducing the 

potential for runoff. Residues on treated vegetation are also of short 

persistence (USDA–APHIS, 2005b). 

o. Formetanate Hydrochloride (Citrus Groves)

(1) Human Health Toxicity and Risk

Formetanate hydrochloride (HCL) is a carbamate insecticide with a 

primary mode of action resulting in the inhibition of cholinesterase. 

Formetanate HCL is highly toxic to mammals when ingested but has 

moderate toxicity when inhaled and low dermal toxicity (EPA, 2007c). 

The formulated material is considered toxic from ingestion and inhalation 

but has a low dermal toxicity similar to the active ingredient. The 

formulated product is considered harmful to the eyes when exposure 

occurs and may be a skin sensitizer (Gowan, 2007). In acute and chronic 

studies, the most sensitive endpoint in most studies was cholinesterase 

inhibition. Formetanate HCL is not considered to be carcinogenic, 

teratogenic, or mutagenic in laboratory studies, and no immune- or 

endocrine-related impacts have been observed (EPA, 2007c).
46

Applications will be restricted to ground applications in commercial citrus 

groves. Workers and applicators will be the population segment at 

greatest risk of exposure to formetanate HCL applications. Precautionary 

label language and personal protective equipment requirements will 

reduce exposure and risk to this group of the population. Formetanate 

HCL is considered to be highly water soluble so there is the potential for 

surface water contamination from runoff after treatment. Label language 

regarding the management of drift and runoff to water resources that may 

be used for drinking water will reduce exposure and risk to the general 

population. In addition, the rapid degradation of formetanate HCL in 

water, especially in neutral and alkaline conditions, will further reduce 

exposure in drinking water sources.

(2) Nontarget Toxicity and Risk

Formetanate HCL is highly toxic to wild mammals and birds based on 

surrogate laboratory toxicity testing. Oral median lethality values were 

typically below 50 mg/kg for both groups (EPA, 2003b). Toxicity to 

pollinators is low to moderate in acute laboratory and field residue studies. 

Other nontarget terrestrial invertebrates may be impacted within and 

adjacent to commercial citrus orchards when applications of formetanate 

HCL occur. These impacts will typically be confined to areas within the 

orchard, and effects to terrestrial invertebrates adjacent to the orchard will 

be reduced by making ground applications and adhering to spray drift 

language on the label designed to minimize insecticide movement to 

nontarget habitats.

Formetanate HCL toxicity to aquatic organisms is variable with cold and 

warm freshwater fish species having moderate toxicity (EPA, 2003b). 

Limited freshwater invertebrate toxicity data demonstrates high toxicity to 

freshwater cladocerans, and moderate toxicity to estuarine and marine 

aquatic invertebrates. Exposure and risk to aquatic organisms can be 

reduced by avoiding applications under conditions that would allow for 

runoff and adhering to label recommendations to reduce drift.

Formetanate HCL is not expected to persist in soil under aerobic or 

anerobic conditions. Laboratory and field studies that measured the 

degradation and dissipation of formetanate HCL reported half-lives 

ranging from approximately 6 to 30 days. Formetanate HCL is extremely 

water soluble and does not adhere to soil and sediment suggesting it could 

impact water quality in aquatic sites adjacent to commercial citrus 

orchards where applications would occur. Precautionary label language,

as well as avoiding applications to soils that are poorly drained, sloping 

towards aquatic areas, or where there is a high water table will reduce the 

potential for contamination. 
47

p. Imidacloprid/Cyflythrin (Citrus Groves)

(1) Human Health Toxicity and Risk

Imidacloprid is a systemic, chloro-nicotinyl insecticide whose mode of 

toxic action and toxicity has been described in section V.B.2.c., above. 

Cyfluthrin is a synthetic pyrethroid insecticide that affects the sodium 

channels which are responsible for nerve stimulation. Cyfluthrin is not 

considered to be an eye irritant or skin sensitizer. At moderate to high 

levels of exposure, signs and symptoms can include muscle contractions, 

tremors, loss of muscular coordination, and nerve paralysis. Cyfluthrin is 

not considered to be carcinogenic, mutagenic, or teratogenic by EPA. The 

difference in the mechanism of toxic action ensures that this mixture does 

not pose increased toxicity through synergistic action. Although 

synergistic effects on toxicity are possible with simultaneous exposure to 

organophosphates (such as chlorpyrifos) and cyfluthrin, this type of 

combined exposure is unlikely with the safety precautions required of this 

program and the lack of concurrent applications expected using 

organophosphate and pyrethroid insecticides. The application of this 

insecticide mixture is limited to a ground or aerial foliar treatment in 

production citrus groves. None of the routine or extreme exposure 

scenarios from this mixture pose unacceptable risks to workers or 

applicators. Moreover, required protective gear and safety precautions 

further ensure that no adverse effects to program workers are expected.

Imidacloprid applied with cyfluthrin is not expected to impact ground 

water resources. Adherence to label requirements (such as application

buffers and drift mitigation requirements) will reduce the possibility of 

surface water residues for either insecticide. In addition, cyfluthrin is 

expected to bind tightly with soil or sediment, and would only occur in 

surface water for a very short duration. The low mobility and solubility of 

cyfluthrin suggest it would not leach into ground water. Imidacloprid is 

considered to be more mobile and soluble; however, avoiding applications 

to soils where leaching is more likely, as well as areas where there is a 

high water table, will reduce the potential for ground water contamination. 

Risks to the general population that would consume treated citrus from 

commercial groves that received applications of insecticides would be low 

due to the timing of application relative to harvest, which would allow for 

significant degradation of the insecticides. 

(2) Nontarget Toxicity and Risk

Direct risk to wild mammals and birds from foliar applications of 

cyfluthrin and imidacloprid is not expected, based on available effects data 

and conservative assumptions of exposure. However, there is the 

possibility of indirect impacts to wildlife from the loss of invertebrate food 

items that would be affected by the insecticide treatment. Adherence to 
48

label requirements regarding treatment in areas when bees are actively 

foraging, or when blooms are present, will reduce exposure and risk to 

pollinators. 

This mixture is considered highly toxic to fish and most aquatic 

organisms, based on previous discussions regarding the individual use of 

each insecticide. Adherence to label requirements to reduce drift, as well 

as application buffers of 25 feet for ground applications and 150 feet for 

aerial applications from all aquatic resources, will reduce exposure and 

risk to aquatic vertebrates and invertebrates.

q. Kaolin Clay (Citrus Groves)

(1) Human Health Toxicity and Risk

Kaolin is a naturally occurring aluminosilicate material that has a nontoxic 

mode of action by acting as a repellant or by providing a protective barrier 

from insects and disease. In addition to its use for insect and disease 

control, kaolin is widely used in health products and toiletries, and as an 

indirect food additive (EPA, 2000). 

Based on available toxicity data, kaolin has low acute toxicity via oral, 

dermal, and inhalation routes. Kaolin is a minor eye irritant and is not 

considered a dermal irritant. The formulated product proposed for use in 

this program, which is a dust, may cause irritation to the throat, eye, and 

skin to workers; however, adherence to the label requirements and 

recommended personal protective equipment would reduce exposure. Due 

to the low toxicity of kaolin and similar clays, little chronic toxicity data 

exists. Some impacts to lung function, called kaolinosis, can occur in 

long-term exposure to kaolin particles; however, this would not be 

expected in this program because the material is not applied as a dust 

(WHO, 2005). 

Kaolin is proposed for use in commercial citrus groves where exposure 

would be greatest for workers and applicators. Based on the low toxicity 

of kaolin, its prevalence in the environment, and its low solubility, it is not 

expected to be a significant risk to ground or ground water resources. 

