Biopesticides for management of borers in organic and conventional orchards

Eastern US tree fruit growers, facing limitations on pesticide inputs, are challenged by the lack of efficacious tools to control key-wood boring pests of cherries, peaches, and apples. Current borer management programs rely on trunk applications of the organophosphorous insecticide, chlorpyrifos, which is targeted for withdrawal by the USEPA. The development and implementation of effective approaches for borer control with biopesticides will make pome and stonefruit pest management programs more sustainable and profitable. In June 2008, nematode efficacy trials targeting Greater Peachtree Borer, Lesser Peachtree Borer and American Plum Borer in tart cherry and peach orchards, and Dogwood Borer in apple orchards began. Trees within orchard sites were selected based on canker size, presence of frass in cankers, and presence of pupal cases. The nematode, Steinernema carpocapsae, was applied in an organic-certified formulation with a hand-pump SOLO backpack sprayer. Application timings of nematodes corresponded with predicted larval susceptibility based on historic adult flight data. Two sampling methods were used to evaluate effectiveness. In fall 2008, Forty-eight percent of trees were destructively sampled using a chain saw. Damaged tree pieces were harvested, transported to the laboratory and exterior bark to inner cambium was searched for borer larvae. Remaining trees left standing in orchards were evaluated non-destructively in summer 2009 when larvae exit the trunk and leave behind exuviae. S. carpocapsae was found to control borers in tart cherry and peach orchards.