UNITED ST AT ES ENVIRONMENT AL PROTECTION A GENCY WA SHINGTON D.C., 20460

OFFICE OF PREVENTION, PESTICIDES AND TOXIC SUBSTANCES

ME MORANDUM
SUBJECT: Estimates of Crop Irrigation for Endothall Registration (DP# 369862 , 369863 )
FROM: Bill Phillips, II, Ph.D., Agronomist

Biological Analysis Branch
Derek Berw ald, Economist Economic Analysis Branch Biological and Economic Analysis Division (7503P)
THRU: Timothy Kiely, Chief

Economic Analysis Branch
Arnet Jones, Chief Biological Analysis Branch Biological and Economic Analysis Division (7503P)
TO: Sidney Jackson, Risk Manager Reviewer

Barbara Madden, Risk Manager Risk Integration Minor Use Emergency Response Branch Registration D ivision (7505P)

Product Review Panel : October 7, 2009Summary

EPA is evaluating a proposed use of the aquatic herbicide endothall for w eed control in irrigation canals. This memo provides estimates for the percentage of crops that may be exposed to endothall that EPA is reasonably certain will not be exceeded. Crops will be exposed to endothall by irrigation water, so the maximum percent that could be exposed is the share of production from irrigated land. Estimates, summarized in Table 1, are d erived using two methods. Where data on irrigated and dryland production are available, the estimates are based on the share of production from irrigated land, which is the maximum percent of the crop that could be exposed to endothall. Estimates using the share of production that is irrigated are provided for barley, corn, dry edible beans, peanuts, oats, rice, sorghum, soy beans, sugarbeets, sugarcane, and wheat. For crops of concern that do not have available data on irrigated and dryland production, B EAD uses the share of production grown in 17 w estern states where irrigation is used extensively and endothall use will be concentrated. Estimates based on production in the 17 w estern states are provided for apples, grapes, oats, green peas, w heat, waterm elon, and straw berries. In addition, BEAD revie we d the protocol for the residue trials and concludes that the resulting data are conservative. The trials used applications of treated irrigation wa ter applied through overhead sprinklers, which would res ult in high exposure to the edible portion of the crop. Many fields are irrigated with drip lines or a flood system, which would result in less of the treated water, and thus less pesticide, deposited on the crop. In the registrant’s field trials plant s amples were taken for residue testing from crops irrigated overhead using water that was treated the day of harvest ; this is not common practice under actual production conditions

.Table 1. Estimated Percent Crop Treated with Endothall for Dietary Ri sk Assessment

Share of Irrigated Production Share of

Production in West 1 Estimated

Percent Crop Treated for Dietary Risk Assessment Apple n/a 65 65 Fresh market n/a 78 78 Processing n/a 44 44 Juice n/a 49 49 Canned n/a 14 14 Barley for grain 36

- 36 Corn for grain 19

- 19 Dry Beans 2 32

- 32 Grape n/a 94 94 Fresh market n/a 99 99 Processing n/a 94 94 Green Peas n/a 11 11 Oats for grain 7 37 7 Peanut for nuts 42

- 42 Rice 100

- 100 Sorghum for grain 15

- 15 Soy bean for beans 9

- 9 Straw berry n/a 91 91 Fresh market n/a 89 89 Processing n/a 100 100 Sugarbeet for sugar 37

- 37 Sugarcane for sugar 54

- 54 Watermelon n/a 39 39 Wheat for grain 14 70 14 Source: USDA 2009a, 2009b, 2009c, 2009d, EPA calculations. 1 Arizona, Calif

ornia, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Texas, Utah, Washington, and Wyoming. Estimates are only provided for certain crops.

Background Endothall is an herbicide registered for control of plants in water bodies. It is currently registered for weed control in irrigation canals, but with the requirement that water cannot be released from the system or applied to crops for seven days after treatment. The Agency is currently evaluating a petition for tolerances on many irrigated crops to allow registration of endothall for use in irrigation canals to control aquatic weeds without the requirement that the treated w ater be held or contained prior to being used to irrigate a crop . Because this is a new use pattern for endothall, dietary risks must be estimated and analyzed. Normal methods for estimating the percent crop treated for a new pesticide are inappropriate in this case, because the pesticide is not directly applied to t he crop. Exposure occurs via irrigation w ater. Endothall will be used to control weeds in irrigation systems, not as treatment for the water in the systems. Most of the water that goes through a canal to irrigate crops will not be treated. Instead, endothall will be periodically injected into irrigation water to keep weed populations down. Because the water in the canal israpidly turned over, after several hours most if not all of the endothall will no longer be in the canal

systems. In addition, the use directions for endothall restrict applications to irrigation canals to once every seven days, and a maximum of six times per year. Due to the rate of endothall used, the number of applications, and the timing of applications the residue trials for endothall seem to be conservative to BEAD. This supposition is supported given the protocol used where crops were overhead irrigated six times with an inch of water containing the maximum concentration of endothall. After the final treatment the cro p w as harvested the same day, resulting in maximum endothall residue concentrations on the crop. From one of the registrants field protocols: “[d] uplicate control and treated samples of each commodity were harvested from the respective tests. Samples o f field corn forage, sorghum forage and wheat forage and hay were harvested 0 days after the second or third application (0 DAT). Samples of sweet corn forage, kennels plus cob with husks removed (K+CWHR) and stover, field corn grain and stover, sorghum grain and stover, and wheat grain and straw were harvested following the sixth application at 0 DAT (or at 1 DAT in one wheat test )

. ” 1 Under actual field production conditions, crop harvest is conducted only after a specified number of days after treatment. Due to standard agronomic practices this duration is extended when, f or exam ple , wheat is left to dry in the fields for some time before harvest, to reduce the moisture content . While in other cases crops such as grapes are not overhead irrigated when fruit are present, because additional moisture on the bunch can lead to fungal diseases. There is an additional consideration that should be given here and that is that much of the crops irrigated from surface water sources are done so by using some type of delivery system other than overhead sprinklers, systems such as flood or drip irrigation.
Me thod for Estim ating Percent Crop Treated For some crops, the estimates in this memo are based on yield and acreage data for irrigated and non

irrigated crops f

rom the 2007 Census of Agriculture (USDA 2009d). The estimates provided will be an upper bound on the percentage of crops that may have been irrigated with water from canals that were treated with endothall, because some of the irrigated crops are not gro wn in areas where endothall will be used. Other crops that are important to the dietary risk assessment do not have data on irrigated and non

- irrigated production available. For these crops, this memo provides estimates of the amount of the crop grown in 17 we stern states where endothall use is expected. These are states where substantial amounts of w ater are transported through open canal systems to be used for irrigation. It is these systems where weed control is im portant, and endothall is likely t o be used.
Estimates from the 2007 Census of Agriculture For select crops, the 2007 Census of Agriculture (USDA 2009d) provides estimates of the acres and yield from farms with irrigation, farms without irrigation, and farms where some of the crop is irrigated. Using this information we provide estimates of the share of production irrigated for those crops where the data are available. These crops are barley, corn, dry edible beans, oats, peanuts for nuts, rice, sorghum, soybeans, sugarbeets, sugarcane, and wheat.
Table 2 show s the estimated percent of the crop that has been irrigated for the food crops for which data are available. To estimate the production from the irrigated acres, the first step is to estimate the crop production from irri gated land. Using the data in Table 2 , we multiply the irrigated yield by the irrigated acreage, which is the acreage from farms where the entire crop is irrigated plus the irrigated acreage from

