Effect of the bacterium Yersinia entomophaga on adult bronze beetle

Abstract

The entomopathogenic bacterium Yersinia entomophaga MH96 (Ye MH96) was produced by aerobic fermentation and applied in laboratory and field bioassays to control bronze beetle (Eucolaspis sp.). In the laboratory, bacteria were applied to apple leaves at a range of cell densities using a Potter Tower. After 6 days of exposure, the LC50 of fieldcollected beetles was calculated as approximately 5.0×106 cells/cm2 of leaf surface with high concentrations killing all treated adults. Time to death was inversely correlated with dose rate with the LT50 at the highest dose being 3.6 days. Marked apple shoots were sprayed in the field, each shoot enclosed in a sleeve cage and healthy beetles added. After 7 days, beetle mortality averaged 42% following a single application and 66% after multiple treatments. Leaf damage was reduced by bacterial application. The results show that Ye MH96 has potential for development as a biopesticide against this intractable pest of organic apple production.