Application Methods in Orchards To Reduce Off-Site Deposition of

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Chapter 13

Application Methods in Orchards To Reduce Off-Site Deposition of Pesticides Robert C. Ehn,*,1 Dennis M. Dunbar,1 and Tim Ksander2 1R3 2Ag

Ag Consulting, LLC, 1629 Pollasky, Suite 111, Clovis, CA Advisors, Inc., 1695 Greenwood Way, Yuba City, CA 95993 *[email protected]

Two experiments were conducted during January and February 2006 in a dormant prune orchard near Live Oak, California, to evaluate off-site movement of Diazinon AG 500 Insecticide sprays using inward only spraying compared to spraying in two directions (inward and outward). Diazinon AG 500 Insecticide was applied at the labeled rate of 4.7 liters/ha. Applications were made on 25 January 2006, under a south wind blowing at 4.8 – 9.6 km/hr and on 3 February 2006, with southwest wind at 3.2 – 6.4 km/hr. Versi-Dry Lab Soakers (Kimbies) were used to collect the diazinon spray particles within the orchard and outside the orchard. Within the orchard, Kimbies were hung vertically in trees as well as placed horizontally under trees of the first tree row adjacent to the open field sampling area. Outside the orchard, Kimbies were placed horizontally on the ground at 7.6, 15.2, 30.5, 91.4, and 182.9 meters perpendicular to the first tree row. Samples were collected about 20 minutes after the applications in each experiment. There was 71.2% (Experiment 1) and 92.5 % (Experiment 2) less diazinon spray collected at all sampling stations from the inward only spray treatment compared to the two directional spraying. These results clearly show that inward only spraying of the outside three tree rows reduces the potential amount of total diazinon spray available (average of 81.9% from both experiments) for off-site movement when compared to the standard two-directional spraying.

© 2011 American Chemical Society Goh et al.; Pesticide Mitigation Strategies for Surface Water Quality ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

The amount of the total diazinon spray that moved off-site, however, for both the inward only and inward and outward spray treatments occurred in similar proportions. Considering both experiments, 25.6 to 28.7% of the total diazinon spray collected from the inward only and inward and outward treatments was collected off-site or outside the orchard. For both treatments, 99% of that spray that moved off-site was collected within 30.5 meters from the orchard. For the inward only treatment, the equivalent of 0.25 µg/dm2 was collected at 91.4 meters and 0.07 µg/dm2 was collected at 182.9 meters. For the inward and outward treatment, the equivalent of 3.4 µg/dm2 was collected at 91.4 meters and 0.8 µg/dm2 was collected at 182.9 meters. Far less diazinon spray was collected off-site at 91.4 meters and 182.9 meters from the inward only spray treatment when compared to the two-directional spray treatment. Spraying the last three rows of an orchard using inward only spraying results in >80% reduction in diazinon spray that potentially could move off-site.

Introduction Spray drift from orchards that are dormant and sprayed with organophosphate (OP) pesticides is considered to be one means for pesticide movement off-site and a potential source for contaminating surface waters. In a typical orchard spraying situation, air-blast sprayers are towed between rows of trees and spray is directed in two directions. When the sprayer approaches the edge rows of the orchard (those rows adjacent to the end of the planted orchard), drift can sometimes be observed to “overspray” the trees and drift past the edge of the orchard. Because the spray plume from air-blast sprayers is often very visible, the perception exists that there is a high level of drift from most orchard air-blast sprayer applications. The objective of this orchard air-blast sprayer study utilizing inward only spraying compared to conventional two-directional spraying is to quantify off-target movement from orchards sprayed during the dormant period with an OP pesticide. This study is designed to test the Best Management Practice as outlined in the Supplemental Label for Diazinon AG 500 Insecticide (EPA Reg. No. 66222-9) from Makhteshim-Agan of North America. The Supplemental Label for Diazinon AG 500 has directions to mitigate off-target movement of sprays such as:

Do not apply within 30.5 meters upslope of sensitive aquatic sites such as any irrigation ditch, drainage canal or body of water that may drain into a river or tributary unless a suitable method is used to contain or divert runoff waters.

