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United States Department of Agriculture

Agricultural Research Service

Research Project: ECOLOGY AND MANAGEMENT OF GRASSHOPPERS AND OTHER INSECT PESTS IN THE NORTHERN GREAT PLAINS Title: It’s a Jungle Out There! Abiotic and Biotic Factors That Affect Efficacy and Persistence of the Entomopathogenic Fungi

Author
item Jaronski, Stefan

Submitted to: Society for Invertebrate Pathology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2009
Publication Date: N/A

Interpretive Summary: One might conclude the soil is a more congenial arena for using entomopathogenic fungi (EPF) than the phylloplane. No ultraviolet light, no rainfall washing conidia from foliage, no rapid attenuation of conidial deposits by rapid plant canopy expansion. The soil is cool, damp and dark – perfect for EPF yes?. In reality, “It’s a jungle out there!” wherein ignorance (of the many factors that affect both fungal efficacy and persistence) can tempt one into (fatal) bliss. This presentation will summarize what we do and do not know about factors that can affect the successful outcome of using fungal pest control agents against soil insects. The effect of some factors are better known (e.g., microbial soil flora), or more obvious (e.g., temperature). Other factors are still poorly understood. One case in point is the interaction between soil texture, moisture, and insect behavior on the infectivity of individual conidia in soil. Soil texture can significantly affect the infectivity of conidia, as can the moisture content of the soil. But life is not that simple. In the case of larval Diabrotica increasing soil moisture decreases efficacy of Beauveria conidia. In the case of sugarbeet root maggot and Metarhizium. The reverse seems to be true. Use of granules can change the rules of the game substantially. While recent data indicate Metarhizium may colonize the rhizosphere, this phenomenon may not be as common as we think and the rhizosphere contains many microbes that can be antagonists of the EPF. Little is known about these microbe-fungus interactions. Very little is known about the interaction between soil macrofauna and EPF conidia. Collembola may not be susceptible to EPF but can they affect conidial titers as strongly as they do plant pathogenic fungi? What about mites and other fauna? What about soil dwelling Protista?

Technical Abstract: One might conclude the soil is a more congenial arena for using entomopathogenic fungi (EPF) than the phylloplane. No ultraviolet light, no rainfall washing conidia from foliage, no rapid attenuation of conidial deposits by rapid plant canopy expansion. The soil is cool, damp and dark – perfect for EPF yes?. In reality, “It’s a jungle out there!” wherein ignorance (of the many factors that affect both fungal efficacy and persistence) can tempt one into (fatal) bliss. This presentation will summarize what we do and do not know about factors that can affect the successful outcome of using fungal pest control agents against soil insects. The effect of some factors are better known (e.g., microbial soil flora), or more obvious (e.g., temperature). Other factors are still poorly understood. One case in point is the interaction between soil texture, moisture, and insect behavior on the infectivity of individual conidia in soil. Soil texture can significantly affect the infectivity of conidia, as can the moisture content of the soil. But life is not that simple. In the case of larval Diabrotica increasing soil moisture decreases efficacy of Beauveria conidia. In the case of sugarbeet root maggot and Metarhizium. The reverse seems to be true. Use of granules can change the rules of the game substantially. While recent data indicate Metarhizium may colonize the rhizosphere, this phenomenon may not be as common as we think and the rhizosphere contains many microbes that can be antagonists of the EPF. Little is known about these microbe-fungus interactions. Very little is known about the interaction between soil macrofauna and EPF conidia. Collembola may not be susceptible to EPF but can they affect conidial titers as strongly as they do plant pathogenic fungi? What about mites and other fauna? What about soil dwelling Protista?

Last Modified: 12/18/2014
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