Reduction of grasshopper populations following field application of the fungus Beauveria bassiana.
Conidia of Beauveria bassiana were applied in an attempt to reduce field populations of grasshoppers, primarily Melanoplus sanguinipes with lesser numbers of M. bivittatus, M. infantilis, M. packardii and Camnula pellucida, in Alberta, Canada, in 1991. Dry spores were applied with wheat bran carrier to 3 fallow fields at a rate of 2.0 × 1013 spores/ha in 10 kg bait/ha. Examination of culture plates that had been placed in the field to capture spores and of bran carrier with scanning electron microscopy indicated that a substantial portion of the B. bassiana colony-forming units (spores and clumps of spores) did not adhere to the bran and were applied in the field as free particles. Acridids collected from the treated plots at intervals after application were assayed for infection by B. bassiana. The observed rate of mycosis in the treated populations was 70% of those collected after 2 days, declining to 41% by 13 days and 5% by 19 days after application. Analysis of reductions in population density gave results in agreement with the infection data. Treated populations declined 60% and 33% by 9 and 15 days after application, resp.