UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON, D

.C

. 20460 

## SEP 

## 16 2014 OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION
MEMORANDUM SUBJECT:

FROM: Information to supportregistration review ofdicrotophos: cotton crop phenology inthe southern U.S., recent dicrotophos use patterns, and potential alternative insecticides Nikhil Mallampalli, Ph.D., Entomologist

# ML~**· ,~--­**  Jonathan Becker, Ph.D., Senior Science Advisor**~)'**_,drvBiological Analysis Branch Donald Atwood, Ph.D., Entomologist

# .Jf~J! /Jt/.

# ~ Science Information and Analysis Branch Biological and Economic Analysis Division (7503P) TH,ROUGH: Amet Jones, Chief Biological Analysis Branch Diann Sims, Chief Science Information and Analysis Branch Biological and Economic Analysis Division (7503P) TO: Andrew Shelby, Environmental Scientist Nathan Miller, Environmental Scientist Mark Corbin, Chief Environmental Risk Branch 6 Environmental Fate and Effects Division (7507P) Thurston G

. Morton, Chemist, Elissa Reaves, Chief Risk Assessment Branch 4 Health Effects Division (7509P) Russell Wasem, Chemical Review Manager Neil Anderson, Chief Risk Management and Implementation Branch 1 Pesticide Reevaluation Division (7508P)
Page 1 of9BEAD Peer Review Panel date: August 27,2014 SUMMARY In this document, the Biological and Economic Analysis Division (BEAD) provides information on cotton phenology, cropping dates, dicrotophos application timing, and potential alternatives, for selected regions ofthe United States. BEAD recommends that this information should be used as input parameters when refining the modeling ofsurface water concentrations. BEAD also provides information related to the available alternatives for agronomically important pests treated with dicrotophos. INTRODUCTION Dicrotophos (Bidrin®) is currently the subject ofrisk assessment as part ofthe registration review process. The only agricultural use currently registered is cotton. Dicrotophos is a broad spectrum, partially systemic organophosphate insecticide that underwent reregistration review in 2002, and the reregistration eligibility decision was made final in 2006. After that review, only two uses remain registered: cotton and landscape tree injection. While dicrotophos was once widely used in cotton and other non-food crops (it was first registered in 1964), use in cotton declined by the early 2000s. One factor may have been that several insects once targeted with dicrotophos use, such as the cotton aphid and silverleafwhitefly, showed resistance to the material (Atwood 2012). Other factors probably contributing to a decrease in use ofdicrotophos in more recent years include the widespread adoption ofgenetically modified 

### Bt cotton (which effectively controls caterpillar pests), and the ramping down and eventual elimination ofthe boll weevil eradicationprogram in all states except Texas, which historically required prophylactic treatments with many different insecticides for season-long control (Stevenson and Matocha 2005, USDA 2009, APHIS 2013). However, since at least 2008, proprietary survey data indicate a slight increase in dicrotophos use nationally, with a proportionally greater increase in use (in terms ofacres treated and pounds of dicrotophos use) in southeastern states such as Georgia, North Carolina, and Louisiana. The major targets ofthisuse appear to be a complex ofstinkbug species, including the green stinkbug 

### (Acrosternum hi/are), the brown stinkbug 

### (Euschistus servus), and the southern green stinkbug 

### (Nezara viridula). All had historically been relatively minorpests until 

### Btcotton became widespread (Stevenson and Matocha 2005, Herbert et al. 2009). Use ofdicrotophos against the tarnished plant bug also continues at a comparatively high rate (in terms ofacres treated per year), but has declined compared to the 1990s, probably because ofthe spread ofresistant insects.
COTTON PHENOLOGY Cotton 

### (Gossypium spp.) is a perennial warm-season crop that requires a long growing period (USDA 2009). However, it is grown as an annual crop, with fields being mowed down and replanted each year. Figure 1below summarizes typical development ofcotton, with a focus on square and boll development, for cotton grown in the southern United States. A "square" is the
Page 2 of9developing cotton flower which, afterpollination, will give rise to the boll (the harvested part of the plant).

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### Figure 

### 1. Development ofcotton in the Mid-South with a May 1planting date, showing typical productionpatterns ofsquares, bolls and open bolls (NCCA 2014).

