Lower volume, better efficacy

Giles’ project looks at off-site movement of applied sprays under various spray operations and sprayer configurations. This study finds that reducing spray volume of hullsplit sprays also appears to increase the efficacy of applied sprays while significantly reducing drift and deposition of sprays to the orchard floor, where they may find their way into nearby surface waterways.

He compared hullsplit sprays at a conventional volume of 100 gallons per acre with reduced application volume of 50 gallons per acre applied at the recommended 2-mile-per-hour speed.

Movement of pesticides to the orchard floor was cut in half for the 50 GPA rate versus the 100 GPA spray treatment. Spray drift was also reduced dramatically in the area surrounding the orchard footprint for the 50 GPA spray. Both treatments provided excellent control of NOW up to 14 days after treatment within the lower portion of the canopy. While NOW survival was less than 1 percent one day after treatment in the upper canopy, it was significantly higher two weeks after treatment, ranging from 5 percent to 11 percent, depending on the treatment.

Results from these initial studies suggest that minor changes to ground speed, spray volume, sprayer setup and nozzle configuration can have profound impacts on the efficacy of in-season sprays while improving the environmental stewardship of almond spray programs.

Results of these newer studies will need to be replicated over a number of years and various conditions. But initial findings are encouraging that improved control of navel orangeworm at hullsplit with selective chemistries while reducing environmental impacts is possible without significant changes or investment in capital equipment.