Field Suppression of the peachtree borer, Synanthedon exitiosa, using Steinernema carpocapsae: Effects of irrigation, a sprayable gel and application method

Authors: Shapiro Ilan, David; Cottrell, Ted; MIZELL, RUSSELL - University Of Florida; HORTON, DANIEL - University Of Georgia; Abdo, Zaid

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2014
Publication Date: 1/1/2015
Citation: Shapiro Ilan, D.I., Cottrell, T.E., Mizell, R.F., Horton, D.L., Abdo, Z. 2015. Field Suppression of the peachtree borer, Synanthedon exitiosa, using Steinernema carpocapsae: Effects of irrigation, a sprayable gel and application method. Biological Control. 82:7-12.

Interpretive Summary: The peachtree borer, Synanthedon exitiosa, is a major pest of stone fruit trees (such as peaches, plums, cherries) in North America. In previous studies we discovered that a beneficial insect-killing nematode called Steinernema carpocapsae can kill the peachtree borer and prevent infestation in trees. In the previous studies, we applied the nematodes using watering cans. In the present studies we examined two new questions: 1) Can the nematodes be applied effectively using tractors and standard agricultural sprayers? 2) What are the effects of irrigation on nematode efficacy and can a sprayable gel called Barricade be used in lieu of irrigation? The experiments were conducted in peach orchards in Georgia. Our results indicated that application of the beneficial nematodes using a tractor run boom sprayer or trunk sprayer suppressed peachtree borers at the same level as a standard chemical insecticide. Also, our results indicated that nematodes applied without irrigation failed to control the pest. Yet nematodes applied with irrigation, or using the sprayable gel, caused high levels of infestation. Thus, our results indicate that the sprayable gel applied to soil around the tree base can enhance entomopathogenic nematode efficacy, and the gel may be used as a substitute for irrigation when applying nematodes; this finding may be applicable to similar pests in various cropping systems. This is the first report of direct application of the sprayable gel to soil (previous reports concerned aboveground applications). In conclusion, our results demonstrate the ability of beneficial nematodes to control peachtree borer at levels similar to chemical pesticides. Therefore, beneficial nematodes might be used as a natural environmentally friendly biological pest control solution for controlling peachtree borer.

Technical Abstract: The peachtree borer, Synanthedon exitiosa, is a major pest of stone fruit trees in North America. In prior studies, the entomopathogenic nematode, S. carpocapsae, caused substantial reductions in S. exitiosa damage when applied by watering can to peach trees that were irrigated regularly. Here we report two additional studies: one study focused on irrigation requirements and the other on application method. In both experiments chlorpyrifos was also included as a positive control, and in the application methods experiment an untreated (negative) control was also included. All treatments were applied in the fall of 2012 and 2013 and S. exitiosa infestation was assessed following the spring of 2013 and 2014, respectively. In the first experiment, nematodes applied without irrigation did not prevent high levels of infestation levels (75% of trees were infested) whereas nematodes applied with the sprayable gel suppressed damage at the same level as chlorpyrifos (< 20% infestation). Thus, our results indicate that the sprayable gel applied to soil around the tree base can enhance entomopathogenic nematode efficacy, and the gel may be used as a substitute for irrigation when applying S. carpocapsae for S. exitiosa control; this finding may be applicable to similar pests in various cropping systems. This is the first report of direct application of the sprayable gel to soil (previous reports concerned aboveground applications). Also in the first experiment, intermediate levels of damage (31-38% infestation) were observed in plots that received nematodes with irrigation. We suspect that a higher rate of irrigation would have improved efficacy. In the second experiment, the boom sprayer, trunk sprayer and watering can methods of nematode application resulted in S. exitiosa infestations that were similar to the chemical insecticide standard treatment (chlorpyrifos) and below levels in the non-treated control, whereas the handgun treatment was not different from the untreated control or chemical standard.