Based on the most recentplanting and harvest dates (USDA 2010) and on cotton phenology from the National Cotton Council (2014), Table 1below describes crop development datathat should be used for refinements to the drinking waterrisk models, for specific regional scenarios. 

### Table 

### 1.**Plantin~** and harvesting date for cotton in three states based on USDA (201 0). I·· 

### State Planting1 

### Emergencel Maturation3 

### Harvest' Mississippi 10-May 20-May 9-Jul 10-0ct North Carolina 10-May 20-May 9-Jul 1-Nov Texas 7-May 17-May 6-Jul 30-0ct Notes: 1. Planting date is the midpoint ofthe most active planting date range for each state from USDA (2010). 2. Emergence date is calculated by adding 10 days to the planting date. 3. Maturation date calculatedby adding 60 days to the planting date. The term "maturationdate" is used to refer to the date whenthe vegetative portion ofthe plant has developed to interceptthe maximum amount ofprecipitation. This is consideredto be equivalentto canopy closure. 4. Harvest date is the midpoint ofthe most active harvesting date range for each state from USDA (2010).

Page 3 of9DICROTOPHOS USAGE RELEVANT TO THE RISK ASSESSMENT BEAD examined recent extension service and research literature onthe impact ofstinkbug damage to cotton in orderto estimate when dicrotophos is likelyto be applied in this crop, since these insects are the majortarget pests for this pesticide use. The University ofGeorgia's 2014 Cotton Production Guide (UGA 2014) describes stinkbug damage to cotton as follows: "Stinkbugs havepiercingsuckingmouthparts anddamage cotton by feeding on the seeds of developing bolls. Stink bugs feed bypiercing the boll wallwith their beakandinjectinga digestive enzyme into the boll in or near the seedto soften or dissolveplanttissues so the bug can remove them. In addition tophysicaldamage, thisprocess allows for entry of rot organisms that contributes to degradation of bolls reducingyieldandquality. Bolls damagedbystinkbugs mayshow sunken, purple spots on the outside bollwall; however this is nota reliable indicator of stinkbugdamage. "In addition, "research suggests that in addition to yieldloss, excessive stinkbugdamage can reduce [desirable] fiber quality characteristics." This publication also points outthat "the number of bollsperplantwhich are susceptible to stink bugs is notconstantandvaries during the year. The greatest number of susceptible bollsper plantgenerally occurs during weeks 3-5 of bloom." As the season progresses, fewer susceptible bolls are present and the treatment threshold is adjusted to allow for more stinkbugs to be present before any insecticides are recommended. Many other factors affectthe number ofbolls vulnerable to stinkbug damage, however (e.g., drought), so the treatment scenario is potentially complex. This guide also states that "stinkbug infestations are often first observednear field edges (especially near apeanutplanting). Some innovative growers have chosen to scout and treat cotton near field edges independent of the entirefield" Dicrotophos is one ofthe few materials consideredhighly effective against stinkbugs (Ellsworth and Brown, 2013; Roberts and Toews, 2014; UGA, 2014; Reisig, 2014). Considering the description ofdamage and migrating behavior (above), it seems reasonable that growers dealing with these pests would apply dicrotophosjustbefore bloom or later inthe season when they detect insects moving in from nearby alternate hostplants. This may sometimes coincide with bloom (see Table 2). The typical application parameters that should be usedto reflect actual usage ofdicrotophos, based onproprietary usage data (Proprietary Pesticide Usage Data, 2008-2012), cotton phenology andtarget pestbiology are shownin Table 2 (below).

Page 4 of9

### Table 2. Recommended application parameters for modeling the use ofdicrotophos on MS, NC, and TX cotton. 

### State Rate Nu..-.berof Method Timing CalendarDates (lb a.i./A)**Applic~tions** 

### per Season Fint Second Application Application Mississippi 0.28 2* Ground First at 27 June 27 July (MS) pinhead squaring, Second at peak bloom North 0.22 1 Ground Pinhead 29 June


## ---- Carolina squaring (NC) Texas 0.24 2* Ground First at 27 June 27 July (TX) pinhead squaring, Second at

· peak bloom • Number of applzcatzons 1s roundedup from 1.4perseason basedon2008 to 2012propnetarypesticide usage data.


