The use of fungal entomopathogens as endophytes in biological control: a review

ABSTRACT

Fungal entomopathogens have been proposed as environmentally friendly alternatives to chemical control. Unfortunately, their effectiveness continues to be limited by their susceptibility to ultraviolet (UV) light and low moisture. A relatively recent development, the use of fungal entomopathogens as endophytes, might overcome the traditional obstacles impeding the widespread adoption of fungal entomopathogens and also provide a novel alternative for management of insect pests and plant pathogens. In addition, some fungal entomopathogens could also function as biofertilizers. Eighty-five papers covering 109 individual fungal entomopathogen studies involving 12 species in six genera are reviewed. Thirty-eight plant species in 19 families were studied, with maize, common bean, and tomato being the most investigated. Of the 85 papers, 39 (46%) examined the effects of fungal entomopathogen endophytism on 33 insect species in 17 families and eight orders. Thirty-four (40%) examined plant response to endophytism, corresponding to 20 plant species. Various inoculation techniques (e.g., foliar sprays, soil drenching, seed soaking, injections, etc.) are effective in introducing fungal entomopathogens as endophytes, but colonization appears to be localized and ephemeral. The field of insect pathology will not substantially profit from dozens of additional studies attempting to introduce fungal entomopathogens into a wider array of plants, without attempting to understand the mechanisms underlying endophytism, the responses of the plant to such endophytism, and the consequent responses of insect pests and plant pathogens. This review presents several areas that should receive focused attention to increase the probability of success for making this technology an effective alternative to chemical control.

KEYWORDS:

• Beauveria
• endophytic
• entomopathogenic fungi
• Metarhizium

ACKNOWLEDGMENTS

The author expresses his appreciation to Gerald Bills, Meredith Blackwell, George Carroll, Keith Clay, Stan Faeth, Melinda Greenfield, Rich Humber, Mark Jackson, Harry Kaya, Xinggang Liao, Wayne Olson, Enrique Quesada-Moraga, Scott Redhead, Stefan Vidal, and Jim White for their generous help with questions related to the topics covered in this paper. Comments by Gerald Bills, Harry Kaya, Keith A. Seifert, and Ann Simpkins on a previous version of the manuscript are greatly appreciated. The author thanks especially Joey Spatafora, Cathie Aime, and Ning Zhang for the invitation to contribute to this special issue. This review is dedicated to Meredith Blackwell in celebration of her outstanding contributions to mycology.

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