(2) Nontarget Toxicity and Risk

Available toxicity data for kaolin and other clay materials suggest low 

toxicity to nontarget terrestrial vertebrates. Toxicity to terrestrial 

invertebrates, such as pollinators, is also considered low, based on 

available data where acute median lethality values were greater than the 

highest concentration tested (EPA, 2000). Based on the low toxicity of 

kaolin clay and its repellent activity to some terrestrial invertebrates, direct 

and indirect effects to wild mammal and bird populations are not expected.
49

Available toxicity data for related clay materials to nontarget aquatic 

organisms demonstrate very low toxicity to aquatic invertebrates and 

vertebrates, with toxicity values typically above 100 ppm (WHO, 2005). 

Exposure and risk to nontarget organisms are expected to be minimal,

based on the low toxicity of kaolin and expected aquatic residues that 

could occur near citrus groves where applications may occur.

Kaolin use in this program is not expected to cause adverse impacts to 

soil, water, or air. Impacts to soil are not expected. In addition, 

significant volatilization or drift is not expected into the atmosphere, based 

on the physical properties of kaolin once it is mixed and applied to the 

foliage of host plants.

r. Malathion (Citrus Groves)

(1) Human Health Toxicity and Risk

Malathion is a broad-spectrum organophospate insecticide that when 

metabolized to malaoxon can inhibit cholinesterase. Acute exposure 

through oral, inhalation, and dermal routes demonstrates low toxicity to 

mammals (FS, 2008b). In most cases, median lethality values are greater 

than the highest test concentration, or are at levels that would not be 

expected to occur in actual application scenarios. It is considered a slight 

eye and skin irritant but is not a skin sensitizer (EPA, 2009b). In acute 

and chronic studies, the more sensitive endpoint tends to be cholinesterase 

inhibition. Malathion is not considered to be a mammalian reproductive 

or a teratogenic insecticide; however, there is information that suggests 

carcinogenicity is possible (EPA, 2009b). Other studies have shown 

enhancement or suppression of different immune functions in various 

studies over a range of doses (FS, 2008b). Recent studies also have 

suggested a link between attention deficit hyperactivity disorder (ADHD) 

and exposure to metabolic degradates of certain organosphophate 

insecticides (including malathion) that may occur on certain fruits and 

vegetables (Bouchard et al., 2010). While no residue levels are anticipated 

to exceed EPA tolerance levels, the presence of any residues would be 

mitigated because citrus fruits are typically washed and disinfected with 

sodium hypochlorite, sodium orthophenyl-phenate (SOPP), or peracetic 

acid (PAA), brushed, rinsed, and waxed prior to packing. Fruits entering 

processing facilities also are washed with disinfectants. 

The application of malathion is limited to ground or aerial treatments in 

commercial citrus groves. The potential for malathion exposure and risk 

during application would be restricted primarily to applicators. Current 

and recently proposed labeling to protect applicators, as well as adherence 

to other standard operating procedures, make it unlikely that the use of 

malathion would result in adverse impacts to applicators. Malathion does 

exhibit some properties that suggest it could move to ground water. 
50

EPA’s ground water database reveals that approximately 1 percent of 

wells sampled over a 20-year period had detectable levels of malathion 

(EPA, 2009b). Malathion, as well as the more toxic metabolite, malaoxon, 

has a very short half-life in water, suggesting that occurrence in either 

ground or surface water would be short lived. Implementation of label 

requirements designed to protect ground and surface water will reduce the 

risk to these resources. Risks to the general population that would 

consume treated citrus from orchards that have received applications 

would be very low due to the short persistence of malathion in the 

environment, the timing of application relative to harvest (which would 

allow for significant degradation), and adherence to preharvest interval 

restrictions. 

(2) Nontarget Toxicity and Risk

Malathion is slightly to moderately toxic to mammals and birds in acute 

oral exposure studies. Cholinesterase inhibition appears to be the most 

sensitive endpoint for measuring exposure in mammals and birds. 

Significant inhibition of cholinesterase by organophosphate insecticides

can lead to several sublethal impacts in exposed terrestrial organisms. 

Malathion is considered moderately to highly toxic to a wide range of 

terrestrial invertebrates. The range of contact median lethality values in 

honey bees ranges from 0.20 to 0.70 μg/bee. The alkali and alfalfa 

leafcutter bee appear to be similar in sensitivity with contact median 

lethality values of 0.31 and 0.47 μg/bee, respectively (FS, 2008b). Citrus 

groves treated with malathion would be expected to see some reductions 

in terrestrial invertebrates. The residual activity of malathion is short; 

therefore, invertebrates outside of the groves would be expected to move 

back into treated areas and reestablish populations. These reductions in 

invertebrate populations could lead to indirect impacts to wild mammals 

and birds that depend on these items as a food source. 

Malathion toxicity to fish ranges from highly toxic with a median lethality 

value of 4 ppb to greater than 15 parts per million (ppm) for the bonytail 

chub (USDA–APHIS, 2010c). Sublethal acute and chronic effects to fish 

have been noted in the low-ppb range based on cholinesterase inhibition 

and behavioral effects. Malathion is also considered highly toxic to 

aquatic invertebrates with median lethality toxicity values ranging from 

less than 1 ppb to greater than 100 ppm, depending on the test species. 

Direct risk to fish and aquatic invertebrates could occur in sensitive 

aquatic habitats that are adjacent to citrus groves. Indirect impacts to fish 

through the loss of invertebrate prey could occur in aquatic habitats where 

direct impacts to fish and amphibians would not be anticipated. Field 

studies designed to assess these types of impacts have observed indirect 

impacts in aquatic systems that were treated with multiple applications of 

malathion over time (Relyea and Dieks, 2008; FS, 2008b). 
51

Malathion impacts to air quality will be limited to citrus groves and 

adjacent areas during the time of application. Malathion is not expected to 

volatilize from terrestrial or aquatic environments based on chemical and 

physical properties (USDA–APHIS 2010c). Impacts to soil and associated 

microorganisms would only be expected to occur in the areas of treatment, 

and would be short lived based on the environmental fate properties of 

malathion. Persistence of malathion and its metabolite malaoxon in soil is 

expected to be short with half-lives generally less than a week. Malathion 

degradation in water is also short with half-lives in natural water bodies 

ranging from less than a day to approximately 10 days. The short half-life 

of malathion and its ability to bind to organic matter suggest that leaching 

to ground water is not expected. Surface water contamination can occur 

via drift and runoff. Adherence to label requirements regarding the 

protection of surface water will reduce potential residues for surface water 

adjacent to citrus groves.

s. Petroleum Oils (Citrus Groves)

(1) Human Health Toxicity and Risk

Petroleum oils are a blend of hydrocarbons that may be mixed with other 

pesticides, or can be used alone, to control some insect pests. Acute oral, 

dermal, and inhalation toxicity is very low for mammals; subchronic and 

chronic studies have also demonstrated low toxicity (EPA, 2007d). 

Petroleum oils can cause mild eye, skin, and throat irritation under 

prolonged exposure. Components of these oils have not been shown to be 

mutagenic or reproductive toxicants. Carcinogenicity has not been 

established based on a lack of conclusive evidence in experimental 

animals (EPA, 2007d).

Petroleum oils are proposed for ground or aerial application in commercial 

citrus groves. The greatest potential for exposure is to workers and 

applicators during application. Ground and surface water resources that 

could be used for drinking water are not expected to be significantly 

impacted due to the properties of petroleum oils which suggest low 

mobility, solubility, and binding affinity to soil and sediment (EPA, 

2007d). 