### TARGET PESTS AND PEST MANAGEMENT IMPORTANCE BEAD provides this discussion ofthe pest management role ofdicrotophos and its alternatives (section below) with a focus on its use in southeastern states, since these are the regions where use appears to be highest, and also include the ones mentioned above (Table 2). However, use of dicrotophos and some alternatives against the stinkbug complex, as described below, is also applicable to Arizona, where these pests have recently increased in importance (Ellsworth and Brown 2013). The label for dicrotophos on**co~on** states that it can be used to control the following insects: thrips, cotton fleahoppers, grasshoppers, boll weevils, stinkbugs, and plantbugs (all species). In addition, the label states that the following insects canbe "suppressed": aphids and spider mites. Historically, this insecticide has been used for all these pests (depending onthe region oryear considered). However, proprietary data onthe use ofdicrotophos in the past five years (2008- 2012) indicates that only the following arthropods have beenthe targets of usage on 5% oftotal acres treated ormore per year (on average): thrips, plantbugs, and stinkbugs. Ofthese the major targets appear to be the tarnished plant bug and stinkbugs (the species described in detail earlier in this memo; see page 2).

Page 5 of9DICROTOPHOS ALTERNATIVES Recent crop production guides from extension services in major cotton producing states, such as Georgia, North Carolina, and Texas, mention dicrotophos as an option to manage the following pests: thrips, plant bugs, and stinkbugs (USDA, 2009; Roberts and Toews, 2014; UGA, 2014; Reisig, 2014). Tables 3 and 4 (below) show major alternatives to selected target pests, as identified byproprietary data. Since growers appear to have mainly focused on stinkbugs and the tarnished plant bug in recent years ofdicrotophos use, these insects are also the focus ofthe information below. In additionthe data show only those alternatives that are also used at the same time as dicrotophos during boll development 

### (i

.e., the crop stages described in Table 2 above). As stated earlier in this memo, it appears that within the recent "pest spectrum" for dicrotophos use, the most important ones are those that comprise the complex ofstinkbug species that attack cotton bolls. For these insects, few effective alternatives seem to exist, though growers have used a variety ofmaterials as described above. The ones currently considered most effective, in addition to dicrotophos, are acephate and bifenthrin (alone or together), at maximum label rates, and bifenthrin premixed with zeta-cypermethrin (Ellsworth and Brown, 2013).
RECOMMENDATIONS BEAD recommends using the established planting, emergence, and harvest dates for cotton (Table 1) and the typical dicrotophos application parameters for rate, number ofapplications, and timing (Table 2).

Page 6 of9Table 

### 3. Alternatives to dicrotophos in use by cotton growers with the same timing as dicrotophos (see Table 2 above). This Table shows alternatives for the tarnished plant bug only. Only alternatives used on 5 percent ormore (total treated acres) are listed, based on proprietary data averaged . all 

### :tl natiOn ly orthe years 2008-2012.
Insecticide Chemical Class Percent Crop treated 

## * Acephate Organophosphate 158 Thiamethoxam Neonicotinoid 85 Bifenthrin Pyrethroid 83 Imidacloprid Neonicotinoid 60 Novaluron Chitin biosynthesis inhibitor 39 (insect growthregulator) Lambda-cyhalothrin Pyrethroid 25 Oxamyl Carbamate 23 Cypermethrin Pyrethroid 20 Cyfluthrin Pyrethroid 18 Flonicamid Nerve action (modulator of 15 chordotonal organs) Dimethoate Organophosphate 

### 7 Zeta-cypermethrin Pyrethroid 6
*Percentcrop treated is basedon totalacres treated, whzch includes acres treatedwith more than one application. Since these acres are cumulative, some materials showgreater than 100 % crop treated These data areprovidedonly to show the relative magnitude of use of each alternative, not for risk modelingpurposes..

