FORMULATION OF THE ENTOMOPATHOGENIC FUNGUS,BEAUVERIA BASSIANA, WITH RESISTANCE TO UV DEGRADATIONFOR CONTROL OF TARNISHED PLANT BUG, LYGUS LINEOLARIS

摘要

Formulations are being developed for protecting entomopathogenic fungi from solar radiation to improve mycoinsecticideefficacy. Beauveria bassiana (GHA) spores were coated by spray drying with either water-soluble lignin or water-insolubleCa2+-cross-linked lignin. These coated spores were suspended in either water (0.04% Silwet L77) or oil (Orchex 692) andcompared with non-coated spores in water or oil to demonstrate the impact of the coating on spore survival under simulatedsolar radiation and pathogenicity to tarnished plant bug, Lygus lineolaris (Palisot de Beauvois). The rate of spore mortalityunder simulated solar radiation was approximately ten times lower for the three formulations in which spores in suspensionremained coated with lignin (cross-linked lignin in water, lignin in oil, and cross-linked lignin in oil). The pathogenicity ofthe six formulation strategies did not differ significantly on the basis of LC50 values for direct spray applications to L lineolarisadults. However, the three lignin coated formulations that provided the greatest UV protection were slower to kill L.lineolaris (higher LT50 values). Adult L. lineolaris mortality was approximately 20 times lower when exposed to broccoli floretstreated with B. bassiana formulations than when L. lineolaris was sprayed directly. In bioassays with treated broccoli florets,non-coated spores in 0.04% Silwet L77 were the most pathogenic. Under field conditions where solar radiation significantlyimpacts mycoinsecticide efficacy, the improved persistence of lignin coating formulations may outweigh the negativeeffects of reduced pathogenicity.