This axial fan air-blast sprayer was modified with radial
fan heads to spray from above the tree canopy, a
configuration that overcomes the problem of significant
decline in spray efficacy in the upper canopy of the tree
with traditional spray setups. This rig was modified by
Andrew Dasso (pictured) and Ryan Billing (not shown) in
the Biological and Agricultural Engineering Department
at UC Davis.
Improving the accuracy and efficacy of spray application not only provides improved pest control and ultimately better returns to growers, but it can also reduce environmental impacts by minimizing off-site movement of pesticides through drift or deposition to the orchard floor.
Since 2010, the Almond Board has funded two complementary projects that preliminarily show that simple modifications, such as slowing sprayer speeds, reducing spray volume and modifying nozzle configuration, can significantly impact the efficacy of hullsplit sprays for in-season navel orangeworm control while reducing off-target movement.
Research spearheaded by USDA ARS entomologist Joel Siegel, Ph.D., of the Areawide Navel Orangeworm Program has shown that NOW spray efficacy declines significantly in the upper canopy because of the drop-off in spray coverage above 16 feet. Dr. Siegel’s research demonstrated that a slight speed increase from 2 to
2.5 mph reduced insecticide coverage by as much as 32%. Dr. Siegel’s research also suggests that the use of two nozzles at each position in a spray rig can significantly improve insecticide coverage and allow the applicator to apply insecticide at a reduced volume.
Ken Giles, Ph.D., with the UC Davis Department of Biological and Agricultural Engineering is leading complementary studies that found NOW survival rates were three times greater when spray was applied at rig speeds of 2.4 mph compared to 1.8 mph. These differences were most noticeable in nuts obtained from the upper canopy. Off-site spray drift was also slightly higher at the higher rate of speed.
This is a summary of an article that was published in Western Farm Press June 16, 2012, page 12, and online May 21. The full article is available on the Western Farm Press website.