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United States Department of Agriculture

Agricultural Research Service

Title: Virulence of Metarhizium Anisopiae in Sugarbeet Root Maggot Larvae

Authors
item Jonason, Nyle
item Botel, Mark - ND STATE UNIVERSITY
item Eide, John
item Campbell, Larry
item Roa, M - ND STATE UNIVERSITY

Submitted to: Journal of Sugarbeet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 6, 2005
Publication Date: December 1, 2005
Citation: Jonason, N.B., Boetel, M.A., Eide, J.D., Campbell, L.G., Rao, M.B. 2005. Virulence of Metarhizium anisopiae (Deuteromycotina: Hyphomycetes) to sugarbeet root maggot (Diptera: Ulidiidae) larvae. Journal of Sugarbeet Research. 42(3&4):103-117.

Interpretive Summary: Sugarbeet root maggot is the major insect pest of sugarbeet in the U.S.A. It is ususally controlled by applying one of two chemical insecticides. These chemical could be removed from the market or the root maggot could develop resistance to the insecticides. An effective biological control agent would provide an alternative control measure. Laboratory bioassays and survival probability analyses were used to estimate virulence of the entomopathogenic fungus, Metarhizium anisopliae to root maggot larvae. Higher (>106 conidia/ml) dosages consistently caused significant larval mortality when compared with the controls, and rate responses were evident. The results of this study demonstrate that M. anisopliae is a virulent fungal pathogen of sugarbeet root maggot larvae. This work also establishes a virulence baseline for M. anisopliae and for other entomopathogenic fungi as potential organisms for bio-based management of the root maggot. More research will be necessary to develop appropriate formulations, application methodology, and treatment timing to optimize the efficacy of this entomopathogen for controlling this important insect pest of sugarbeet.

Technical Abstract: Laboratory bioassays and survival probability analyses were used to estimate virulence and to establish lethal time (LT50) values for the entomopathogenic fungus, Metarhizium anisopliae (Metschnikoff) Sorokin to third-instar Tetanops myopaeformis Röder. Higher (>106 conidia/ml) dosages consistently caused significant larval mortality when compared with the controls, and rate responses were evident in both bioassays. In bioassay I, the LT50 values for 106, 107, and 108 conidia/ml were 16, 10, and 7 days after exposure (DAE), respectively. Similarly, respective LT50 values for the 106, 107, and 108 conidia concentrations were 15, 9, and 7.5 DAE in bioassay II. Survival likelihood at 12 DAE was 0% for larvae treated with 108 M. anisopliae conidia and <15% after exposure to the 107 concentration. All of the lower (<105 conidia/ml) concentrations of the pathogen failed to achieve 50% larval mortality and, thus, would not be likely to cause sufficient mortality under field conditions. The results of this study demonstrate that M. anisopliae is a virulent fungal pathogen of T. myopaeformis larvae. This work also establishes a virulence baseline for M. anisopliae and for other entomopathogenic fungi as potential organisms for bio-based management of T. myopaeformis. More research will be necessary to develop appropriate formulations, application methodology, and treatment timing to optimize the efficacy of this entomopathogen for controlling this important insect pest of sugarbeet. Additional work should also be aimed at screening more M. anisopliae isolates and other entomopathogenic fungi to identify the most virulent organism for use against T. myopaeformis.

Last Modified: 9/22/2014
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