(2) Nontarget Toxicity and Risk

The acute effects of hydrocarbon solvents, including mineral oils and 

aliphatic or open-chained petroleum hydrocarbons, indicate low 

mammalian toxicity from ingestion, inhalation, or dermal exposures 

(Ebbon, 2000; EPA, 2007d). Chronic studies also indicate low toxicity to 

mammals based on several studies. Avian toxicity data is limited, 

although oral toxicity studies and dietary studies indicate that oils are 

considered practically nontoxic to birds (EPA, 2007d). There is the 
52

potential for impacts to eggs when direct treatment to bird nests occurs 

within citrus groves. Adverse impacts to wild mammals and birds are not 

expected based on conservative assumptions regarding petroleum oil 

concentrations on food items for wild mammals and birds, and the 

available toxicity data. Indirect effects through the reduction in 

invertebrate prey items could occur for those vertebrates foraging in the 

groves, although the impacts are expected to be less than with 

conventional insecticide use. Dilling et al. (2009) observed a reduction in 

the abundance of insects collected from eastern hemlock sites treated with 

horticultural petroleum oils compared to controls; however, no effects in 

species richness were observed. 

Available aquatic toxicity data indicate that the toxicity of oils is low for 

aquatic organisms and would only occur above solubility limits (Ebbon, 

2000). Median lethality values and no observable effect concentrations

for fish and aquatic invertebrates exposed to various mineral oils were 

well above 100 ppm. EPA (2007d) reported low toxicity to fish, although 

for two oils freshwater crustacean effects were reported at approximately 

1.0 mg/L. Impacts to aquatic invertebrates could occur in situations where 

they become trapped at the surface of bodies of water where oil has 

formed a layer. This would only occur in static bodies of water where 

wave action would not break up the layer of oil, and with significant drift 

during application. 

Petroleum oils will occur in the atmosphere during the time of application; 

however, they will dissipate quickly and are not expected to volatilize 

once they reach the site of application. Based on low solubility and 

adherence to soil particles, threats to ground and surface water are not 

expected. 

t. Phosmet (Citrus Groves)

(1) Human Health Toxicity and Risk

Phosmet is a broad-spectrum organophosphate insecticide that is 

registered for use to control several pests in agricultural and 

nonagricultural applications. Acute oral mammalian toxicity to the 

technical material is considered moderate with an oral median lethality 

value of 113 mg/kg. Inhalation and dermal toxicity is comparatively 

lower with median lethality values greater than the highest test 

concentration for the technical and formulated material (EPA, 2006c;

Gowan, 2007). Phosmet is not considered to be a skin irritant but can 

cause mild eye irritation. As with other organophosphate insecticides, the 

most sensitive endpoint in short- and long-term exposures is 

cholinesterase inhibition. Phosmet is not considered mutagenic, and 

carcinogenicity has not been shown in rat studies; however, in a study 
53

using mice, there was an increase in liver tumors in males and mammary 

tumors in females (EPA, 2006c). 

Phosmet applications will only occur in commercial citrus groves using 

ground or aerial equipment. Workers and applicators are the population 

segment that has the greatest potential for exposure and risk. Adherence 

to proposed mitigation measures for occupational exposures will reduce 

the risk to this population group (EPA, 2006c). Threats to drinking water 

resources will be minimized by adherence to label requirements regarding 

spray drift management to reduce surface water exposure, and avoiding 

applications to permeable soils or in areas where a high water table is 

present which could increase the likelihood of ground water 

contamination. 

(2) Nontarget Toxicity and Risk

Phosmet has moderate acute toxicity to mammals for both the technical 

and formulated material. Dermal toxicity is low; the inhalation median 

toxicity is higher than the highest test concentrations reported in studies 

for the technical and formulated material. Sublethal and chronic toxicity 

effect thresholds are based primarily on the inhibition of cholinesterase in 

various test organisms (EPA, 2006c). Phosmet acute toxicity to birds 

varies with acute median lethality values ranging from 18 mg/kg in the 

red-winged blackbird to 1,830 mg/kg for the mallard. Reproductive 

impacts have been noted in chronic phosmet exposure to birds at 

concentrations greater than 60 ppm (EPA, 2010a). Direct risk to wild 

mammals and birds that may consume contaminated food items in citrus 

groves is expected to be low when factoring availability of food items 

outside of citrus groves where phosmet applications have not occurred. 

Indirect impacts to mammals and birds that depend on terrestrial 

invertebrates will also be minimized by foraging in areas where treatments 

have not occurred, as well as recovery of nontarget invertebrates in areas 

of treatment. Impacts to terrestrial invertebrates are expected in treatment 

areas because of the broad spectrum of activity of the organophosphate 

class of insecticides. Acute contact and residue studies indicate that 

phosmet is considered highly toxic to honey bees (EPA, 2010a). 

Adherence to label requirements regarding the protection of honey bees 

will reduce exposure and reduce adverse impacts.

Phosmet acute median toxicity values for fish are variable depending on 

species, ranging from the low ppb for the coldwater species, rainbow trout, 

to the low ppm for the fathead minnow (EPA, 2010a). Phosmet is highly 

toxic to most aquatic invertebrates with acute median lethality or effect 

values ranging from approximately 2 ppb for aquatic crustaceans to 

greater than 90 ppm for mollusks. Phosmet exposure and risk to aquatic 

biota in habitats adjacent to treated citrus groves may occur, although 
54

adherence to label requirements designed to reduce the potential for 

off-site drift and run-off will reduce risk. 

Phosmet is not expected to have adverse impacts to air quality once 

applications are completed because it is not considered to be a volatile 

insecticide. Phosmet does not persist in soils, with half-lives of 3 days 

under aerobic conditions and 15 days under anaerobic conditions. 

Degradation in soil is microbially mediated (EPA, 2006c). In water, 

phosmet degradation is pH dependent. Half-lives range from 9 days at a 

pH of 5 to 16 hours at more alkaline conditions. Phosmet and its primary 

metabolite, phosmet oxon, demonstrate properties that could result in 

leaching to ground water or runoff into surface water. The likelihood of 

this type of transport is reduced by its rapid degradation in soil and 

avoidance of applications to sites that could result in off-site movement in 

water.

u. Pyrethrin (Residential/Citrus Groves)

(1) Human Health Toxicity and Risk

Pyrethrins are naturally derived extracts from certain species of 

chrysanthemum plants that have insecticidal properties. The mode of 

toxic action occurs through effects on the sodium channels to stimulate 

nerves to produce repetitive discharges. This results in muscle 

contractions that are sustained until a block of the contractions occurs. 

Nerve paralysis can occur at high levels of exposure (Walker and Keith, 

1992). Pyrethrins have certain properties that serve to both intoxicate and 

repel certain insects. The control activity occurs through direct contact of 

the insecticide with the insect; therefore, thorough coverage of the host 

plants is important to the successful control of ACP. 

The acute oral toxicity of pyrethrin to mammals is considered to be low to 

moderate. Acute dermal and inhalation toxicity are low. The formulation 

of pyrethrin to be used in the program has comparable acute toxicity to the 

active ingredient. This formulation poses slight dermal irritation, some 

dermal sensitization, and eye irritation. These effects are avoided by the 

use of proper protective gear by pesticide applicators. An acute RfD of 

0.07 mg/kg/day was established based on uncertainty and safety factors 

applied to the results of an acute neurotoxicity study (EPA, 2006d). The 

primary metabolites and degradation products of pyrethrin are considered 

to be of lower toxicity than the parent compound (EPA, 2005b). Pyrethrin 

is rapidly metabolized by mammals through oxidation and/or conjugation 

before excretion.

