Acquisition, retention and dispersal of soilborne plant pathogenic fungi by fungus gnats and moth flies

Abstract

AbstractAdult fungus gnats and moth flies were experimentally demonstrated to function as potential above‐ground vectors for three soilborne plant pathogens: Verticillium dahliae, Fusarium acuminatum and Thielaviopsis basicola. The adult insects externally acquired the conidia of the pathogens after exposure to the cultures as confirmed by scanning electron microscope photography. The intestinal contents and frass deposits of larvae exposed to fungal cultures contained viable fungal propagules. Internally infested larvae developed into internally infested pupae; however, the emerging adults were free of fungal structures. Because of the maintenance of a high level of inoculum on the external body surface and the ability of these adult insects to fly, they can be a significant factor in the dispersal of soilborne fungi in greenhouse agriculture. The rate of dispersal of T. basicola by adult fungus gnats was 1.78 cm2 h−1 per insect and by adult moth flies was 1.17 cm2 h−1 per insect. The area over which the pathogen was dispersed by the adult insects increased with the increase in exposure time. The study demonstrated that adult insects are efficient distributors of soilborne plant pathogenic fungal propagules.