UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON, D,C. 20460 

APR I! 2012 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: BEAD Chemical Profile for Registration Review: Norflurazon (l05801)' , I 

FROM: 

THRU: 

TO: 

Sunil Ratnayake, Biologist ~""" II - A () / 

Biological Analysis Branch \:... '~IWJ r ~~ 

Jihad Alsadek, Economist ,7 / t...e-{ A- ~ rr~ Science Infonnation and Analysis Branch 

Derek Berwald, Economist ftf ("i).. \!lA" P 

Economic Analysis Branch \j J V0 

Biological and Economic Analysis Division (7503P) 

Arnet Jones, Chief 

Biological Analysis Branch 

Diann 

Science 

Sims, 

Infonnation 

Chief ~~~ and AnalQYSiS Branch """'-

Timothy Kiely, Chief . 

Economic Analysis Branch 

Biological and Economic AnalysIS ivi~ Jack Brennan, Chemical Review Manager 

Risk Management and Implementation Branch 4 

Pesticide Re-ev~uation Division (7508P) 

Product Review Panel date: March 14,2012 

INTRODUCTION 

The purpose of this document is to convey usage infonnation and a broad overview of the pest 

management roles of pesticides that are beginning to undergo registration review. The 

anticipated audience consists of the team of EPA staff currently evaluating the registration status 

of norflurazon and eventually the general public. This document builds upon the data already 

provided in the "Usage and Label Use Data Packages" that are also provided to Registration 
Review teams by BEAD. The document is based on information and data available t9 BEAD as 

of March 7, 2012. 

Norflurazon was fITst registered as a pesticide in the U. S. ill 1974 (USEPA, 1996). Norflurazon 

belongs to,.the pyridazinone herbicide family. It interferes with carotenoid synthesis and causes 

chlorophyll depletion which inhibits photosynthesis in susceptible weeds. It is applied as a preemergence treatment to control grasses and broadleaf weeds in many agricultural and nonagricultural sit s which are described below. . 

COMMON FORMULATIONS AND APPLICATION METHODS 

Norflurazon is formulated as water dispersible granules and water soluble concentrate. This 

herbicide can be applied using tractor mounted ground sprayers and it should not be applied 

through any type of irrigation system. Norflurazon can be applied aerially with the use of drift 

control measures. 

USE SITES 

Agricultural Use Sites 

Norflurazon is labeled for use on bush berry, cane berry, grapes, citrus, nut crops, pome fruits, 

stone fruits, hops, asparagus, alfalfa, avocado, cotton, peanuts, soybeans, wheat, pasture, and 

uncultivated agricultural areas. 

Non-Agricultural Use Sites 

Norflurazon is labeled for use on ornamental plants, woody shrubs, trees, and non-agricultural 

areas. 

USAGE 

Agricultural 

The long term average use for the period 2000-2010 is about 915,000 lbs. a.i. per year on about 

609,000 acres for an average rate of about 1.5 lbs. a.i. per acre. Over this time period, oranges 

have been the largest use site with about 45% of the amount used. Cotton, almonds, and apple 

each have accounted for 8-9% of the pounds applied, see Figure 1. Use may have stabilized over 

the last five years (2006-2010), see Figure 2. Total use ofnorflurazon has been declining and the 

decline appears to be common across all crops although with some variation. Comparing the 

2000-2005 period to the 2006-2010 period (Figure 2), we can see that use on cotton declined 

over 90%, use on almonds declined over 60%, and use on oranges declined about 40%. Note 

that between the same periods, cotton acreage declined by 23 %, orange acreage declined 16%, 

and almond acreage grew by 26%. 

(Calculated from Proprietary Data, 2000-2010). 

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Figure 1. Agricultural Usage Data for Norflurazon in Pounds Active Ingredient (2000-

2010) 

PoundsA.I. 

