How do fruit growers adjust spraying to fit the sizes of trees in their orchards?
“Trees have gotten smaller and canopy volume has decreased, but pesticide labels are still written in terms of so much per acre,” said Dean Polk, a Rutgers University entomologist who is its tree fruit IPM coordinator in New Jersey.
As products have gotten more expensive, growers have every reason to want to use less if they can and still feel assured they are getting adequate coverage and protection. Yet they are often frustrated when they seek advice.
“Extension people can’t make recommendations off the label,” Polk said. Not only is there potential liability, but growers themselves can’t afford to go off-label if they want companies to stand behind their products’ performance.
Still, growers can make adjustments that result in less active ingredient being applied per acre.
Polk moderated a panel discussion on the question involving three Eastern fruit growers during the Mid-Atlantic Fruit and Vegetable Convention.
The three are well known for their fruit growing proficiency. J.D. Rinehart grows 100 acres of peaches and 300 of apples near Smithsburg, Maryland, with his brother, John; Chris Baugher grows apples in Aspers, Pennsylvania; and Gary Mount and his wife, Pam, have 200 acres of fruits and vegetables they market directly from their farm, Terhune Orchards, in Princeton, New Jersey.
The old way
The standard spray recommendation was developed back in the days of large trees on seedling rootstocks. The recommendation for apples called for mixing the labeled rate of pesticide into 400 gallons of water, and that was to cover one acre to the point of liquid runoff. This was called a dilute spray, or 1X dilution.
However, researchers found growers didn’t need to haul that much water, and that fewer gallons could be used, so growers began using 2X, 3X, 4X, and 6X dilutions, cutting water to 200, 133, 100, or 76 gallons per acre—which would apply the label rate per acre in less water.
But as trees became smaller, growers cut gallons per acre as well, and that reduced the amount of active ingredient applied per acre. It all became quite complicated.