Synergism of the toxicity of organophosphates when combined with 

pyrethroids (such as pyrethrin) has been shown in laboratory and field 

tests (Keil and Parrella, 1990; Horowitz et al., 1987). Although this is 
55

possible in the program area, it is unlikely that applications of 

organophosphates will be made to treatment sites at an interval close 

enough to program applications of pyrethrin to result in this effect. Tank 

mix applications of pyrethrin and organophosphate insecticides are not 

anticipated, and applications at intervals that would allow for residues of 

both chemistry classes to result in simultaneous exposure are not expected 

based on typical insecticide application intervals.

Chronic oral studies of the rat found a NOEL of 4.37 mg/kg/day which 

was used by EPA to derive the chronic RfD of 0.044 mg/kg/day (EPA, 

2006d). Developmental toxicity studies of rabbits demonstrate a maternal 

NOEL of 25 mg/kg/day. A reproductive study of rats indicates a 

reproductive NOEL of 196 mg/kg/day, and an offspring NOEL of 

6.4mg/kg/day, based on decreased pup weights. A neurotoxicity study in 

rats determined a NOEL of 20 mg/kg/day, based upon the occurrence of 

tremors in female rats at higher concentrations. Carcinogenicity studies of 

pyrethrin have equivocal data based upon a reported treatment-related 

increase in hepatocellular (liver cells) adenomas. Pyrethrin does not 

appear to be mutagenic or teratogenic, based upon available data (EPA, 

2005b).

In this program, pyrethrin is applied as a foliar treatment. The potential 

exposure to applicators was determined to be from one to three orders of 

magnitude lower than the reference dose, so there is minimal risk for 

workers (USDA–APHIS, 2008). 

Ingestion of contaminated drinking water and treated citrus fruit were 

exposure scenarios analyzed for the use of pyrethrin in residential 

applications. All potential risks for children and adults were determined to 

be negligible (USDA–APHIS, 2008). Risks to the general population that 

would consume treated citrus from orchards that received applications of 

this insecticide would be low due to the short half-life of pyrethrin and the 

timing of application relative to harvest. 

(2) Nontarget Toxicity and Risk 

The acute oral median lethal toxicity of pyrethrin is considered to be low 

for mammals and birds. Available data indicate that inhalation and acute 

dermal toxicity are also low. The formulation of pyrethrin to be used in 

the program is of comparable toxicity to the active ingredient. Exposures 

of mammals and birds to pyrethrin from residential applications are 

unlikely to pose any acute or chronic risks (USDA–APHIS, 2008). 

Indirect impacts to insectivores (i.e., loss of terrestrial invertebrate prey) 

are not expected to be of concern in residential applications because the 

effects will be localized based on the method of application and the 

selective treatment of individual host trees. Adverse effects from 

residential applications to terrestrial invertebrates on untreated trees are 
56

minimized by the lack of substantial drift of the large droplet size of the 

pesticide formulation applied to host plants. In situations where pyrethrin 

would be used over large areas in citrus groves, there is the potential for 

some terrestrial invertebrate impacts that could result in temporary 

reductions in prey items. Not all terrestrial invertebrates would be 

expected to be affected, and there would be rapid recovery of the more 

sensitive terrestrial invertebrates because of the short residual half-life of 

pyrethrin. 

The broad-spectrum activity of pyrethrin results in high toxicity to most 

insects, including pollinators. The 48-hour contact median lethal dose for 

honey bees is 0.022 μg/bee. Risk to pollinators in treated residential areas 

will be less than for comparable treatments in citrus groves. Treating 

individual trees in residential settings will reduce the potential for drift. In 

addition, other nontreated flowering vegetation would be available for 

pollinator foraging. Adherence to label requirements designed to reduce 

exposure to honey bees will reduce exposure and risk in treated groves. 

Pyrethrin is highly toxic to fish and to most aquatic invertebrates (EPA, 

2006d). The greatest risk to aquatic resources is through drift from 

pyrethrin applications in citrus groves. Pyrethrin runoff is not expected to 

be significant to aquatic resources because this type of insecticide binds 

tightly to soil and has very low solubility, reducing the potential for 

transport and exposure to most aquatic organisms. Drift from residential 

applications to aquatic areas is expected to be less than from applications 

to citrus groves. Residential applications are made to individual trees 

using hand-held spray equipment which helps to reduce potential drift. 

The use of pyrethrins in this program is not expected to have adverse 

impacts to soil, water, or air due to their environmental fate profile. Halflives in soil and water are very short thereby reducing the time for any 

potential impacts to soil and water quality. The half-life of pyrethrin in 

soil ranges from 3.2 to 10.5 days. Pyrethrins bind tightly to soil particles, 

reducing their bioavailability in terrestrial and aquatic systems. Pyrethrins 

are light sensitive and have a photolysis22 half-life of less than 4 hours. 

Pyrethrins have low water solubility and short half-lives of 14 to 17 hours 

in alkaline water. The low mobility and solubility for pyrethrin suggest 

that leaching into ground water resources is not expected. Impacts to air 

quality are also not expected, based on the chemical characteristics of 

pyrethrin that indicate low volatility. Pyrethrin could occur in the 

atmosphere as drift from ground and aerial applications; however, 

adherence to label requirements will minimize the potential for off-site 

drift. 

 22 Chemical decomposition induced by light or other radiant energy.
57

v. Spinetoram (Citrus Groves)

 

(1) Human Health Toxicity and Risk

Spinetoram is an analogue of the insecticide, spinosad, a fermentation 

byproduct of the bacterium Saccharopolyspora spinosa. The insecticide 

has low oral, inhalation, and dermal mammalian toxicity in acute 

exposures to the technical and formulated material proposed for use in this 

program (EPA, 2009c; Dow, 2008). The formulation (DelegateTM WG) is 

a slight eye irritant but is considered nonirritating to skin. Spinetoram is 

not mutagenic, carcinogenic, or neurotoxic to laboratory test mammals at 

relevant test concentrations (EPA, 2009c). Parental reproductive effects 

have been noted at doses above those expected from use in this program; 

however, no impacts have been noted in offspring, suggesting low 

developmental and reproductive toxicity. No developmental effects were

noted in studies conducted with the rat and rabbit. Immune effects 

were noted in multiple test species represented by aggregation of 

macrophages23 in the spleen, lymph node, thymus, and bone marrow. The 

lowest reported NOEL was 2.49 mg/kg/day in the dog in long-term 

chronic exposures (EPA, 2009c). 

Spinetoram is proposed for use in citrus groves to be applied by air or as a 

ground orchard application. Because use is limited to production orchard 

groves, the highest potential for exposure is to applicators. Adherence to 

recommendations for personal protective equipment and the favorable 

toxicity profile for spinetoram result in low a probability of adverse 

impacts to applicators. Exposure to the public from contaminated 

drinking water or drift at levels that could pose significant risk is not 

expected. Adherence to label requirements regarding best management 

practices to reduce off-site transport from drift will reduce the potential for 

exposure. In addition, spinetoram has low water solubility and 

preferentially binds to soil which would further reduce exposure via 

contaminated surface or ground water. 

(2) Nontarget Toxicity and Risk

Available toxicity data indicate that spinetoram has low acute and chronic 

toxicity to wild mammals and birds (EPA, 2010a). The risk of spinetoram 

treatments in citrus groves is expected to be low for wild mammals and 

birds that may feed on contaminated food items. Indirect risks to 

terrestrial wildlife from the loss of invertebrate prey items could occur for 

those species that only forage within commercial citrus groves and rely on 

spinetoram-susceptible terrestrial invertebrates. These types of impacts 

are not anticipated for most terrestrial vertebrates because they would 

typically forage inside and outside of the groves, and other terrestrial 

 23 Macrophages are large, white blood cells found primarily in the bloodstream and connective 

tissues that help the body to fight off infections by ingesting the disease-causing organisms.
58

invertebrates that are not sensitive to spinetoram would be available. 

Spinetoram is toxic to some terrestrial invertebrates, including the honey 

bee, and impacts are expected in citrus groves where treatments would 

occur. Adherence to label requirements regarding the protection of honey 

bees will minimize risk to that group of insects. 

Spinetoram and its associated metabolites are highly toxic to fish and 

aquatic invertebrates. Aquatic invertebrate toxicity values range from the 

upper ppt in chronic studies to low ppb in acute studies, while available 

fish toxicity data demonstrate toxicity values in the upper-ppb to low-ppm 

range (EPA, 2010a). Direct risk to aquatic invertebrates is expected for 

those aquatic resources immediately adjacent to commercial citrus groves. 

These impacts would also result in indirect risk to fish and other aquatic 

biota, such as amphibians, that depend on invertebrate prey items as a food 

source. Adherence to label requirements regarding the protection of 

aquatic resources from spray drift and runoff will reduce the risk to 

aquatic fauna present adjacent to commercial citrus groves.

Spinetoram has low water solubility and adheres to soil; therefore, its 

impact to surface water quality is expected to be minimized because of 

preferential binding to soil and sediment. Spinetoram mobility in soil is 

considered to be low because of its chemical and environmental fate 

properties and, thus, the risk of ground water contamination is also low. 

Degradation of spinetoram in soil under aerobic conditions varies with 

half-lives ranging from 3 to 31 days, while persistence in aquatic systems 

can be much greater with water and sediment half-lives ranging from 

approximately 100 days to greater than 1 year (EPA, 2010a). Spinetoram 

is not expected to impact air quality through volatilization because its 

known chemical properties indicate that it would only occur in the 

atmosphere during times of application.

w. Spirotetramat (Citrus Groves)

(1) Human Health Toxicity and Risk

Spirotetramat is a ketoenole insecticide that acts primarily by preventing 

lipid metabolism in certain invertebrates. Spirotetramat was registered for 

control of sucking insects, such as psyllids and whiteflies, as well as mites, 

on a variety of crops. Registration was recently cancelled due to a court 

case in which the U.S. District Court for the Southern District of 

New York vacated all registrations issued by EPA for pesticide products 

containing spirotetramat. The court decision was based on EPA’s failure 

to provide an opportunity for public comment on the applications for those 

registrations before they were granted (EPA, 2010a). Evaluation and 

approval of the registration by EPA in the future, and the use of section 18 

emergency use exemptions will be required before its use in the proposed 

ACP program. 
59

Spirotetramat has low toxicity to mammals via oral, dermal, and inhalation 

exposures. Reported acute toxicity values demonstrate that median 

lethality occurs at values greater than the highest test concentration used in 

the study (EPA, 2008a). The formulation proposed for use in this program 

is not considered a skin irritant; however, it is a mild eye irritant and a skin 

sensitizer. Spirotetramat is not considered mutagenic, carcinogenic, or 

neurotoxic; however, reproductive and developmental effects have been 

observed at high doses. Developmental effects were only seen at levels 

that were considered maternally toxic (EPA, 2008a; Bayer CropScience, 

2007). 

Spirotetramat is proposed for use in commercial citrus groves by ground 

or aerial application. The population segment at greatest risk of exposure 

to spirotetramat is workers and applicators. Spirotetramat does exhibit 

environmental fate properties, such as high solubility and weak soil 

binding, which could pose a threat to drinking water near areas of 

application. Adherence to label requirements regarding the protection of 

surface water and avoidance of applications to permeable soils will reduce 

the probability of spirotetramat movement to ground and surface water 

resources. 

(2) Nontarget Toxicity and Risk

Spirotetramat toxicity to mammals and birds is low based on available 

acute toxicity data required for pesticide registration (EPA, 2008a). 

Chronic toxicity is also low for mammals, although reproduction studies 

have shown a range of sublethal impacts to birds at all tested 

concentrations. Because acute exposure levels will be below effect 

thresholds, wild mammals and birds that are foraging in spirotetramattreated citrus groves are not expected to be directly impacted. Chronic 

risk to mammals is not expected; however, there is the potential for 

chronic risk to avian species based on estimated residues and available 

toxicity data. As with other insecticides proposed for use in this program, 

there is the possibility of indirect impacts for those wild mammals and 

birds that rely on insects present in citrus groves. Spirotetramat is 

expected to have some impacts to nontarget terrestrial invertebrates, but 

most activity is against mites and sucking insects; therefore, other 

invertebrates that could serve as prey items would be available in citrus 

groves. Spirotetramat has low toxicity to honey bees, based on standard 

toxicity testing; however, other studies measuring sublethal brood impacts 

have observed effects below currently labeled rates (EPA, 2008a). 

Spiroteramat aquatic toxicity is variable depending on the test species and 

duration of testing. Toxicity to fish is considered moderate with median 

lethality values in the low-ppm range, while aquatic invertebrate toxicity 

studies demonstrate slight to high toxicity (EPA, 2008a). Based on the use 

rate for spirotetramat on citrus, the direct risk to fish is expected to be low. 
60

There is potential for some impacts to aquatic invertebrates; however, 

adherence to label restrictions regarding the protection of aquatic 

resources from drift and runoff will reduce the potential for significant 

impacts.

Aerial and ground applications of spirotetramat will result in the presence 

of material in the atmosphere immediately after application in and 

adjacent to the citrus groves. Adherence to label restrictions for 

application will reduce the potential for off-site impacts to air quality; 

significant volatilization into the atmosphere is not expected. Significant 

soil impacts are not anticipated based on the environmental fate profile for 

spirotetramat. Spirotetramat is not expected to persist in soils with halflives of a few days. Dissipation half-lives in soil and water are typically 

less than 3 days, with hydrolysis half-lives ranging from 8.6 to 47 days, 

depending on pH and temperature. Spirotetramat is water soluble and has 

low soil adsorption properties suggesting a potential for movement into 

ground water. Avoiding applications to permeable soils or areas where a 

high water table is present will reduce the threat to ground water. 

x. Thiamethoxam (Citrus Groves)

See section V.B.2.d. for information regarding thiamethoxam. 

y. Zeta-Cypermethrin (Citrus Groves)

(1) Human Health Toxicity and Risk

Zeta-cypermethrin is a synthetic pyrethroid insecticide that is used to 

control a variety of insect pests in agricultural and structural/residential 

uses. The active ingredient is a combination of eight isomers24 with 

four of the most insecticidally active isomers occurring at higher 

concentrations compared to cypermethrin. Formulated zeta-cypermethrin 

is moderately toxic via oral and inhalation routes of exposure to mammals,

but is considered to have low dermal toxicity. The formulated material is 

moderately irritating to the eyes and skin, however, it is not considered a 

skin sensitizer. Zeta-cypermethrin is not considered mutagenic or 

teratogenic; however, it is considered a possible carcinogen based on 

results from a chronic mouse study where benign lung tumors were 

observed at the highest dose level. These levels are well above those 

expected in this program. Similar effects were not observed in other test 

species in chronic studies (EPA, 2008b).

Exposure of the general public to zeta-cypermethrin during applications in 

this program is not expected because applications would occur within

 24 An isomer is a molecule with the same number of atoms as another but arranged into a different 

structure.
61

established citrus groves. Applications are not expected to impact 

drinking water supplies because zeta-cypermethrin has very low solubility 

and a high binding affinity for soil, indicating a low probability of vertical 

or lateral transport into ground or surface water.

Risks to the general population that would consume treated citrus from 

orchards that received applications would be low due to the timing of 

application relative to harvest which would allow for significant 

degradation and adherence to preharvest interval restrictions. 

(2) Nontarget Toxicity and Risk

Zeta-cypermethrin has low acute and chronic avian toxicity with reported 

acute median lethal doses and chronic no observable effect concentrations 

greater than the highest test concentration (EPA, 2005c). Toxicity is high 

to most terrestrial invertebrates, including honey bees, with label 

requirements regarding minimizing exposure in areas where bees are 

actively foraging. 

Estimates of residues on food items for wild mammals and birds in treated 

citrus groves would not be expected to cause direct adverse risk. There is 

the potential for indirect risk to wild mammals and birds from the loss of 

available invertebrate prey that would occur after treatment in citrus 

groves.

Zeta-cypermethrin is considered highly toxic to aquatic invertebrates and 

vertebrates with reported median lethality values in the low-ppt to low-ppb 

range, depending on the test species, although fish were slightly less 

sensitive when compared to aquatic invertebrates (Solomon et al., 2001; 

EPA, 2005c and 2008b). Impacts to aquatic biota would be expected for 

those resources near the citrus groves. Exposure would be reduced by 

adherence to label requirements, such as aerial and ground application 

buffers, drift mitigation language, and vegetative filter strips that are 

required for product use. 

Zeta-cypermethrin is not expected to cause adverse impacts to soil, water, 

or air quality because of the mitigation measures proposed on the label, as 

well as environmental fate and chemical properties. Zeta-cypermethrin 

breaks down in soil under aerobic and anaerobic conditions with half-lives 

of less than 65 days. Zeta-cypermerthrin has very low water solubility and 

a high binding affinity to soil and sediment that would result in a low 

probability of ground water contamination. Adherence to label restrictions 

regarding applications near water, and its physical and chemical properties 

would reduce impacts to surface water quality. Physical and chemical 

characteristics for zeta-cypermethrin preclude significant volatilization 

into the atmosphere. Zeta-cypermethrin may be present in the air as drift 

following ground and aerial applications, although strict adherence to label 
62

requirements, including spray drift precautionary language, will minimize 

off-site drift.

The APHIS–PPQ Pest Permitting Branch (PPB) has authority to regulate 

importation and interstate movement of biological control organisms. 

Before approving environmental releases of non-indigenous biological 

control organisms into the United States, PPB considers the impact on the 

environment, agriculture, threatened and endangered species, and other 

nontarget species. To date, PPB has only considered one biological 

control agent for ACP control. APHIS prepared an EA for the release of 

the parasitoid Tamarixia radiata (T. radiata) into the continental 

United States that resulted in a finding of no significant impact (USDA–

APHIS, 2010b). That document and finding is incorporated by reference 

into this EA. It describes the environmental impacts of the release of 

T. radiata into the environment of the continental United States. The 

cooperative ACP management and control program is proposing to 

incorporate biological control organisms of ACP as they are approved by 

PPB. T. radiata would be the first ACP biological control organism 

incorporated into the program.

An EA was prepared to analyze the environmental impacts of the interim 

rule prior to its implementation. This analysis resulted in the signing of a 

finding of no significant impact. Both of these documents are 

incorporated into this EA by reference. They may be found at 

http://www.aphis.usda.gov/plant_health/ea/downloads/citrusgreening-eaquarantine.pdf and 

http://www.aphis.usda.gov/plant_health/ea/downloads/citrusgreeningfonsi-quarantine.pdf. 

C. Cumulative Effects

Under NEPA, Federal agencies are required to analyze the potential 

cumulative impacts of a proposed action. The Council on Environmental 

Quality defines cumulative impacts as impacts on the environment that 

result from incremental impact(s) of an action when added to other past, 

present, and reasonably foreseeable future actions. Actions resulting in a 

cumulative impact may or may not be generated by the same agency. 

Cumulative impacts can result from individually minor but collectively 

significant actions taking place over a period of time.

 

All of the pesticides that would be used in the proposed program are 

registered for use on citrus by EPA. For commercial citrus producers, this 

means that any grower can legally use any one, or several, of the 

insecticides on their property at their discretion as long as they are used in 

accordance with the pesticide label. Most labels specify maximum 

allowable volumes, amount of active ingredient, and/or number of 

applications per year or cropping season which serves to restrict usage. 

3. Biological 

Control

4. Quarantine
63

The use of the insecticides in noncommercial settings is also subject to all 

restrictions on the pesticide label. In the case of the proposed cooperative 

ACP program, the applicators treating on commercial citrus properties 

would all be commercial citrus producers. Commercial producers are not 

obligated to participate in the program. Their participation is voluntary, 

therefore, they may or may not adhere to the recommendations of the 

program, depending upon what they determine is best for their operations. 

On the other hand, the applicators treating on noncommercial properties 

would all be State cooperators, or their designees, who would be bound to 

the recommendations of the program. 

In addition to the chemical treatments that would be utilized against ACP 

under the proposed action alternative, chemical treatments are currently 

required for use against ACP as part of USDA–APHIS’ June 17, 2010 

interim rule. As previously mentioned, this rule primarily regulates the 

interstate movement of nursery stock. Nursery stock that is to be moved 

interstate from an area quarantined for ACP must be treated with an EPAapproved insecticide that has also been approved for use by APHIS. The 

potential environmental impacts were analyzed in an EA in July, 2010 

(USDA–APHIS, 2009b). The EA stated that the only potentially affected 

areas to be treated pursuant to the proposed program were within 

commercial nurseries. As outlined in the July EA and the Environmental 

Consequences section of this EA, provided that persons applying the 

chemical treatments follow the pesticide label, its applicable directions, 

and all restrictions and precautions, including statements pertaining to 

Worker Protection Standards and buffer zones, the effects to the 

environment and to humans from chemical treatments within all ACPinfested areas (e.g., nurseries, dooryard treatments, and commercial 

groves) are not expected to be substantial. 

Citrus trees are susceptible to various pests in addition to ACP. Citrus 

growers currently treat their citrus trees with a variety of pesticides to kill 

or control these pests. For example, some major citrus diseases found 

within the affected environment are treated with EPA-approved 

fungicides—citrus canker, sooty mold, greasy spot, Alternaria brown spot, 

Phytophthora-induced diseases, melanose, citrus scab, and post-bloom 

fruit drop. Other citrus pests that require treatment include citrus tristeza 

virus and citrus blight. Of these citrus diseases, USDA–APHIS only 

regulates the treatment of citrus canker. Citrus canker, caused by the 

bacterium Xanthomonas citri subsp. Citri., has only been found in Florida. 

Under USDA–APHIS regulations, fruit moved from the citrus canker 

quarantine area must be treated with an EPA-approved disinfectant only at 

commercial packinghouses. The use of disinfectants is done within 

contained facilities so environmental effects would not be substantial. 

While USDA–APHIS may not require chemical treatment against the 

various other citrus pests, State agencies may require treatment or citrus 

growers may choose to treat their citrus trees. 
64

New citrus pests are always a threat, and chemical treatments may need to 

change to fit these needs. Citrus black spot is a citrus disease caused by a 

fungus (Guignardia citricarpa Kiely) and has been found at two sites 

within southern Florida. Sweet orange scab, a disease caused by a fungus 

(Elsinoe australis Bitanc. & Jenkins) has been confirmed as occurring at 

multiple sites in eastern Texas and one residential property in Orleans 

Parish, Louisiana. Other fungal diseases are present and routinely treated 

in each of the citrus-producing States. At this time, it is not known what 

changes, if any, may result from these recent finds. These diseases are 

controlled or suppressed effectively in other countries using many of the 

same fungicides currently applied to commercial citrus production in the 

United States. 

It is important to note that for every pest there is not necessarily another 

pesticide added to a citrus grower’s treatment plan. Under the proposed 

program, multiple pesticides could be utilized, which may prove beneficial 

to growers because it increases the ability of an applicator to find products 

that are registered to treat multiple citrus pests. APHIS’ participation in 

the proposed program could result, over time, in more efficient and 

effective uses of resources in a coordinated effort to control ACP and to 

protect trees from CG. Because there is no effective treatment for CG 

other than the destruction of the infected plants, the only logical way to 

protect citrus trees is to control the vector for CG. This means that control 

of ACP by commercial growers would occur. By assembling the 

country’s best expertise in control of citrus pests, sharing their advice with 

producers, and encouraging producers to cooperate in control efforts, a 

reduction in total pesticide applications for CG in commercial production 

areas may result over time. In the near term, however, as control efforts 

are initiated, there is likely to be an increase in total pesticide applications 

for ACP control. The extension of treatments to areas beyond commercial 

production sites would reduce populations of ACP in adjacent areas that 

can serve as reservoirs of ACP which could reinfest the commercial 

growing areas. 

Treatments in residential and other noncommercial production sites are 

likely to increase the total amount of insecticide used at these sites. The 

applications, however, would be done by highly qualified State 

cooperators, or their designees, and not by homeowners or other 

proprietors who are not proficient in pesticide applications. Therefore, the 

insecticide applications are likely to be done in the most efficient and 

effective manner. Plus, because they would be done as part of a larger, 

regional coordinated program, the probable result would be to reduce 

reservoirs of ACP that could reinfest commercial areas. 

In addition, allowing multiple pesticide classes to be used against ACP 

may reduce the probability of pesticide resistance. Pesticide resistance is a 

“heritable and significant decrease in the sensitivity of a pest population to 
65

a pesticide that is shown to reduce the field performance of pesticides” 

(EPA, 2001). An important pesticide resistance management strategy is to 

avoid the repeated use of a particular pesticide (EPA, 2001). By using 

various chemicals with different modes of actions, applicators might 

reduce the ability of ACP to develop pesticide resistance.

VI. Other Environmental Considerations

A. Endangered Species

Section 7 of the Endangered Species Act and its implementing regulations 

require Federal agencies to ensure their actions are not likely to jeopardize 

the continued existence of threatened or endangered species or result in 

the destruction or adverse modification of critical habitat.

APHIS is preparing a biological assessment that considers the impact of 

the proposed program and other ACP-related activities on federally listed 

threatened and endangered species and designated critical habitat in the 

citrus-producing counties in California, Florida, Texas, Arizona, 

Louisiana, and Puerto Rico. Upon conclusion of the assessment, APHIS 

will determine if the program would affect listed species or their critical 

habitats. APHIS will then request concurrence with this determination 

from the U.S. Fish and Wildlife Service (FWS) and National Marine 

Fisheries Service (NMFS).

In the meantime, APHIS recognizes its obligations under the Endangered 

Species Act. APHIS is working with FWS and NMFS to ensure that any 

regional or local actions taken under the proposed action do not affect 

threatened and endangered species or their designated or proposed critical

habitats. If there is a possibility for adverse effects to listed species or 

critical habitat, the proposed action will not occur until APHIS has 

completed its work with FWS and NMFS, and has reached either a 

determination of no effect to listed species for the site or until these 

agencies have concurred with a may affect but not likely to adversely 

affect determination by APHIS. 

B. Executive Orders

Consistent with Executive Order (EO) 12898, “Federal Actions to Address 

Environmental Justice in Minority Populations and Low-Income 

Populations,” APHIS considered the potential for the proposed action to 

have any disproportionately high and adverse human health or 

environmental effects on any minority populations and low-income 
66

populations. Colonias25 and farm worker housing can be located within

the potential action area. Applications in residential areas are on a 

voluntary basis for all population subgroups where, if granted consent by 

the landowner, an application will be made to individual residential citrus 

trees. The proposed method of treatment, adherence to label language by 

applicators, and notification of residents prior to spraying will minimize 

exposure and risk to all population subgroups, including minority and 

low-income populations. In cases where insecticide applications are made 

to commercial citrus orchards, there is the potential for additional 

exposure to workers and applicators. Adherence to label language 

regarding the use of personal protective equipment and other label 

language designed to reduce exposure will also reduce the risk to 

applicators and workers who may belong to minority and low-income 

populations. 

Consistent with EO 13045, “Protection of Children from Environmental 

Health Risks and Safety Risks,” APHIS considered the potential for 

disproportionately high and adverse environmental health and safety risks 

to children resulting from the proposed action of making applications to 

residential citrus. The potential for exposure and disproportionate adverse 

risk to this segment of the population is expected to be low as only 

backpack applications to an individual residential host tree will be made,

thereby minimizing exposure to the public compared to broadcast 

applications. In addition, adherence to label language and notification to 

those residents regarding treatments and precautionary measures to reduce 

exposure will reduce the risk to children. Residential treatments are 

voluntary; when consent is granted, it is the responsibility and obligation 

of the program pesticide applicators to ensure that the general public is not 

in or around areas being treated. This will reduce exposure and risk of the 

general public, including children, which could occur during the 

application process. Commercial citrus applications that are made by 

private applicators are not expected to result in adverse impacts to children 

because this subgroup of the population would not be expected to be in a 

commercial grove during an application. Notification of the public and 

posting can also reduce the possibility of exposure, as well as compliance 

with any application restrictions near residential areas and schools for 

certain insecticides. Adherence to label directions for each insecticide will 

also reduce exposure of children to insecticides from harvested fruit, as 

well as protect drinking water resources. 

 25 The term "colonia" in Spanish means a community or neighborhood. The Office of the Texas 

Secretary of State defines a "colonia" as a residential area along the Texas-Mexico border that may 

lack some of the most basic living necessities, such as potable water and sewer systems, electricity, 

paved roads, and safe and sanitary housing.
67

C. National Historic Preservation Act of 1966

Consistent with the National Historic Preservation Act of 1966, APHIS 

has examined the proposed action in light of its impacts to national 

historic properties. APHIS has determined that the proposed action is a 

type of activity that is unlikely to have the potential to cause effects on 

historic properties. The proposed action will include survey, diagnostics, 

and public education, as well as voluntary insecticide treatments by citrus 

growers. In addition, USDA and its cooperators may treat residential and 

noncommercial citrus areas with insecticides with the consent of 

residential landowners. The proposed action is not anticipated to disturb 

historic sites because it will be mainly carried out in agricultural settings 

or in residential areas. In the unlikely event that historic districts, sites, 

buildings, structures, or objects that are included in or eligible for 

inclusion in the National Register of Historic sites are in or near the 

treatment area, the State Historic Preservation Officer will be contacted 

prior to initiation of treatment of the proposed site.
68

VII. Listing of Agencies and Persons 

Consulted 

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Policy and Program Development

Environmental and Risk Analysis Services

4700 River Road, Unit 149

Riverdale, MD 20737

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Plant Protection and Quarantine

Emergency and Domestic Programs

4700 River Road, Unit 134

Riverdale, MD 20737

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Plant Protection and Quarantine

Center for Plant Health Science and Technology

22675 N. Moorefield Rd.

Edinburg, TX 78541

U.S. Department of Agriculture

Animal and Plant Health Inspection Service

Plant Protection and Quarantine

Citrus Health Response Program

920 Main Campus Drive, Suite 200

Raleigh, NC 27606
69

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Appendices
Appendix A. ACP and CG (Ca. L. asiaticus) Host Plants