700,000 -r--------- --------------

o 

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 

Years 

• Almonds 

• Apples 

• Cotton 

• Oranges 

• Other 

Other crops include grapefruit (4%), wine grapes (3%), raisin grapes, plums/prunes, and peaches 

(2% each), walnuts, pears, and cherries (1 % each). 

Source: Proprietary Data, 2000 -2010 

Figure 2. Usage in Pounds Active Ingredient for Norflurazon, All Crops, 2000-2010. 

2,500,000 ..-------------------------------

PoundsA.I. 

o"+--~r--~--~--~-_,--_r--,_--r_-~--~-__, 

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 

Years 

Other crops include grapefruit (4%), wine grapes (3%), raisin grapes, plums/prunes, and peaches 

(2% each), walnuts, pears, and cherries (1 % each). 

Source: Proprietary Data, 2000 -2010 

From 2006-2010, the annual total agricultural usage ofnorflurazon averaged approximately 

540,000 pounds active ingredient (a.i.) for 300,000 treated acres with an overall application rate 

of 1.7 lbs. a.i. per acre. Application rates have gone up over time. Data show rates on individual 

crops are not changing and this is due to a shift in the crop mix. Use on cotton, with a very low 

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rate has all but disappeared, while the use on oranges which has a high rate has become a larger 

share of use. 

(proprietary Data, 2006-2010). 

Figure 3 provides usage data for 2006-2010. During this period, the use ofnorflurazon on 

almonds and apples mildly fluctuated. The use on oranges peaked in 2009. BEAD could not 

identify exact factors which contributed to these changes in usage. For other crops, use varied 

from year to year, but there was no clear upward or downward trend. 

Figure 3. Agricultural Usage Data for Norflurazon in Pounds Active Ingredient (2006-

2010) 

800,000 -r----------------------

PoundsA.I. 

o 

2006 2007 2008 

Years 

2009 2010 

• Alfalfa 

• Almonds 

• Apples 

• Oranges 

• Other 

Other crops include wine grapes (4%), grapefruit and raisin grapes (3% each), peaches, pears and 

cotton (2% each), cherries, and plums, prunes, and walnuts (1 % each). 

Source: Proprietary Data, 2006-2010 

During this time frame, the crops with the most use in terms of total pounds of active ingredient 

applied are oranges (56%), apples (11 %), almonds (7%), and alfalfa (6%). The crops with most 

total area treated (TAT) are oranges (43%), alfalfa (12%), apples (11%), and almonds (10%). 

Since the percent of pounds applied to oranges is greater than the percent of area treated, we can 

infer that the application rate on oranges is higher than the overall average. In contrast, the 

application rate on almonds is lower than the overall average since the share of acres treated is 

larger than the share of pounds applied. The higher rate used on oranges is largely behind the 

increased average rate as oranges now make up a higher percentage of use. 

On average, the states with the most agricultural usage in terms of pounds a.i. applied are Florida 

(53%), California (26%), and Washington (11 %). 

(proprietary Data, 2006-2010). 

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Use Intensity 

Another measure of usage is the use intensity. In this analysis, the use intensity is expressed as 

the pounds a.i. applied per acre of land in farms. This differs from the application rate, which is 

expressed as the pounds a.i. applied per treated acre. Figure 4 represents norflurazon's use 

intensity in the US. The most intense use ofnorflurazon appears to be in Florida and California 

with small areas of intense use also reported for New Jersey and New York. 

Figure 4. Norflurazon Usage by Crop Reporting District (2006 - 2010) 

Average Pounds Per 

1,000 Acres of Farmland 

_ <1.4 

. 1. 4-3 . 5 

0 3. 6-65 

6. 6-12. 0 

12. 1 - 50 

Source: Proprietary Data, 2006-2010 

N 

! 

"~ 

This is a map of agricultural pesticide usage at the Crop Reporting District (CRD) level. CRDs 

are boundaries created by USDA NASS which are aggregates of counties (USDA, 2010). 