Page 7 of9Table 4. Alternatives to dicrotophos inuse by cotton growers with the same timing as dicrotophos (see Table 2 above). This Table shows alternatives for the stinkbug complex only. Only alternatives used on 5 percent ormore (total treated acres) are listed, based onproprietary d t d 

### f all £ th 2008 2012

a a average na ton 1y or e years 

## -
,.,

' r. Insecticide Chemical Class Percent Crop treated 

### *

il' j 

## -· Bifenthrin Pyrethroid 100 Lambda-cyhalothrin Pyrethroid 53 Cyfluthrin Pyrethroid 43 Acephate Organophosphate 27 Zeta-cypermethrin Pyrethroid 27 Cypermethrin · Pyrethroid 25 Novaluron Chitinbiosynthesis inhibitor 22 (insect growth regulator) Imidacloprid Neonicotinoid 19 Thiamethoxam Neonicotinoid 8 Clothianidin Neonicotinoid 5 

### * Percent crop treated is basedon totalacres treated, which includes acres treatedwith more than one application. Since these acres are cumulative, some materials show greater than 100 % crop treated These data areprovidedonly to show the relative magnitude of use of each alternative, not for risk modelingpurposes.
REFERENCES CITED APHIS. 2013. Questions and Answers: Boll Weevil Eradication Program. USDA-APHIS Factsheet. Available onthe web at http:/ /www.aphis.usda.gov/publications/plant health/2013/fag boll weevil erad.pdf [Accessed July 2014]. Atwood, D. 2012. Review ofBenefits for Sulfoxaflorfor Fruiting Vegetables, Cucurbit Vegetables, Citrus, and Cotton

. (DP# 384640)

. Internal BEAD memorandum available through the Official Records database.

Page 8 of9Ellsworth, P. and L. Brown. 2013. Frequently Asked Questions: Brown Stink Bugs. Extension factsheet from the University ofArizona Cooperative Extension Service. Available onthe web at https://cals.arizona.edu/crops/cottonlfiles/BSB FAQlo.pdf [Accessed May 2014] Hebert, A., E. Blinka, J. Bacheler, J. VanDuyn, J. Greene, M. Toews, P. Roberts, and R.H. Smith. 2009. Managing Stinkbugs in Cotton: research 

### inthe Southeast Region. Publication#444-390 ofthe Virginia Cooperative Extension Service. Available onthe web at http://pubs.ext.vt.edu/444/444-390/444-390.html [Accessed July 2014]. NCCA. 2014 Overview. Integrated Crop Management. Advancing Cotton Education. Online publication ofthe National Cotton Council ofAmericaAvailable onthe web at http://www.cotton.org/tech!ace/overview.cfm Proprietary Pesticide Usage Data. 2008-2012. Reisig, D.D. 2014. Insect Control on Cotton. Pp 78-81 In: 2014 North Carolina Agricultural Chemicals Manual. Available onthe web at http://fsg.ces.ncsu.edu/publicationlnorthcarolina-agricultural-chemicals-manual/ [Accessed July 2014]. Roberts, P.M. and M. Toews. 2014. Cotton Insect Control. Pp 36-41 In: 2014 Georgia Cotton Production Guide. Available onthe web at www.ugacotton.com. Stevenson, D. E. and M.A. Matocha. 2005. A Pest Management Strategic Plan for Cotton Production in Texas. Available onthe web at www.ipmcenters.org [Accessed June 2014]. Stewart, S. and A. McClure. 2013. Insect Control Recommendations for Field Crops: Cotton, Soybean, Field Com, Sorghum, Wheat and Pasture. Publication# PB 1768 ofthe University ofTennessee Extension. Available onthe web at https:/ /utextension.tennessee.edu/publications

. [Accessed May 2014]. UGA. 2014. Cotton Production Guide. Publication# CSS-14-01 ofthe University ofGeorgia College ofAgricultural and Environmental Sciences Cooperative Extension. Available on the web at www.ugacotton.com. USDA. 2009. Crop Profile for Cotton in Texas. Available onthe web at www.ipmcenters.org

. USDA, 2010. Field Crops, Usual Planting and Harvesting Dates. Agricultural Handbook Number 628. National Agricultural Statistics Service, United States Department of Agriculture. Available onthe web at http:/ /usdaO 1.library.comell.edu/usda/current/planting/planting-10-29-201O.pdf [Accessed August 2014].

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