1 Registrant submission: 47520713. Arsenovic, M. (2008) Endothall (Hydrothol 191): Magnitude of the Residue on Grain Cereal Group (Except Rice): Lab Project Number: Z9768. Unpublished study prepared by Interregional Research Project No. 4. 590 pages.partially irrigated farms. To get an estimate of the share of the crop irrigated, w e divide this by an estimate

of total production. To estimate total production from the information in Table 2, w e multiply the yield by the acreage for each type of farm, and add these together. Taking wheat as an example, estimated production from irrigated farmland is (1,806,902 + 1,557,177) × 80.3 = 270,135,544 bushels, which is the numerator for our percentage calculation. Total estimated production is 1,806,902 × 80.3 + (1,557,177 + 3,703,599) × 42.7 + 43,865,291 × 37.0 = 1 ,992,745,133 bushels. Dividing estimates for production from irrigated land by the estimate of total production yields an estimate of the share of production that has been irrigated, in this case 14%. The estimates for all the food crops with available d ata in the census are in the last column of Table 2. Note that the data available in the Census of Agriculture only provides overall yields for farms where only part of the crop is irrigated, although it does provide total production and irrigated and dryland acreage data. For this analysis, BEAD assumed the yield from the irrigated acreage on partially irrigated farms to be equal to the average yield per acre from irrigated farms. This is a conservative assumption, because the im plied non

- irrigated yi eld is substantially lower than from dryland farms in all but one case 2 , which tends to inflate the estimates of the share of crop irrigated. These estimates are based on only one year of data. How ever, it is unlikely that the amount of acreage irrigat ed will change a large amount from one year to the next, because irrigation equipment is an expensive capital investment. Note that these are estimates of the amount of the crop irrigated, not the amount of the crop that may have endothall residues. No t all of the crop that is irrigated will be grown in areas where endothall is likely to be used, and even in the West, where endothall use for irrigation is expected, not all systems will necessarily be using endothall, a new method of control. Therefore, the share of crops that are actually exposed to endothall are likely to be lower than the estimates of irrigated acreage in Table 2.

2 The exception is peanuts, where the implied yield estimate is slightly higher than the dr yl and yi eld. The difference is less than 3%.Table 2. Share of Crop Production Irrigated Entire crop irrigated Part of crop irrig ated None of crop irrigated EPA Estimated Share of Production Irrigated a Average Yield Per Acre Acres Acres not Average Yield Per Acre Average Yield Per Acre Crop Farm s Acres Farm s irrigated irrigated Farm s Acres Barley for grain ( bushels) 3,566 605,340 100.0 675 136,135 155,262 53.3 15,607 2,625,220 49.9 36% Corn for grain (bushels) 17,927 6,103,769 180.0 20,984 7,053,000 6,435,486 150.0 308,849 66,656,287 144.3 19% Dry edible beans, excluding limas (cwt) 2,275 317,193 22.6 181 36,310 50,432 16.5 3,780 1,051,614 15.9 32% Oats for grain (bushels) 1,304 67,948 83.7 316 10,266 15,560 63.4 40,938 1,415,375 58.1 7% Peanuts for nuts (pounds) 1,301 251,564 3722. 5 1,080 167,225 186,723 3234. 1 3,801 595,052 2725. 8 42% Ric e (cwt) 6,084 2,758,792 72.0

- - - - - - - 100% Sorghum for grain (bushels) 2,092 443,599 86.9 2,391 401,615 670,030 74.7 21,759 5,254,590 69.2 15% Soybeans for beans (bushels) 7,007 2,175,069 45.3 13,326 3,062,006 3,396,716 40.8 258,777 55,282,0 30 40.2 9% Sugarbeets for sugar (tons) 1,535 387,224 30.0 60 7,451 20,424 24.2 2,427 838,718 23.4 37% Sugarcane for sugar (tons) 210 431,796 38.7 9 3,409 3,373 33.3 473 408,088 34.7 54% Wheat for grain, all (bushels) 7,695 1,806,902 80.3 7,518 1,557,177 3,703,599 42.7 145,597 43,865,291 37.0 14% Source: USDA 2009d and EPA Calculations

a Assumes irrigated acres on farms where only part of the crop is irrigated obtain the same yield as acres on farms where the e ntire crop is irrigatedCrop Estimates

