CHEMICAL CONTROL OF GLASSY-WINGED SHARPSHOOTER: ESTABLISHMENT OF BASELINE TOXICITY AND DEVELOPMENT OF MONITORING TECHNIQUES FOR DETECTION OF EARLY RESISTANCE TO INSECTICIDES

• Author(s): Castle, Steven; Toscano, Nilima;
• Abstract: The possibility of resistance development when insecticides are used necessitates the development of an effective resistancemonitoring program that enables early detection of even low-frequency resistance alleles in natural populations. The initial step for monitoring of resistance is through development of appropriate bioassay techniques that can establish baseline susceptibility data among populations. Our goal for the first year was to study the effectiveness of selected insecticides that represent various chemistries against GWSS and determine regional comparisons of GWSS responses to these insecticides. Simple and suitable bioassay techniques were developed to detect toxicological responses and to establish baseline susceptibility data of GWSS to various insecticides. Three techniques, petri-dish, leaf-dip and systemic bioassays were described in the previous report (Toscano et al. 2001). Evaluation continued during the second season to assess any changes in responses of GWSS to a wide range of chemistry. The present report compares the toxicological responses of GWSS for a period of two years. Resistance does not evolve at the same rate for all pests that come under selection pressure. Many factors influence the rate at which resistance develops in a pest. In the case of GWSS, we have no information on the potential for resistance development in this species. One method to estimate the potential for resistance risk is to artificially select resistant strains under greenhouse conditions. In addition to conventional bioassay methods, we have completed our development of a biochemical assay that measures the levels of sensitivity of sharpshooter acetylcholinesterases (AChEs) to inhibition by organophosphate (OP) insecticides. Insensitivity of the AChE target-site can seriously impair the effectiveness of the OPs in control programs. The assay can be used on all nymphal instars and adults, and is an excellent tool for monitoring the frequencies of AChE variants in populations because it provides inhibition data for individual insects. Monitoring populations of GWSS and smoke-tree sharpshooter that have been exposed, either directly or indirectly, to OPs such as chlorpyrifos will enable us to detect resistant AChE alleles should they arise.
• Publication Date: Dec 2002
• Journal: 2002 Pierce's Disease Research Symposium