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ARS Home » Midwest Area » Wooster, Ohio » Application Technology Research » Research » Publications at this Location » Publication #78795
Title: MORTALITY INDUCED BY VACILLUS POPILLIAE IN CYCLOCEPHPALA (COLEOPTERA: SCARABAEIDAE) HELD UNDER SIMULATED FIELD TEMPERATURES

Author
item CHERRY, R - UNIV FLORIDA
item Klein, Michael

Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: White grubs of the family Scarabaeidae are important pests of agricultural and horticultural plants, and turf world wide. The bacterium Bacillus popilliae causes milky disease in many of these scarabs and is one of the most widely known insect pathogens. Prevalence of a disease is one of the most commonly used parameters in epizootiology and is defined as the number rof hosts afflicted with that disease at a given time. However, we felt that since the death of milky grubs removes them from the population, prevalence data underestimate the cumulative mortality, particularly in warm climates where infected grubs may die quickly. We observed mortality caused by milky disease bacteria in naturally infected grubs of Cyclocephala parallela held under simulated field temperatures and found that infected grubs did die six to eight times more quickly than those uninfected. This demonstrates that prevalence of the disease at any one time seriously underestimates the value of milky disease in population suppression. Scientists and growers alike will use this research result when making management decisions.

Technical Abstract: The bacterium, Bacillus popilliae Dutky, causes milky disease in numerous species of scarabs around the world. Bacillus popilliae induced mortality in naturally infected grubs (third instars) of Cyclocephala parallela Casey was measured when held under simulated field temperatures. Our data show that visual examination in the field underestimates the percentage of grubs actually infected by B. popilliae. 5.6 to 8.2 times as many milky disease infected grubs died during the first 60 days of incubation under simulated field temperatures than did uninfected grubs. These data show that the widely used prevalence value underestimates the total mortality which this bacterium ultimately causes to C. parallela.