Efficacy of Steinernema carpocapsae for control of the lesser peachtree borer, Synanthedon pictipes: Improved aboveground suppression with a novel gel application

Abstract

Safe and effective tactics are needed for control of the lesser peachtree borer, Synanthedon pictipes (Grote & Robinson), which is a major pest of stone fruits ( Prunus spp) in eastern North America. Virulence of the entomopathogenic nematode, Steinernema carpocapsae (Weiser) , to S. pictipes has been demonstrated in the laboratory. However, achieving field efficacy has been difficult because S. pictipes attacks the tree aboveground where nematodes are subjected to damaging environmental conditions, e.g., UV radiation and desiccation. We investigated the potential of various formulations to improve the efficacy of aboveground applications. First, we screened five potential adjuvants at 2%, 20%, and 40% concentrations in water for toxicity to S. carpocapsae in the laboratory: Anti-Stress, Moisturin®, Nu-Film®, Shatter-Proof, and Transfilm®. In general, the adjuvants did not adversely affect nematode survival except at the highest rate. Subsequently, Shatter-Proof was tested in field trials in 2008 and 2009. S. carpocapsae was applied alone or with Shatter-Proof to peach limbs pre-infested with S. pictipes larvae. Furthermore, the experiments included the following treatments: S. carpocapsae followed by a post-application covering of latex paint, moistened diaper, or a gel spray (Barricade®). Controls of water-only, or water plus Shatter-Proof, Barricade®, or paint (without nematodes) were also included. The nematodes-only treatment failed to reduce S. pictipes survival relative to the water-only control in either year. Additionally, the nematode treatments with Shatter-Proof or paint did not differ from nematodes-only, water-only or their respective control treatments without nematodes. The diaper treatment with nematodes showed some potential as an efficacy enhancer (e.g., insect survival was reduced relative to nematodes-only in one year). In contrast, in both years, nematodes plus Barricade® reduced S. pictipes relative to the controls and the nematodes-only treatment; survival in the Barricade® treatment was 30% and 0% in 2008 and 2009, respectively. We conclude that nematode treatments followed by application of a sprayable gel such as Barricade® can enhance control of S. pictipes and possibly other aboveground pests as well.