Endothall residues on some crops are of particular concern to EPA based on residue trials and dietary habits. These crops are peas, w atermelon, straw berries, apples, oats, grapes and wheat. For these crops BEAD provides estimates of the proportion of the crop that is grown in the 17 western states, which are the states expected to be users of endothall in irrigation water. According to the Farm and Ranch Irrigation Survey (USDA 2004), almost 70% of the irrigated acreage in the United States is in the 17 w estern states, and about 87% of the irrigation water applied to crops is in these western states, which correspond to the states served by Bureau of Reclamation water projects. The share of the crop grown in the 17 western states can b e used as a crude measure of the share of the crop that may have come in contact with endothall. These estimates are the best that can be made with the available data, and they likely overestimate the crop that will encounter endothall treated water, because not all production in the we stern states will be irrigated with water from canals that have been treated with endothall. Not all irrigation systems will use endothall, some crop production is irrigated with wells that do not require w eed control, and s om e crops such as wheat and oats may be farmed without irrigation, even in the arid West. When possible (wheat and oats), the estimates provided in Table 2 above, based on the 2007 Census of Agriculture, are preferable.
The 17 w estern states are Ariz ona, California, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Texas, Utah, Washington, and Wyoming. It is in the West that large scale water delivery systems are important to agriculture; th ese are the systems that will use endothall for irrigation, as they are the systems that currently use acrolein or xylene, aquatic herbicides for which endothall may substitute. Agriculture in the East, where it is less arid, does not require large scale water transfers. BEAD does expect to see endothall use in the East, but primarily for drainage systems rather than irrigation water delivery systems where w ater will be applied to crops. Where available, estimates of the crop grown in the 17 w estern states are provided for different end

- uses of the particular crop. This information can be useful for dietary risk estimates, which are based on consumption of specific food products. The estimates of the amount grown in the 17 western states are provided i n Table 3.
Peas Only two western states are important producers of green peas for processing, which can appear in baby foods. In 2008, about 103,000 tons w ere produced in Washington State, and about 33,000 tons in Oregon. Production in these two sta tes was about 11% of US production of almost 412,000 tons (USDA 2009a).
Watermelon
Four w estern states produce enough watermelon to show up in the USDA data, Arizona, California, Oklahoma, and Texas. California and Texas produced about 6,100,000 cw t. and 6,000,000 cw

t. in 2008, respectively. Arizona produced almost 2,900,000 cwt., and Oklahoma only produced about 360,000 cwt. Together, the almost 15,400,000 cw t. of watermelon represented about 39% of US production of about 39,600,000 cw t. in 2008 (US DA 2009a).
Strawberries California is the major straw berry producing state in the United States. In 2008, California produced almost 23,000 cw t. of straw

berries, and Oregon another 238 cw t., the two together totaling about 91% of the total US producti on. About 89% of the fresh market straw berries come from the western states of California, Washington and Oregon, and almost all the processing straw berries come from the same three states, accounting for almost all straw berries used for processing (USDA 2009b). Apple Available data on apple production covers the production for the w estern states of Arizona, California, Idaho, Oregon, Utah, and Washington, with Washington being by far the largest producer. Combined these statesaccounted for about 65% of total US apple production in 2008, with over 59% of the total coming from Washington

alone (USDA 2009b).
Oats Data on oat production is available for 13 of the seventeen western states, with South Dakota being the largest producer in the West, and 3 rd in the country, with about 8.8 million bushels. In all, the western states produce about 37% of the nation’s oats (USDA 2009c). Grapes California was the largest producer of grapes in 2008, accounting for over 89% of total production. The 17 w est ern states combined accounted for about 94% of total production. Looking at the end uses of these grapes, the picture is similar. About 99% of fresh grapes w ere from the western states in 2008, and about 94% of the processed grapes. Of the grapes used f

or processing, California was the most important producer of wine grapes (about 99%) and seems to account for all dried grapes (USDA 2009b).
Wheat Wheat is widely grown in western states, with all 17 states appearing in the available production data. T ogether, the 17 w estern states account for about 70% of the total wheat production.