190 Goh et al.; Pesticide Mitigation Strategies for Surface Water Quality ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

Apply only when wind speed is 4.8 – 16 km/hr at the application site as measured by an anemometer outside of the orchard on the side nearest and upwind from a sensitive site. When sensitive aquatic sites are downwind from orchards, spray the first three rows nearest the sensitive aquatic sites only when the wind is blowing away from the sites. The row at the edge of the field next to sensitive aquatic sites must be sprayed with the outside nozzles turned off. Spray must not be directed higher than the tree canopy and spray must be directed away from sensitive aquatic sites. In this study, off-site spray drift was measured after the first three tree rows on the edge of a commercial prune orchard were sprayed with nozzles operating in two directions (inward and outward) compared to when the spray was directed inward only (outside nozzles were shut-off). An open area downwind to the edge row of trees was designated as the sensitive aquatic site and used for sample collection.

Methods and Materials Prior to study initiation, the protocol for this study was submitted for review by the California Department of Pesticide Regulation. Orchard Two experiments were conducted about one week apart in a mature French prune orchard that was dormant near Live Oak, CA. The orchard was at Lomo Station about 8 km north of Yuba City on State Highway 99. Trees were 3.7 to 4.6 meters tall and approximately 14 years old. Tree spacing was 6.1 x 6.1 meters in a square configuration with the tree rows running east to west. The sample stations were north of the treated rows perpendicular to the direction of the tree rows. Diazinon AG 500 Insecticide was applied one time in each experiment at a rate of 4.7 liters/ha (1.12 kg/ha). An OMC air-blast orchard sprayer pulled by a John Deere 1010 tractor was used in each experiment. The OMC sprayer had 10 Teejet nozzles per side configured with 3,4,4,5,5,4,4,3,3,3 disks and 25 cores. (Note: Airblast sprayers use a combination of disc and swirl sizes to determining the output of the sprayer. Different combinations produce droplets of varying size. The higher the disc number, the greater the spray output) The sprayer was pulled at a speed of 3.2 km/hr with 120 psi delivering 935.3 liters of finished spray per hectare. Droplet sizes ranged from fine to coarse with most in the medium range. Experiment 1 The application was made on 25 January, 2006 at approximately 2:00 pm PST. The inward only treatment was applied first followed immediately by spraying in both directions (inward and outward). The two treatments were separated by 191 Goh et al.; Pesticide Mitigation Strategies for Surface Water Quality ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

about 219.5 meters with the inward only plot located on the west side of the prune orchard. At the time of spraying, there was a 4.8 – 9.6 km/hr south wind with an air temperature of 11.7º C. A diagram of the orchard, direction of spraying and sampling stations is provided in Figure 1.

Figure 1. View of Test Site Orchard – Aerial View


Experiment 2 This experiment was conducted in the same mature French prune orchard as Experiment 1, however on trees in the same rows, but about 18.3 meters further down in the orchard than in Experiment 1. The application was made on 3 February 2006 at approximately 10:00 am PST. The inward and outward treatment was applied first, followed by the inward only treatment. Wind speed was 3.2 – 6.4 km/hr from the southwest with an air temperature of 9.4º C.

Sampling As specified in the protocol, prior to each application, the Versi-Dry Lab Soakers (Kimbies) were placed in an open field at the pre-determined distances of 0, 7.6, 15.2, 30.5, 91.4 and 182.9 meters downwind of the application. Each Kimbie was 50.8 cm x 46.4 cm (2,357 cm2) in size and laid out horizontally on the ground on a piece of hard plastic (Figure 2). The Kimbies were held onto the plastic with paper clips. The hard plastic pieces were held in place with garden pins.

Figure 2. Sampling Sheet (Kimbie) on Hard Plastic Laid Horizontal on Ground


In-tree sampling was accomplished by hanging two Kimbies in each of three trees in each treatment. The Kimbies were 20 cm x 30 cm (600 cm2) in size and wrapped around a hard surface (PVC pipe) (Figure 3). In each tree, one Kimbie was hung in the upper 1/3 of the canopy and the second Kimbie was hung in the same tree in the lower 1/3 of the canopy.

Figure 3. Sampling Sheet (Kimbie) Wrapped Around PVC Pipe and Suspended in Tree Approximately 20 minutes after completion of the applications for each experiment, the Kimbies were picked up and placed into pre-labeled Zip-Lock bags. Each Kimbie was folded inward to prevent chemical treated surfaces from contacting the Zip-Lock bags. These samples were placed into coolers with Blue Ice and then transferred to a freezer, where they were held until delivery to the analytical laboratory. Samples from Experiment 1 were transferred to the laboratory on 31 January, 2006 whereas samples from Experiment 2 were transferred to the laboratory on 7 February, 2006. Samples were kept frozen with dry ice during transport to the laboratory. Analytical Samples were analyzed by Environmental Micro Analysis, Inc. (E.M.A.) in Woodland, CA. E.M.A. Inc. used EPA Method 8141 for analysis of the samples and detection of diazinon. Each Kimbie sample was cut into small pieces to fit into 194 Goh et al.; Pesticide Mitigation Strategies for Surface Water Quality ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

