ENHANCING THE BIOLOGICAL CONTROL POTENTIAL OF ENTOMOPATHOGENIC NEMATODES PROTECTION FROM DESICCATION AND UV RADIATION

Abstract

Entomopathogenic nematodes (EPNs) are obligate parasites of insects. EPNs have a broad host range, are easily mass reared, and kill insects within 48 hours. EPNs are safe for vertebrates, plants, and non-target organism. On the other hand, EPNs have disadvantages that make them less effective against foliar insect pest because they are sensitive to desiccation, ultraviolet (UV) radiation and high temperatures. The goal of this research was to improve the efficacy of aboveground application EPNs by protecting them against desiccation and UV radiation. The first objective was to determine efficacy of the desiccation protectant Barricade gel in extending the viability of EPNs. The second objective was to evaluate the effect of UV chemical protectants on EPNs viability. The third objective was to demonstrate enhanced insect control with EPNs protected from UV radiation and desiccation. Barricade® is a proprietary fire-protection product that prevents desiccation. Barricade® gel toxicity to Steinername feltiae and mealworm (Tenebrio molitor) was determined in laboratory experiments. Subsequently, the effect of Barricade® gel on IJ infectivity was determined at different (0, 1, 1.5, 2, 3, and 4%) concentration. Barricade® gel was not toxic to mealworm larvae nor the IJ of S. feltiae. IJ survival was enhanced by Barricade® gel and Barricade® gel prevented desiccation of IJs allowing for greater IJ infection and mealworm larvae mortality. In an excised leaf experiment, Barricade® application enhanced IJ infection of the mealworm larvae over time compared to application in water alone. EPNs and mealworm larvae were exposed to UV radiation protectant chemicals P-amino benzoic acid (PABA) and octyl methoxycinnamate (OMC), Congo red, titanium dioxide, and zinc oxide were not toxic to mealworm larvae and EPNs. PABA, OMC, Congo red, titanium dioxide, and zinc oxide protected IJ from exposure to UV light for 0, 4, 8 and 12 hrs. After 48 hrs exposure, PABA afforded the greatest protection to EPN compared to other chemicals. OMC provided the second greatest protection to EPN compared to other chemicals. The UV protectants PABA and OMC were individually combined with Barricade® fire gel and IJs were added. The IJs were exposed to full spectrum UV light in the laboratory for up to 12 hrs. The subsequent number of dead mealworm larvae was greatest in the combination treatments of OMC+Barricade and PABA+Barricade. These treatments afforded the greatest protection to IJs from UV radiation and desiccation in a filter paper experiment and a choy sum (Brassica chinensis var. parachinensis) leaf assay. The survival of IJ can be enhanced when applied with a desiccant protectant such as Barricade and a chemical such as PABA or OMC to protect against UV radiation. The protection afforded to the IJ by these chemicals allows for greater infection and mortality of target insect pests. The formulation of IJs with desiccant and UV radiation protection will allow the greater use of EPN for the management of foliar insect pests.