Novel pest management using bacterial metabolites in pecan

Pesticide regulations, as well as resistance development, have limited the pest management options of pecan growers. Although biocontrol strategies, such as entomopathogenic nematodes in the Heterorhabditidae and Steinernematidae families, can be effective, their efficacy is subject to environmental factors such as desiccation and UV radiation. Culture broths of the symbiotic bacteria (Photorhabdus spp. and Xenorhabdus spp., respectively) cultivated by these nematodes previously demonstrated insecticidal activity against two species of pecan aphids (Monellia caryella and Melanocallis caryaefoliae) in the laboratory. However, in preliminary field tests the bacterial broths were not potent enough to significantly lower aphid populations. The goal of this study is to test the pesticidal potential of the metabolite extractions of these bacteria, via laboratory and field tests against M. caryella and M. caryaefoliae. For the laboratory tests, aphid nymphs will be caged on water agar plates containing pecan leaf discs, and both the aphids and leaf discs will be treated with various dilutions of the metabolite extracts of each bacterium as well as undiluted culture broths of these same bacteria. The field tests will utilize natural aphid populations in pecan orchards, and treatments of the metabolite extracts will be compared to bacterial culture broths and a standard insecticide. The metabolites are expected to significantly suppress the aphid populations and may potentially serve as novel pest management strategies in the pecan industry.