Enhancing Natural Enemy Systems: Biocontrol Implementation for Peachtree Borers

Enhancing Natural Enemy Systems: Biocontrol Implementation for Peachtree Borers

Summary

Our overall goal is to tackle the primary remaining challenges to implementing entomopathogenic nematodes as a biocontrol tactic for borer pests, and to assess the broader impact of this biocontrol strategy on the system. We have made substantial progress by 1) implementing our first field experiments to determine optimum method of applying entomopathogenic nematodes for control of peachtree borer, and 2) screening various formulations for toxicity to nematodes and ability to protect nematodes from UV radiation and desiccation. We are on task to achieve our objectives with the end-product being development of a sustainable system for borer control.

Objectives/Performance Targets

Objective I) To determine the optimum method of applying entomopathogenic nematodes (EPNs) for control of peachtree borer (PTB) on a commercial scale.
Objective II) Determine the optimum entomopathogenic nematode formulation for control of LPTB.

Accomplishments/Milestones

Objective I) To determine the optimum method of applying entomopathogenic nematodes (EPNs) for control of peachtree borer (PTB) on a commercial scale.

The primary goal is to determine the optimum method of application for EPN control of PTB; levels of irrigation associated with EPN application will also be tested.

Two field experiments to address Objective 1 were initiated. One experiment was initiated on Lane’s Peach Orchard, Fort Valley, GA. The other test was initiated in Byron, GA on the USDA-ARS research station. The experiment at Lane’s orchard addresses irrigation requirements, whereas the experiment in Byron addresses the method of application. The nematode used in all experiments was Steinernema carpocapsae. The application rate was 1.5 million nematodes per tree.
On Lane’s orchard we applied the following treatments: 1) Nematodes without irrigation, 2) Nematodes with 3 irrigation events per wk, 3) Nematodes without irrigation but with gel applied to protect against desiccation, 4) Lorsban (standard chemical insecticide). There were 4 trees per plot, and each treatment was replicated four times.

At Byron station the following treatments were applied: 1) Nematodes applied by boom sprayer, 2) nematodes applied by handgun, 3) nematodes applied by trunk sprayer, 4) Lorsban, 5) non-treated control, 6) repeated handgun spray but using a different nematode product, 7) in-vivo grown nematodes applied with a watering can (positive control). There were 7 trees per plot and each treatment was replicated three times.

Assessment of PTB damage/infestation to trees will accomplished in April and May 2013.

Objective II) Determine the optimum entomopathogenic nematode formulation for control of LPTB:

Extensive laboratory experiments were conducted to provide initial screening of multiple formulations. From these results we narrow down which formulation(s) to test further under field conditions. Two sets of experiments were conducted. One set of experiments addressed physical properties of the formulations in terms of their ability to withstand UV radiation and desiccation stress. The other set of experiments measured toxicity of the formulations to the nematode, S. carpocapsae.

Several experiments addressed light absorbance (for UV protection) among formulations. The results are indicated in Figs 1-2.

In another experiment, the standard formulation, Barricade gel (shown previously to have promise in field tests), was tested for evaporation rate (weight loss) at different concentrations (Fig. 3).

Lastly, an assessment of toxicity to S. carpocapsae was made using high concentrations of each formulation. The idea was that, if the formulations are not toxic at very high concentrations then there would be no concern for toxicity in the field. All formulations were tested at 5% except OMC, which was at 1%. The viability of nematodes was determined after 2 h in suspension. Results are indicated in Fig. 4.

Those formulations that showed toxicity will be tested at lower concentrations; they may still have utility in field applications depending on the concentration required.

In conclusion: we have made significant progress on the project given the late start (due to delays in funding transfers). In the near future, we will be assessing the PTB applications from the fall, initiating spring PTB applications, and field applications for LPTB. Diversity assessments will also be implemented.

Impacts and Contributions/Outcomes

Based on initial progress we anticipate that novel findings will facilitate the adoption of a sustainable biocontrol solution for peachtree borer control in peaches. The results will also be applicable to other cropping systems.

• Figures for SARE-LS11-241 Annual Report 2012

Collaborators: