Submitted to: Biocontrol Science and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/2/2000
Publication Date: N/A
Citation: Interpretive Summary: The cabbage maggot fly is a key pest of crucifers grown in the Northern Hemisphere. Available insecticides are limited to organophosphate compounds that soon will be unavailable, and safe, effective alternatives for fly management must be found. Spores of the fungus Beauveria bassiana serve as the active ingredient in a microbial insecticide formulated for use against this and other insects. In order to use this fungus, or related fungi, effectively in the field, a basic understanding of factors influencing fungal infection of flies must be developed. In this laboratory study, untreated flies readily became infected when placed in cages with individual fungus-inoculated flies. Fly-to-fly transfer of fatal doses of inoculum was possible for a series of six pairs of flies. Furthermore, inoculated female flies were unable to lay eggs. These results indicate the potential for fly-to-fly transmission of fungal inocula in the field. Field studies are aimed at development of attractan traps in which flies will be inoculated with fungal spores.
Technical Abstract: Adult cabbage maggots, Delia radicum, were exposed to dry conidia of isolates of several Hyphomycetes fungi and then released into small cages. Mortality was assessed after 48, 120 and 160h. A Beauveria bassiana isolate (P89 from Musca domestica) caused the highest mortality after 48h. The same isolate caused 100% mortality and 100% infection. Isolate L90 (B. .bassiana) and one Metarhizium anisopliae isolate (ARS 2521) also caused fatal infection in more than 50% of the flies. Flies placed in cages with untreated flies successfully passed inoculum to other flies. In a similar experiment, one treated fly was placed in each cage with one untreated fly. When each fly died, one untreated fly was added to each cage after the dead fly was removed. Fly-to-fly transfer of fatal doses of inoculum was possible for a series of at least six flies. When female flies 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 flies attracted to a trap will be inoculated with the fungus and spread it to a field population.