a wide mouth jar where 500 mls of petroleum ether/ methyl t. butyl ether at 1:1 were added to cover the sample. The jar was shaken and a vial of the solution was loaded for GC analysis. Sample results are reported by the laboratory as micrograms diazinon per Kimbie (µg/Kimbie). Kimbies from Experiment 1 were extracted on 2 and 8 February, 2006 and analyzed on 9 and 10 February, 2006. Kimbies from Experiment 2 were extracted on 15 February, 2006 and analyzed on 11 and 14 March, 2006.

Results Raw data obtained from E.M.A. Labs for Experiments 1 and 2 are summarized in Tables 1 and 2, respectively. There were three replicates for each sampling station in each experiment. All replicate data along with means and standard deviation of the mean are provided in the tables. Under tree for A and B data have been combined in this table to represent one “under tree” value for statistical purposes. As reported above, the Kimbies hung in the trees had less surface area than the Kimbies laid out horizontally on the ground. Therefore, the raw data were converted from micrograms per Kimbie (µg/Kimbie) to micrograms per square decimeter (µg/dm2) in order to present the data from all sample stations in the same units. A square decimeter (dm2) is equal to 100 square centimeters (100 cm2) and was a convenient conversion for data from these experiments. Results converted to µg/dm2 are shown graphically in Figures 4 and 5. In Experiment 1, there was a 4.8 – 9.6 km/hr south wind that blew out over the orchard and sampling area. This provided an excellent opportunity to collect in-orchard and off-site movement of the diazinon spray. Using mean collections from each sampling station, the total diazinon spray collected from all sampling stations was 581.9 µg/dm2 in the inward only treatment and 2,019.9 µg/dm2 in the inward and outward spray treatment. This represents 3.5 times less diazinon spray deposit collected from the inward only spray treatment than the inward and outward spray treatment. With the exception of the 15.2 and 30.5 meter collection stations, there was significantly more diazinon collected at each sampling station in the inward and outward spray treatment than in the inward only spray treatment. In Experiment 2, there was only a 3.2 – 6.4 km/hr wind and it was blowing from the southwest. This blew spray deposit out over the sampling area at an angle and not exactly perpendicular to the sampling stations as in Experiment 1. Using the mean total diazinon spray collected per station as demonstrated above for Experiment 1, there was far less diazinon collected from the sampling stations in each treatment than in Experiment 1. The results, however, were similar to Experiment 1 in that far more diazinon spray (13 times) was collected from the inward and outward spray treatment (998.4 µg/dm2) compared to the inward only spray treatment (75.1 µg/dm2). There was a significant difference between diazinon spray deposits collected at each sampling station through 30.5 meters. Collections of diazinon spray at stations located at 91.4 and 182.9 meters were not significantly different. 195 Goh et al.; Pesticide Mitigation Strategies for Surface Water Quality ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

Table 1. Converted Data – Off-Site Movement of Diazinon Spray from an Application Made to Dormant Prune Trees Utilizing Inward Only Spraying Compared to Spraying in Two Directions (Inward and Outward) (Experimnet 1: Live Oak, CA 2006)1− 5

Table 2. Converted Data – Off-Site Movement of Diazinon Spray from an Application Made to Dormant Prune Trees Utilizing Inward Only Spraying Compared to Spraying in Two Directions (Inward and Outward) (Experiment 2: Live Oak, CA 2006)1−5


Figure 4. Off-Site Movement of Diazinon Spray From an Application Made to Dormant Prune Trees Utilizing Inward Only Spraying Compared to Spraying in Two Directions (Inward and Outward) (Experiment 1: Live Oak, CA 2006)

Figure 5. Off-Site Movement of Diazinon Spray From an Application Made to Dormant Prune Trees Utilizing Inward Only Spraying Compared to Spraying in Two Directions (Inward and Outward) (Experiment 2: Live Oak, CA 2006) 197 Goh et al.; Pesticide Mitigation Strategies for Surface Water Quality ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

The fact that less spray deposit was collected in Experiment 2 than Experiment 1 was likely a direct result of less wind and the fact that the wind was blowing to the southwest which may have taken some spray off the direct line of the sampling stations. As shown in Figure 6, the total diazinon spray deposit collected from the inward only spray treatment was reduced dramatically when compared to the inward and outward spray treatment (71.2% reduction in Experiment 1 and 92.5% reduction in Experiment 2). These results clearly show that spraying the last three rows of an orchard using inward only spraying as described in the BMP for Diazinon AG 500 Insecticide results in far less spray that could potentially drift off-site from an application to trees during the dormant period. This was demonstrated in both experiments.

