Surface Water Loading from drift of Aerially-Applied Malathion in Cherry Production

1. Surface Water Loading from drift of Aerially-Applied Malathion in Cherry Production Jeffrey Jenkins Department of Environmental and Molecular Toxicology

2. Cherry production in Wasco County, Oregon • Wasco County Oregon contains nearly 9,000 acres of cherry orchards, concentrated near The Dalles. • Pest management includes the use of organophosphate insecticides, applied by airblast ground sprayers or fixed-wing aircraft. • Cherry fruit fly quarantine requires Oregon Dept. of Ag approved pest management practices.

3. Water Resources of the Middle Columbia-Hood subbasin (8-digit HUC 17070105) • Salmon bearing streams • Court-ordered buffers: • 100 ft – ground • 300 ft – aerial • New label restrictions?

4. What is spray drift? “Spray drift is the physical movement of pesticide droplets or particles through the air at the time of pesticide application or soon thereafter from the target site to any non- or off-target site.” EPA, National Coalition on Drift Minimization

5. Factors Influencing Pesticide Drift • Droplet size (spectrum) • Release Height • Crop canopy • Landscape • Weather (temperature, humidity, wind speed/direction, atmospheric stability) • Sensitive areas?

6. How can spray drift be controlled? • Best Management Practices for drift reduction: • Monitor weather • Application practices • Drift Reduction Technology • Buffers and vegetative barriers • Identify sensitive areas

7. Reducing spray drift using vegetative barriers

8. Barrier should act as a filter Solid barriers may direct spray over the barrier - drift further?

9. Wind Patterns Near Treelines Adapted from Survey of Climatology: Griffiths and Driscoll, Texas A&M University, 1982

10. Collaborators: Philip Janney, Kelly Wallis, Helmut Riedl • We evaluated the effectiveness of adapted and native woody plant species as drift barriers between cherry orchards and surface water resources in Wasco County, Oregon. • Two sites were chosen: Three Mile Creek and Mill Creek. • Sites were chosen based on prevailing wind patterns, and comparable riparian areas with and without vegetation. At both sites the orchards slope down to the creek. • Depositional sampling used to estimate malathion stream concentrations.

11. Application • Malathion ULV was aerially-applied with an Airtractor-AT 402 equipped with 2 ASC-A10 rotary atomizers at a rate of 16 oz/acre • Droplet volume mean diameter 30-100 microns

12. Two sample sites selected based on prevailing wind patterns and riparian vegetation.

13. Spray Deposition Samplers • 23 cm x 26 cm Whatman No. 1 filter paper mounted on rectangular aluminum brackets • Mounted horizontally and vertically at height of 5 m • 2 transects of 4-5 samplers placed at each site • Weather: wind speed, wind direction, and temperature were monitored • Ethyl acetate extraction and analysis by gas-chromatography with mass selective detection; limit of detection 0.01 µg/cm2

22. Estimated Stream Concentrations • Malathion concentrations in the streams were estimated using a unit volume approach. • Both Mill Creek and Three Mile Creek are second order streams that have comparable dimensions. However, Three Mile Creek was dammed at the sampling site, altering the natural geomorphology of the stream. • The dimensions of Mill Creek were used to estimate the unit volume for both creeks. • The unit volume was determined using the dimensions of the collectors and the depth of the stream, such that the unit volume is:

23. Estimated Stream Concentrations • Assume that malathion deposited on the V1 and O1 collectors closest to the stream = water deposit, uniformly mixed into the static unit volume of water. • Estimate malathion concentration in the unit volume by:

24. Estimated Stream Concentrations

25. Project funding and support • Funded by EPA Region 10 Regional Geographic Initiative Program to • Wy’East Resource Conservation and Development • Additional support from OSU Agricultural Research Foundation, and • Mid-Columbia Orchardists