Pathogenicity of Beauveria bassiana to adult Diaprepes abbreviatus

The Diaprepes root weevil (DRW) is a serious insect pest in the state of Florida. It causes an estimated {dollar}75 million in damages every year to Florida's citrus industry. Attempts at chemical control of this pest are costly with limited effectiveness. The use of Beauveria bassiana , a common native entomopathogen as a biological control agent of Diaprepes abbreviatus could reduce pesticide usage in controlling this pest. A commercially produced dry powder formulation of Beauveria bassiana was used in this research to determine its affect on weevil adults. Conidia of Beauveria bassiana were found to germinate on the weevil exoskeleton at various rates depending on the body region. Conidia located in inter-segmental areas of the abdomen and head germinated at twelve hours post-inoculation; on other areas of the abdomen, germination was first observed eighteen hours post-inoculation. Germination on the elytra occurred 30 hours post-inoculation and even then, germination was low. Internal ramification of hyphal bodies began to appear 72 hours post-inoculation. The time between cuticle penetration and the development of hyphal bodies in the hemolymph appeared to be delayed by an immune response of the hemocytes. Internal proliferation of hyphae rapidly consumed the insect body cavity causing death after as few as 6 days. Sporulation on the cadaver usually occurred two to three days after death under moist conditions. Diaprepes root weevils interact by touching in the wild. This touching is not limited to sexual contact, inter-sexual touching also occurs and is possibly a form of communication. Weevils transmitted conidia through both bisexual and same sex contact. Adult mortality from this contact was not significantly different between sexes. These data suggest that adult weevils can spread fungal conidia within a native population.