Exchange of Inoculum of Beauveria bassiana (Bals.) Vuill. (Hyphomycetes) Between Adult Flies of the Cabbage Maggot Delia radicum L. (Diptera: Anthomyiidae)

Adult cabbage maggots (Delia radicum L.) were exposed to dry conidia of isolates of several hyphomycetous fungi by placing them in a centrifuge tube containing conidia, then releasing them into small screened plastic cages. Mortality was assessed after 48, 120 and 160 h. A Beauveria bassiana isolate (P89 from Musca domestica) caused the highest mortality after 48 h, resulting in 100% mortality and 100% infection. Isolate L90 (B. bassiana) and one Metarhizium anisopliae isolate (ARSEF 2521) also caused fatal infection in more than 50% of the Xies. To investigate exchange of inoculum, Xies were placed in a small container with a dry powder formulation containing B. bassiana (Mycotrol ) on the bottom. The Xies were removed to small screened cages containing untreated Xies. This experiment conWrmed the ability of Xies to pass inoculum to other Xies. In a similar experiment, one treated Xy was placed in each cage with one untreated Xy. When each Xy died, one untreated Xy was added to each cage after the dead Xy was removed. This study showed that Xy to Xy transfer of fatal doses of inoculum was possible for a series of at least six Xies. When female Xies were exposed to the inoculum, then transferred to small cages containing males and an oviposition substrate, no eggs were laid. Further studies are being conducted to develop a system where Xies attracted to a trap will be inoculated with the fungus and spread it to a Weld population.