Progress 10/01/06 to 09/30/11
Outputs
OUTPUTS: Deposition of insecticide sprays from various kinds of orchard sprayers and operational practices were studied in commercial apple orchards. Both fluorescent tracers and direct analysis of residues along with bioassays of first instar codling moth larvae were used to characterize initial deposition and persistence of bioactivity of insecticide residues. Active ingredients studied included azinphos-methyl (AZM) and acetamiprid. Both leaves and apples were analyzed and bioassayed. The studies were conducted over several years. Findings included, (1) Deposition was slightly higher in the mid-canopy level of trees; (2) Initial residues far exceeded lab determined LC50's & LC90's for codling moth neonates but dropped off over the following three weeks; (3) Skipping rows during spraying can maintain effective first generation codling moth control because AZM residues and bioactivity did not significantly differ on leaves collected from sprayed and unsprayed sides of trees; (4) Effective second generation codling moth control may be impeded by skip row spraying because in contrast to leaves, residues on apples and percentage reduction of CM feeding injury were significantly lower on apples from unsprayed sides of trees than sprayed sides of trees. This conclusion follows from published research showing egg laying of first generation moths is predominantly on leaves but increases substantially on apples during second generation egg-laying; (5) Significant residues were deposited on the ground; (6) Drift studies showed detection of residues about 200 ft from the orchard edge; (7) Backwash from an airblast sprayer would cause drift on the outside row even with nozzles turned off; (8) A retardant agent did not reduce drift but adjuvants did seem to affect deposition. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Tree fruit growers PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Drift from orchard sprayers is unavoidable but can be reduced by using skip row spraying. However, skip row spraying may be feasible only with the first generation codling moth and uncertain with second generation codling moth. Spraying the outside row with the outside nozzles turned off will not reduce drift owing to a backwash effect of residues moving over the sprayer. However, starting spraying between rows two and three will reduce drift. Adjuvants might be useful for reducing the volume of spray water needed but drift retardants may not be effective in reducing drift.
Publications
- No publications reported this period
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: A comprehensive review of agrochemical spray drift was conducted with an international team of scientists representing academia, industry, and government. Following is a summary of major conclusions. Spray droplets can drift beyond the intended target to non-target receptors, including water, plants and animals, during application of agrochemicals. Factors affecting this spray drift include mode of application, droplet size, which can be modified by the nozzle types, formulation adjuvants, wind direction, wind speed, air stability, relative humidity, temperature and height of released spray relative to the crop canopy. The rate of fall of spray droplets depends upon the size of the droplets but is modified by entrainment in a mobile air mass and is also influenced by the rate of evaporation of the liquid constituting the aerosol. The longer the aerosol remains in air before falling to ground (or alternatively striking an object above ground) the greater the opportunity for it to be carried away from its intended target. In general, all size classes of droplets are capable of movement off target, but the smallest are likely to move the farthest before depositing on the ground or a non-target receptor. It is not possible to avoid spray drift completely but it can be minimized by using best management practices. These include using appropriate nozzle types, shields, spray pressure, volumes per area sprayed, tractor speed and only spraying when climatic conditions are suitable. Field layout can also influence spray drift, whilst crop-free and spray-free buffer zones and windbreak crops can also have a mitigating effect. Various models are available to estimate the environmental exposure from spray drift at the time of application. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
This review of spray drift covered for the first time regulations in various countries outside of the United States. One output was an analysis of how spray drift is analyzed by governmental agencies in Europe, Australia, and Latin America.
Publications
- Felsot, A.S. 2010. Communicating safe pesticide use. Handbook of Pesticide Toxicology, 3rd edition. 3 ed. Elsevier, Inc. 1173-1187.
- Felsot, A.S., J.Unsworth, J.Linders, G.Roberts, D.Rautman, C.A.Harris, and E.Carazo. 2010. Agrochemical spray drift; assessment and mitigation--a review. Journal of Environmental Science and Health: Part B, Pesticides, Food Contaminants, and Agricultural Wastes. 45:889-911.
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: Interaction of meteorology and postspray volatilization of methamidophos (an organophosphorus insecticide) was considered in an assessment of the potential inhalation risk to children in an agricultural community. Source fluxes and dispersion modeling as influenced by local meteorology (especially temperature, wind speeds, and wind direction) provided variability in potential community exposure. Air sampling measurements of methamidophos were made before, during, and after a spray event. The exposure benchmark was acute inhalation risk for children living in an Eastern Washington State community in close proximity (between 15 and 200 m) to sprayed potato fields. Risk was estimated as the measured average air concentrations of methamidophos in the community relative to a "no observed adverse effect level" for subchronic inhalation. The baseline estimates of inhalation exposure were below the EPA level of concern based on a target margin of exposure (MOE) of 300. Because meteorological conditions during and after spraying influence the amount of material moving into areas where children reside, historical meteorological data were used to drive model simulations that predicted likely air residue concentrations under different wind and temperature conditions. A 2-D simulation of estimated air concentrations in the community near the fields was created by adding variability to the residue decay constant and initial emission fluxes. PARTICIPANTS: University of Washington faculty TARGET AUDIENCES: Federal & State Agencies, Ag Industry, farmworkers PROJECT MODIFICATIONS: This aspect of the project is complete.
Impacts
This work provided a methodological framework for using available meteorological data to assess air concentrations of pesticides from agricultural sprays in the absence of extended residue measurements. The deterministic as well as the probabilistic risk analyses in this study indicated that postspray volatilization in the specific spray situation analyzed (methamidophos applied on potato fields in Eastern Washington) did not pose acute or subchronic risks as defined by the EPA. However, this study did not consider any pathway of exposure other than inhalation (e.g. diet, dermal, etc.). A more complete risk assessment should also consider the latter exposure pathways.
Publications
- Ramaprasad, J., M.Tsai, R.A.Fenske, E.M.Faustman, W.C.Griffith, A.S.Felsot, K.Elgethun, S.Weppner, and M.G.Yost. 2009. Children's inhalation exposure to methamidophos from sprayed potato fields in Washington State: Exploring the use of probabilistic modeling of meteorological data in exposure asessment.. Journal of Exposure Science & Environmental Epidemiology 19:613-623.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: Four orchard air blast applications of phosmet on a Gala apple orchard were monitored in South Central Washington State. Deposition sampling was conducted using three transects and a supplementary sampling grid between and around the transects. The orchard air blast sprayer was tracked using a global positioning system (GPS). On-site meteorological data were collected. We found that deposition patterns in the sampling field differed significantly with changing wind direction. Using kriging to interpret our deposition data, we also found that the placing of transects perpendicular to the tree rows (as per U.S. EPA spray drift test guidelines) can significantly underestimate the deposition with distance compared with along-wind transects. The greater the angular deviation of the wind from being perpendicular to the tree rows, the greater the underestimation. Overall underestimation observed in our spray events ranged from 22% to 94%. Our kriging results also indicated that the use of transects alone does not adequately capture the deposition pattern across the sampling field. Using only the transect data in a mass balance calculation to estimate fraction deposited and fraction available for drift would overestimate near-field deposition on average by 19% and thereby underestimate far-field drift. Compared with along-wind transect data, the AgDRIFT orchard air blast model output consistently underestimated overall deposition by 88% to 100% for the spray events. PARTICIPANTS: M. Tsai M. Yost (Univ. of Washington) TARGET AUDIENCES: Tree fruit growers, regulators PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
This study demonstrated three shortcomings of EPA's guidelines for drift sampling: 1) use of transects perpendicular to the tree rows is biased towards an underestimation of deposition with increasing downwind distance; 2) use of transects also results in overestimation of near and across field deposition; and 3) overestimation in the near-field results in underestimation of mass available for longer range drift. These shortcomings can be remedied through the use of a regular sampling grid pattern that would take into account the normal variability of wind and cover more than just one side of an orchard.
