Susceptibility of Japanese Beetle Larvae to Bacillus popilliae

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Abstract
Laboratory studies on the numerical relationship of spores of Bac. popilliae to the incidence of milky disease among Japanese beetle (Popillia japonica) larvae demonstrated that the incidence of disease is a probit response to the logarithm of the conc. of spores, not only when injd. parenterally, but when present in soil in which the grubs are reared. As judged by these 2 modes of infection, the virulence of Bac popilliae in causing milky disease of Japanese beetle larvae is far less than that of Bac larvae in causing foul brood of honeybee larvae. Spores of Bac popilliae injected into the alimentary tract of beetle grubs do not demonstrate a well-defined dosage effect, and the incidence of disease is less than expected. Evidence is presented that resistance of grubs and reduced potency of bacterial spores may act independently to cause less disease than expected.