Table 3 . Share of Production of Specific Crops in the 17 W estern States, 2007

US Production We stern

States Production We stern

States Share Green Peas (Tons) 411,78 0 43,666 11% Wa term elon (1,000 cwt.) 39,551 15,387 39% Strawberries (1,000 cwt.) 25,317 22,913 91% Fresh Market 20,911 18,653 89% Processing 4,406 4,404 100% Apple (Million Pounds) 9,769 6,394 65% Fresh Market 6,304 4,911 78% Processing 3,372 1, 500 44% Juice 1,534 750 49% Canned 1,191 170 14% Oats (1,000 Bushels) 88,635 32,565 37% Grapes (Tons) 7,303,26 0 6,887,000 94% Fresh Market 985,200 976,050 99% Processing 6,304,35 0 5,944,650 94%
Wh eat (1,000 Bushels) 2,499,52 4 1,752,810 70% Sour ce: USDA 2009a, 2009b, 2009c, EPA Calculations The 17 W estern states are Arizona, California, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Te xas, Utah, W ashington, and W yoming.

Suggested Federal Register LanguageEPA is establishing tolerances on multiple commodities to support the application of the aquatic herbicide endothall

to be used in irrigation canals without a holding period.
For a new agricultural pesticide use, EPA typic ally estimates percent crop treated by comparison with the amount of use of other pesticides for the same crop or site. That approach is inappropriate for the new use for endothall, because the use is on irrigation canals rather than crops and EPA does no t have data on the frequency of use of aquatic herbicides on irrigation canals. Instead, EPA has estimated percent crop treated for endothall by estimating the percent crop irrigated w hich serves as an upperbound for crops that may be exposed to endothall in irrigation water. EPA used two m ethods to estimate percent crop irrigated. The preferred method, used where data on irrigated production are available, is an estimate of the share of total production that is irrigated. Estimates from this method are provided for barley, corn, dry edible beans, oats, peanuts, rice, sorghum, soybeans, sugarbeets, sugarcane, and wheat. Where data on irrigated production are not available, EPA estimated the percent crop irrigated by determining the percentage of Unit ed States production of a crop that is grown in 17 w estern states where endothall may be used. The 17 w estern states are Arizona, California, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, Oregon, South Dakota, Tex as, Utah, Washington, and Wyoming. These states are the states where large scale water projects predominate, and where other chemicals are used in canals for weed control. These types of irrigation projects are relatively rare in other parts of the country. Use of these estimates in the exposure assessment is conservative, because it is the equivalent of assuming 100% of irrigated crops have irrigated with water from endothall

- treated canals. In fact, even in areas with surface w ater delivery systems, al l irrigation canals may not be treated with endothall. Additionally, some crops, even in the heavily irrigated areas of the West, are not irrigated, such as dryland grain production.References

USDA 2004. US Department of Agriculture, Nation al Agricultural Statistics Service, The Census of Agriculture, Farm and Ranch Irrigation Survey (2003) Volume 3, Special Studies Part 1. November 2009. Available here: http://www.agcensus.usda.gov/Publications/2002/FRIS/index.asp USDA 2009a. US Departme nt of Agriculture, National Agricultural Statistics Service, Vegetables 2008 Summary. January 2009. Available here: http://usda.mannlib.cornell.edu/usda/current/VegeSumm/VegeSumm

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- 2009.txt USDA 2009b. US Department of Agriculture, National Agricultural Statistics Service, Noncitrus Fruits and Nuts 2008 Summary. July 2009. Available here: http://usda.mannlib.cornell.edu/usda/current/NoncFruiNu/NoncFruiNu

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- 2009.pdf USDA 2009c. US Department of Agriculture, National Agricultural Statistics Service, Crop Production 2008 Summary. January 2009. Available here: http://usda.mannlib.cornell.edu/usda/current/CropProdSu/CropProdSu

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- 2009.txt USDA 2009d. US Department of Agriculture, 2007 Census of Agriculture United States Summary and State Data Volume 1, Geographic Area Series, Part 51. February 2009, updated September 2009. Available here: http://www.agcensus.usda.gov/Publications/2007/Full_Report/Volume_1,_Chapter_2_US_State_Level/st9 9_2_032_032.pdf