Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2016
Publication Date: 10/1/2016
Citation: Shapiro Ilan, D.I., Cottrell, T.E., Mizell, R.F., Horton, D.L. 2016. Curative control of the peachtree borer using entomopathogenic nematodes. Journal of Nematology. 48(3):170-176.

Interpretive Summary: The peachtree borer is a major pest of peach, plum nectarine, cherry and other stone fruit trees. The insect lays eggs at the base of the tree and larvae bore into roots below the soil surface. Currently, methods to control this pest rely on broad spectrum chemical insecticides. Generally, control measures for peachtree borer are applied in the late summer or fall to prevent damage to the tree. However, it is possible to still see harmful borer infestations in the spring, and these infestations can be severe. Therefore, curative spring-time applications to control peachtree borer would be beneficial. However, such curative measures do not exist. Our objective was to develop safe and effective methods to control peachtree borer in a curative manner (i.e., through spring-time applications). Our experiments were conducted in Georgia peach orchards. We compared the standard chemical insecticide that is used in fall applications, chlorpyrifos, with entomopathogenic nematodes. Entomopathogenic nematodes, also known as beneficial nematodes, are small worms that can be used as environmentally-friendly bio-insecticides. Our results indicated that the beneficial nematodes provided high levels of peachtree borer control (about 80% or higher), whereas chlorpyrifos failed to control the pest. Also, we demonstrated the nematodes can be applied using standard spray equipment commonly used by peach growers. In conclusion, our study indicates that beneficial nematodes may be used as an effective “clean-up” measure for peachtree borer infestations. These findings are important because increased use of effective biological control strategies in agriculture, such using beneficial nematodes, is desirable for developing improved sustainable agricultural systems.

Technical Abstract: The peachtree borer, Synanthedon exitiosa, is a major pest of stone fruit trees in North America. Current management relies upon preventative control using broad spectrum chemical insecticides, primarily chlorpyrifos, applied in the late summer or early fall. However, due to missed applications, poor application timing or other factors, high levels of S. exitiosa infestation may still occur and persist through the following spring. Curative treatments applied in the spring to established infestations would limit damage to the tree and prevent the next generation of S. exitiosa from emerging within the orchard. However, such curative measures for control of S. exitiosa do not exist. Our objective was to measure the efficacy of the entomopathogenic nematode, Steinernema carpocapsae, as a curative control for existing infestations of S. exitiosa. In peach orchards, spring applications of S. carpocapsae (obtained from a commercial source) were made to infested trees and compared with chlorpyrifos and a water-only control in 2014 and 2015. Additionally, types of spray equipment were compared: nematodes were applied via boom sprayer, handgun, or trunk sprayer. Results indicated that S. carpocapsae provided significant curative control (e.g., > 80% corrected control for the handgun application). In contrast, chlorpyrifos failed to reduce S. exitiosa infestations or number of surviving larvae. In most comparisons no effect of nematode application method was detected. In conclusion, our study indicates that S. carpocapsae may be used as an effective “clean-up” measure for S. exitiosa infestations.