Suppression of peachtree borer and lesser peachtree borer with entomopathogenic nematodes: Effects of application method and formulation

The peachtree borer (Synanthedon exitiosa) and lesser peachtree borer (Synanthedon pictipes) are major pests of stone fruits such as peaches, plums and cherries.  Applications of entomopathogenic nematodes have been reported to cause high levels of mortality in these pests.  Specifically, in prior research we demonstrated that fall applications of Steinernema carpocapsae can prevent peachtree borer damage at the same level as the chemical standard, chlorpyrifos.  In this study, we focused on comparing and optimizing application methods that growers might use when distributing nematodes to the target site.  For lesser peachtree borer, which attacks the tree aboveground, we had previously discovered that a sprayable gel (Barricade®) can protect entomopathogenic nematodes from adverse environmental conditions and thereby facilitate efficacious pest suppression.  In this study, we tested whether the sprayable gel could be applied simultaneously with the nematodes (S. carpocapsae) rather than as a post-application cover.  For peachtree borer, results indicated that all methods of nematode application (handgun, boom sprayer, and trunk sprayer) caused suppression at the same level as chlorpyrifos.  Also, in lieu of irrigation, we discovered that Barricade can be applied to the soil around the base of the tree.  In our experiment targeting lesser peachtree borer, a single application of diluted Barricade with nematodes was equally efficacious as Barricade used as a cover spray (that follows nematode application) and both nematode-Barricade treatments caused similar suppression relative to the chemical standard.  Our results indicate substantial promise for grower adoption of these tactics.