Pesticide usage is displayed as average pounds (for the years 2006-2010) per 1,000 acres of 

farmland in a CRD to normalize for the variation in farmland between CRDs. Farmland acreage 

was obtained from USDA (2007). 

Usage is based on private market surveys of pesticide use in agriculture (Proprietary Data, 2006-

2010). The survey data are limited to the states that represent the top 80-90% of acreage for the 

individual crops; therefore, use may be occurring in regions outside the scope of the survey. CRDs 

showing no usage of pesticides may be due to either the lack of pesticide use in the region or nonparticipation in the agricultural surveys. In addition, across the years, there may be variations in 

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the specific crops included in the CRD survey. This may result in a lower annual average for the 

CRD. 

Non-Agricultural 

In 2003, the reported non-agricultural use of norflurazon included 900 lbs. a.i. on all nurseries 

and floriculture, and 400 lbs. a.i. each for nursery propagation and cut cultivated greens. Usage 

for deciduous flowering trees totaled 2,000 lbs. a.i. with an application rate of 3.0 lbs. a.i. per 

acre. In 2006, the use of norflurazon was 4,200 lbs. a.i. on all nurseries with an application rate 

of 3.0 lbs. a.i. per acre. (USDA Agricultural Chemical Usage Nursery and Floriculture 

Summary) 

BIOLOGICAL ASPECTS RELEVANT TO NORFLURAZON 

Norflurazon can be applied as pre-plant incorporated and pre-emergence surface applications. 

Application of norflurazon on stressed cotton, peanut, or soybean plants at the early stage of 

development can cause temporary bleaching of leaves. Norflurazon belongs to the mechanism of 

action of group 12 (inhibition of carotenoid synthesis) under the WSSA classification and it has 

been reported that certain biotypes ofhydrilla (Hydrilla vertic illata) have developed resistance to 

this mode of action in the United States (Heap et aI., 2012). However, observed resistance was 

not specifically for norflurazon and presence of terrestrial weed specie with resistance to the 

mode of action of this herbicide is not reported in the United States (Heap et aI., 2012). 

HISTORY OF BEAD ASSESSMENTS FOR NORFLURAZON 

There is no record of prior BEAD assessments for norflurazon, so the relative importance of 

norflurazon to weed control has not been evaluated. However, the concentration of use in orange 

and almond suggest that noflurazon maybe be important to these crops, even though the percent 

of the crop treated is not particularly high. Another crop with relatively high percent of the crop 

treated is blueberry, which may indicate a niche use for noflurazon. 

DATA NEEDS RELEVANT TO BEAD'S FUTURE WORK ON NORFLURAZON 

Additional infonnation on norflurazon's use on ornamental plants, woody shrubs, trees, and 

aquatic sites, uncultivated agricultural and non-agricultural areas, such as pounds active 

ingredients used and application rates, would improve future BEAD assessments of the 

importance of norflurazon and may be needed as part of the registration review of this pesticide. 

REFERENCES: 

Heap, I, H. Glick, L. Glasglow, and W. Vencill. 2012. Herbicide Resistant Weeds by Country 

and Site of Action. 2012. http://www.weedscience.org/summary/countrysummary.asp 

Proprietary Data, 2000-2010. 

USDA. 2004. Agricultural Chemical Usage. 2003. Nursery and Floriculture Sump1ary. 

6 
USDA, 2006-2010. NASS Crop Reporting Districts. Online: 

http://www.ers.usda.gov/briefing/anns/resourceregions/resourceregions.htm#nass. 

USDA. 2007. Agricultural Chemical Usage. 2006. Nursery and Floriculture Summary. 

USDA, 2007. Census of Agriculture. Online: 

http://www .agcensus. usda.govlPublications/2007 /index.asp. 

USEPA. 1996. R.E.D. Facts. Norflurazon. 

http://www.epa. gOY /oppsrrd 1 /REDs/factsheets/0229fact.pdf. 

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