Using the nematode, Steinernema Carpocapsae to control peachtree borer (Synanthedon Exitiosa): Optimization of application rates and secondary benefits in control of root-feeding weevils

Authors: Wong, Colin; Shapiro Ilan, David; Hofman, Camila; BLAAUW, BRETT - University Of Georgia; CHAVEZ, DARIO - University Of Georgia; JAGDALE, GANPATI - University Of Georgia; MIZELL, RUSS - University Of Georgia

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2022
Publication Date: 11/10/2022
Citation: Wong, C.R., Shapiro Ilan, D.I., Hofman, C.O., Blaauw, B., Chavez, D., Jagdale, G., Mizell, R. 2022. Using the nematode, Steinernema Carpocapsae to control peachtree borer (Synanthedon Exitiosa): Optimization of application rates and secondary benefits in control of root-feeding weevils. Agronomy Journal. 12:2689. https://doi.org/10.3390/agronomy12112689.
DOI: https://doi.org/10.3390/agronomy12112689

Interpretive Summary: Peach trees in an orchard setting are subject to attack from a number of insect pests. The peachtree borer is a moth, the larvae of which will bore into the roots of peach trees causing damage. A number of weevils (beetles) also share this behavior, but cause less damage on average and are therefore referred to as secondary pests. We explored the use of natural enemies of these insect pests, entomopathogenic nematodes, to control the pest in an environmentally sound manner. Entomopathogenic nematodes are a type of near microscopic round worm that will infect and kill insects, and are naturally found in the soil. We found that deploying commercially available entomopathogenic nematodes around the base of peach trees and covering them with a gel to hold the moisture in the soil helped to control the insect pests. Damage from the peachtree borer moth larvae was reduced, and the number of weevils that survived to adulthood was also reduced. We varied the amounts of nematodes used and the amount of cover gel used. We found that the treatments were still effective using one third the amount of nematodes as in previous research and half the concentration of gel used in previous research. This research supports that entomopathogenic nematodes could be used as a cost effective tactic to reduce damage from insect pests in peach orchards.

Technical Abstract: The peachtree borer, Synanthedon exitiosa (Say) (Lepidoptera: Sesiidae), is a major pest of stone fruits including peach Prunus persica (L.) Batsch. The entomopathogenic nematode, Steinernema carpocapsae, was previously shown to be an effective tool for controlling S. exitiosa. In orchards where irrigation is not available, a sprayable gel (Barricade®) can be used to maintain soil moisture that can facilitate nematode efficacy. However, rates of nematode and Barricade® application had not been optimized for their maximum economic and biocontrol efficiency. Therefore, our objective was to compare rates of S. carpocapsae and Barricade in field trials. Nematodes were tested at rates of 1.5 million, 1 million and 0.5 million infective juveniles per tree. The sprayable gel was used at two rates, 4% (full rate on the label) and 2%. A reduction of the nematodes used from 1.5 million to 0.5 million per tree showed no difference in efficacy. Similarly, using the gel at half rate also did not impact the efficacy and treatments containing nematodes controlled the S. exitiosa better than the chlorpyrifos control in several of the tests (P < 0.05). As an added benefit, the nematode treatments were also able to reduce the prevalence of weevil (Coleoptera: Curculionidae) populations as secondary pests of the peach trees. With lower rates of grower inputs being required this form of biocontrol will be more feasible to be adopted by commercial growers of peach.