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Funded Project

Funding Program: Regional IPM Grants (S-RIPM)

Project Title: Development of Improved Monitoring Techniques and Decision Tools for the Dogwood Borer, Synanthedon scitula Harris, in Southern Apple Orchards

Project Director (PD): J. Christopher Bergh [1]

Lead State: VA Lead Organization: Virginia Polytechnic Institute & State University

Research Funding: $80,425

Start Date: Aug-01-2003 End Date: Jul-31-2005

Summary: None provided Objectives: None provided

Final Report:

Results PROGRESS: 2003/08 TO 2006/07 This proposal contained three main objectives. The primary goal of Objective 1 was to identify the sex pheromone of the female dogwood borer (DWB). Our identification of a trinary (3-component) blend of pheromone components resulted in a tremendous increase in the number of male DWB captured in commercial apple orchards. The trinary blend was significantly more attractive (up to 364X) than the best commercially available pheromone lure and was much more species-specific than commercial lures (i.e. it attracted very few other species of clearwing moth). Traps baited with the trinary blend captured many more males than traps baited with virgin female DWB. Another major finding was that a geometrical isomer of the main pheromone component is a strong behavioral antagonist. Addition of as little as 0.5% of this isomer to the trinary blend virtually eliminated the response of male DWB to its sex pheromone. In Objective 2, we used the new pheromone blend to monitor the flight activity of DWB in commercial apple orchards, revealing that seasonal trap captures show at least two peaks, although weekly captures remain relatively high from late May through late September. Our preliminary data on the development of larvae on burr knot tissue on potted apple trees suggest that larvae can complete development on that food source in about 50-60 days. In contrast with earlier conclusions, this finding suggests that there are at least two, and possibly multiple generations of DWB on apple in the Mid-Atlantic region. This may partially explain the large numbers of moths captured in apple orchards. The goal of Objective 3 was to assess the ability of a refined, pheromone-based monitoring strategy to predict infestation levels in apple. We were not able to develop a relationship between trap captures and larval infestation levels, due primarily to the likelihood that larvae infest not only burr knots at the base of trees, but also numerous areas on the trunk and branches of mature apple trees. This made accurate weekly counts and collections of fresh pupal exuviae virtually impossible. Given that these pupal exuviae counts were to provide the independent variable upon which this model was to be based, the development of the relationship was not feasible. In summary, the research supported by this award has resulted in major improvements in our understanding of the biology and ecology of DWB and in our ability to measure its true abundance in different habitats. Our data have revealed that it far more abundant than was previously known and have provided preliminary insights as to why this is so. In combination with the results from our other studies on DWB, we conclude that this pest is probably not affecting the vigor and productivity of mature apple trees in a significant way. However, DWB definitely poses a significant risk to the growth and establishment of young apple orchards planted on size-controlling rootstocks. Patent: Female Sex Pheromone of the Dogwood Borer (DWB), Synanthedon scitula, and Attraction Inhibitor (Antagonist). Patent # 05.023. US Utility application filed March 9, 2006. Issuance pending. IMPACT: 2003/08 TO 2006/07 Our identification of the dogwood borer sex pheromone has provided a highly sensitive monitoring tool for this pest. Use of this pheromone in commercial apple orchards has revealed that dogwood borer is much more abundant and widespread than was previously understood, and our data underscore the need for growers to be more aware of this pest, particularly during the early years of establishment of new orchards planted on size-controlling rootstocks. In addition to being more attractive to dogwood borer males than virgin female dogwood borer (based on the numbers of moths captured), the new pheromone blend is much more species-specific (i.e. selective) for dogwood borer, attracting many fewer clearwing moths of other species than did previous formulations. The sensitivity, species-specificity and attractiveness of the new pheromone is critical for developing and evaluating new, behaviorally-based management tactics for dogwood borer, such as mass-trapping, attract-and-kill or mating disruption. Our data on the abundance of this pest and its potential for multiple generations in the apple ecosystem, validate exploration of new management approaches, particularly in light of increasing restrictions on the use of the organophosphate pesticides which have been the most effective management tools. PUBLICATIONS (not previously reported): 2003/08 TO 2006/07 1. Leskey, T.C., J.C. Bergh, J.F. Walgenbach and A. Zhang. 2006. Improved attractiveness and specificity of pheromone-baited traps for male dogwood borer, Synanthedon scitula Harris (Lepidoptera: Sesiidae). Environ. Entomol. 35: 268-275 2. Bergh, J.C., T.C. Leskey, J.M. Sousa and A. Zhang. 2006. Diel periodicity of emergence and pre-mating reproductive behaviors of adult dogwood borer (Lepidoptera: Sesiidae). Environ. Entomol. 35: 435-442 3. Zhang, A., T.C. Leskey, J.C. Bergh and J.F. Walgenbach. 2005. Sex pheromone of the dogwood borer (DWB), Synanthedon scitula. J. Chem. Ecol. 31: 2463-2479 4. Bergh, J.C., T.C. Leskey and A. Zhang. 2004. Discrimination by male dogwood borer, Synanthedon scitula (Lepidoptera: Sesiidae) among traps baited with commercially available pheromone lures. J. Econ. Entomol. 97: 344-352 5. Bergh, J.C. and T.C. Leskey. 2003. Biology, ecology and management of dogwood borer in eastern apple orchards. Can. Entomol. 135: 615-635

Outcomes N/A

Impacts From Report submitted by the PI to USDA CRIS report system Our identification of the dogwood borer sex pheromone has provided a highly sensitive monitoring tool for this pest. Use of this pheromone in commercial apple orchards has revealed that dogwood borer is much more abundant and widespread than was previously understood, and our data underscore the need for growers to be more aware of this pest, particularly during the early years of establishment of new orchards planted on size-controlling rootstocks. In addition to being more attractive to dogwood borer males than virgin female dogwood borer (based on the numbers of moths captured), the new pheromone blend is much more species-specific (i.e. selective) for dogwood borer, attracting many fewer clearwing moths of other species than did previous formulations. The sensitivity, species-specificity and attractiveness of the new pheromone is critical for developing and evaluating new, behaviorally-based management tactics for dogwood borer, such as mass-trapping, attract-and-kill or mating disruption. Our data on the abundance of this pest and its potential for multiple generations in the apple ecosystem, validate exploration of new management approaches, particularly in light of increasing restrictions on the use of the organophosphate pesticides which have been the most effective management tools.

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