Publications
- Felsot, A.S. 2008. Chemicals: Pesticides. Information Resources in Toxicology, 4th Edition. Ed. P.S. Wexler, S. Gilbert, B. Hakkinen, A. Mohapatra. 4th ed. San Francisco. Elsevier, Academic Press. 145-158.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Agricultural production can be limited by scarce resources (e.g., water and fuel) as well as societal concerns about worker exposure to pesticides and environmental contamination. Tree fruit growers spray pesticides to protect their crops from insects and diseases. They typically spray =100 gal/acre. Spray tanks generally hold from 300-1000 gallons, limiting the acreage that can be treated with one full tank. The more times that applicators fill the spray tank, then the greater will be their pesticide exposure as well as use of fuel and water. If orchard sprayers could deposit residues on apples effectively at lower spray volumes per acre, water and fuel use would be less and workers would be exposed to less concentrated pesticide product. However, farmers need to know if volume of the spray and use of adjuvants affects deposition of pesticide residues on the apples. To address the latter knowledge gap, two research objective were defined. (1) Determine if the volume of
insecticide spray (AI = phosmet formulated as Imidan WP) applied per acre affects residue deposition on apples. (2) Determine if the residues of the insecticide are affected by the type of adjuvant (Sylgard vs. In-Place) used at low (40 gal/acre) and high (190 gal/acre) volumes of spray. Except for the Sylgard treatment in the mid canopy location, spray volume seemed to not affect deposition of phosmet residues on apples. Furthermore, residues deposited on apples in the top of the canopy were not significantly different from those deposited in the middle of the canopy, even at the low spray volume.
PARTICIPANTS: Daniel Ramirez, American Chemical Society Project Seed Intern.
TARGET AUDIENCES: Growers Fruit Extension Agents Regulators
Impacts
Our research suggested that volume rate of spray using an axial fan airblast sprayer did not significanlty affect insecticide residue deposition. Thus, farmers can save resources by applying orchard insecticides in less water using their conventional airblast sprayers. Also, different adjuvants generally should not affect residue deposition sufficiently to affect insect control. The use of less water will require less fuel to control pests and result in less overall pesticide applicator exposure because of a reduction in the frequency that a tank must be refilled to spray a whole orchard.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
Experiments were conducted on a 5-acre block of Gala apples at a commercial orchard east of Prosser, WA. Three spraying treatments consisting of 25 trees were assigned across the first 12 rows of the orchard block: CONV (every tree row sprayed); ARM (every other row sprayed; i.e., one side of a tree row was left unsprayed); SR (skip row; one row completely left unsprayed and flanked by tree rows with only one side sprayed). Azinphos-methyl (AZM; formulated as Guthion) was applied to each spraying treatment. Samples of foliage and apples were collected to determine residue distribution and magnitude and its relationship with bioactivity against neonate CM larvae. Drift to ground was determined using silica gel plates laid along transects outside and within the orchard. Plates were also hung in trees to compare them to leaves and apples as collectors of residues. AZM residues did not significantly differ on leaves collected from sprayed and unsprayed sides of trees.
Residues were significantly lower on leaves from the untreated row of the SR treatment. Bioactivity followed a parallel trend with mortalities of neonate CM between 80 and 100% on leaves collected from sprayed and unsprayed sides of the tree. Thus, foliar residues and bioactivity did not differ among treatments, validating the main hypothesis of this study. In contrast to leaves, residues on apples and percentage reduction of CM feeding injury were significantly lower on apples from unsprayed sides of trees than sprayed sides of trees. Thus, the hypothesis of equivalence between CONV and ARM practices with regard to apples was not validated. Nevertheless, the results with foliage suggested that ARM spraying may be a viable practice in the PNW because CM females disproportionately lay their eggs on foliage around the apples and then must crawl over the leaf surfaces to search for an apple. Past work has shown that larvae die quickly after exposure to treated leaf surfaces (LT50 54
minutes). Thus, insecticide residues and bioactivity on leaves may make a major contribution to control of codling moth larvae in the field. Drift was detected to a distance of 200 feet from the field. However, drift was not different among the three spraying techniques. AZM residues on the ground within the orchard were lowest for the SR treatment, and the residues in the ARM treatment were lower than the CONV treatment.
Impacts
Insecticide residues on apples, even when every row is sprayed, may not be controlling neonate codling moth larvae efficiently. However, residues on leaves may be more important, especially considering that neonate CM lay the majority of their eggs on foliage surrounding apples. If the latter premise is valid, then growers may be able to cut pesticide use by adopting the alternative row middle spraying strategy. However, this method will not necessarily reduce the amount of drift downwind of the orchard.
Publications
- Felsot, A.S., and K.D.Racke. 2006. Chemical pest control technology: Benefits, disadvantages, and continuing roles in crop production systems. Crop Protection Products for Organic Agriculture. Environmental, Health, and Efficacy Assessment. Ed.
- Felsot, A.S., K. D. Racke. Washington, D.C. 2006 American Chemical Society. 1-18.
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