Scientific Name

(Gutierrez, 2010) Common Name(s)

ACP and/or CG

(Ca. L. asiaticus) Host Plants

(Gutierrez, 2010)

Aegle marmelos Bael, Bengal quince, golden apple ACP host

Aeglopsis chevalieri Chevalier’s aeglopsis ACP and CG host

Afraegle gabonensis Chevalier’s aeglopsis, Gabon powderflask ACP host

Afraegle paniculata Chevalier’s aeglopsis, Nigerian 

powder-flask ACP host

Amyris madrensis Mountain torchwood ACP host

Atalantia species (including Atalantia 

monophylla)

Chevalier’s aeglopsis, Indian atalantia ACP host

Balsamocitrus dawei Uganda powder flask ACP and CG host

Bergera (=Murraya) koenigii Curry leaf ACP host

Burkillanthus malaccensis Malay ghost-lime CG host

Catharanthus roseus Vinca, Madagascar periwinkle CG host (laboratory only)

Choisya arizonica Arizona orange ACP host

Choisya ternate Mexican orange, mock orange, Mexican 

orange blossom ACP host

×Citrofortunella species (including 

×Citrofortunella microcarpa)

Limequat, calamondin, and Panama 

orange

ACP host

×Citrofortunella microcarpa Calamondin, Panama orange CG host

×Citrofortunella floridana ×Fortunella 

crassifolia Limequat and hybrid oval kumquat ACP host

×Citroncirus webberi Citrange CG host

Citropsis articulate African cherry orange ACP host

Citropsis gilletiana Gillet’s cherry orange ACP host

Citrus amblycarpa Nasnaran mandarin ACP and CG host

Citrus assamensis Ginger lime ACP and CG host

Citrus aurantifolia Key lime ACP and CG host

Citrus aurantium Sour orange, Seville orange, bigarde, 

marmalade orange ACP and CG host

Citrus deliciosa King orange ACP host

Citrus depressa Flat lemon ACP and CG host

Citrus halimii Papeda CG host

Citrus hassaku Hassaku orange CG host

Citrus hystrix Mauritius papeda, caffre lime, kaffir lime ACP host

Citrus ichangensis Ichant papeda, Ichang lime ACP and CG host

Citrus indica Indian wild orange CG host
Citrus jambhiri Jambhuri orange lime loose-jacket, 

rough lemon ACP and CG host

Citrus junos Yuzu, Japanese citron ACP and CG host

Citrus karna Karna, jaune orange ACP host

Citrus keraji Kabuchi, keraji, unzoki CG host

Citrus latipes Khasi papeda ACP host

Citrus limetta Tunisian sweet-lime, sweet-lemon, 

Moroccan limetta ACP and CG host

Citrus limettioides Sweet lime ACP and CG host

Citrus limon Lemon ACP and CG host

Citrus limonia Chinese lemon ACP and CG host

Citrus macrophylla Alemow CG host

Citrus macroptera Melanesian papeda CG host

Citrus madurensis (=×Citrofortunella 

microcarpa)

Calamondin or Panama orange CG host

Citrus maxima Pummelo, pomelo, shaddock, 

pompelmous ACP and CG host

Citrus medica Citron ACP and CG host

Citrus meyeri Meyer lemon, dwarf lemon ACP host

Citrus micrantha Biasing CG host

Citrus natsudaidai Japanese summer grapefruit ACP host

Citrus nobilis Tangerine ACP and CG host

Citrus obovoidea Kinkoji ACP host

Citrus oto Mandarin CG host

Citrus paradise Grapefruit ACP and CG host

Citrus pseudolimon Galgal lemon ACP host

Citrus reshni Cleopatra mandarine, Spice mandarin CG host

Citrus reticulate Mandarin, tangerine ACP and CG host

Citrus sinensis Sweet orange, orange ACP and CG host

Citrus sinesis x citrus reticulata Tangor ACP host

Citrus sulcata Sanbokan ACP host

Citrus sunki Sour mandarin, sunki mandarin ACP and CG host

Citrus tamurana Hyuganatsu ACP host

Citrus x tangelo Tangelo, ugli ACP and CG host

Citrus tankan Jiaogan ACP and CG host

Citrus unshiu Satsuma ACP and CG host

Clausena anisum-olens Citrus ACP host

Clausena excavate Pink wampee ACP host

Clausena harmandiana ACP host

Clausena indica Clausena ACP and CG host
Clausena lansium Wampee CG host

Clymenia polyandra Clymenia ACP host

Cuscuta species (including Cuscuta 

australis, Cuscuta campestris, Cuscuta 

pentagona, Cuscuta reflexa)

Dodder, lovevine, strangleweed, 

hellbind, goldthread, devil CG host (laboratory only)

Eremocitrus glauca Desert lime ACP and CG host

Eremocitrus hybrid (Citrus glauca x 

Citrus reticulata) ACP host

Eremocitrus specie X Citrus depressa ACP host

Esenbeckia berlandieri Berlandier’s jopoy ACP host

Feroniella lucida Feronia, Feroniella ACP host

Fortunella species Kumquat ACP and CG host

Fortunella x crassifolia Meiwa kumkuat ACP and CG host

Fortunella hindsii Hong Kong kumquat, wild kumquat ACP host

Fortunella japonica Marumi kumquat, Morgani kumquat ACP host

Fortunella margarita Oval kumquat, Nagami kumquat ACP and CG host

Fortunella x obovata Changshou kumquat CG host

Fortunella polyandra Malayan kumquat ACP host

Glycosmis pentaphylla Orange berry, Gin berry ACP host

Limonia acidissima Indian wood apple ACP and CG host

Merope specie Mangrove lime CG host

Merrillia caloxylon Flowering merrillia ACP host

×Microcitronella species Faustrimedin ACP host

Microcitrus specie ACP and CG host

Microcitrus australasica Finger lime CG host

Microcitrus australis Australian round lime ACP host

Microcitrus hybrid ACP host

Microcitrus inodora Large leaf Australian wild lime ACP host

Microcitrus papuana Round lime ACP host

Micromelum minutum Lime berry CG host

Murraya species Mock orange, orange-jasmine, Chinesebox CG host

Murraya euchrestifolia Mock orange ACP host

Murraya paniculata Orange-jasmine, Chinese-box ACP and CG host

Naringi crenulata Naringi ACP host

Nicotiana tabacum Tobacco CG host (laboratory only)

Pamburus missionis Mock orange ACP and CG host

Poncirus trifoliate Trifoliate orange ACP and CG host

Poncirus trifoliate x Citrus sinensis Citrange CG host

Ravenia spectabilis Lemonia, pink ravenia ACP host
Severinia buxifolia Chinese box orange ACP and CG host

Solanum lycopersicum Tomato CG host

Swinglea glutinosa Tabog ACP and CG host

Tetradium ruticarpum Evodia ACP host

Toddalia asiatica Orange climber plant ACP host

Triphasia trifolia trifoliate limeberry ACP and CG host

Vepris (=Toddalia) lanceolata White ironwood ACP host

Zanthoxylum beecheyanum Chinese pepper CG host

Zanthoxylum clavaherculis Hercules’ club, Southern prickly-ash ACP host

Zanthoxylum fagara White ironwood, Lime prickly-ash, wild 

lime ACP host
Appendix B. Positive ACP Counties and Temperature 

Suitability Map

The following is a map of U.S. counties where there has been a positive detection of ACP, as well 

as where ACP may or may not become established based on cold temperature mortality. 
Appendix C. U.S. Counties with Commercial Citrus

Production

Appendix D. Affected Environment for the Proposed 

ACP Control Program