Figure 6. Off-Site Movement of Diazinon Spray From an Application Made to Dormant Prune Trees Utilizing Inward Only Spraying Compared to Spraying in Two Directions (Inward and Outward) (Experiments 1 and 2: Live Oak, CA 2006) In terms of where the diazinon spray deposits were collected, the majority of the spray collected from both experiments was in the orchard itself (tree top, tree bottom, and under the trees). For the inward only spray treatments, 78.3 and 70.6% of the total diazinon spray collected from Experiment 1 and Experiment 2, respectively, came from sampling stations within the orchard. For the inward and outward spray treatment, 80.9 and 61.7% of the total diazinon spray collected from Experiment 1 and Experiment 2, respectively, came from sampling stations within the orchard. The percentage of total spray collected outside the orchard (off-site) was similar for the inward only treatment (mean 25.6% for both experiments) and 198 Goh et al.; Pesticide Mitigation Strategies for Surface Water Quality ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

inward and outward treatment (mean 28.7% for both experiments). The key difference, however, is that there was far less spray moving off-site from the inward only treatment when compared to the inward and outward spray treatment (42 µg/dm2 vs. 384.2 µg/dm2). Considering that 25-29% of the total diazinon spray collected from both treatments was outside the orchard (off-site), where was it collected? As shown in Figure 7, over 80% of the spray deposit that moved off-site was collected within 15.2 meters of the orchard for both treatments and 99% was collected within 30.5 meters. Very small amounts were collected at 91.4 and 182.9 meters off-site. For the inward only treatment, the equivalent of 0.25 µg/dm2 was collected at 91.4 meters and 0.07 µg/dm2 was collected at 182.9 meters. For the inward and outward treatment, the equivalent of 3.4 µg/dm2 was collected at 91.4 meters and 0.8 µg/dm2 was collected at 182.9 meters.

Figure 7. Off-Site Movement of Diazinon Spray After an Application Made to Dormant Prune Trees Utilizing Inward Only Spraying Compared to Spraying in Two Directions (Inward and Outward) (Experiments 1 and 2: Live Oak, CA 2006)

Conclusions Spraying the outside three rows of a dormant prune orchard with sprays directed only inward resulted in 81.9% less diazinon spray collected at all sampling stations compared to the two directional spray (inward and outward) spray treatment. The percentage of the diazinon spray collected outside the orchard (mean of both experiments) was similar for the inward only (25.6%) and inward and outward (28.7%) spray treatments. However, the total amount of 199 Goh et al.; Pesticide Mitigation Strategies for Surface Water Quality ACS Symposium Series; American Chemical Society: Washington, DC, 2011.

spray collected in micrograms per square decimeter was significantly less in the inward only program versus the inward/outward trial. For each treatment, 99% of the diazinon spray that moved off-site was collected within 30.5 meters of the outside tree row. The results of this study support the BMP for Diazinon AG 500 Insecticide and show that off-site movement of spray can be reduced dramatically by utilizing inward only spraying of the last three orchard tree rows. The results of this study suggest that the use of inward only spray practices near sensitive areas where buffer zones less than 30.5 meters are in place significantly reduces the amount of pesticide deposited within the buffer zone. The benefit of inward only applications increases for products with reduced buffer zones. Further, the BMP states that the first three rows nearest a sensitive aquatic area should be sprayed inward only when the wind is blowing away from the sensitive area. In these experiments, the spray was blowing toward the sensitive area (sampling stations) in order to measure a “worst case” scenario for each treatment. If the BMP had been followed and the wind had been blowing away from the sampling stations, even less spray would have been collected from each treatment, providing even further support for the BMP for Diazinon AG 500 Insecticide. Inward only applications also provide a benefit to reduce surface runoff of pesticides as the transport mechanisms to surface water are a combination of drift and surface water runoff. This is especially important during the dormant spray season when storm water runoff is most problematic. Any application BMP that reduces total load on soil surface will also reduce amount of pesticide available to storm water or irrigation runoff.


Application Methods in Orchards To Reduce Off-Site Deposition of

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