Field and Laboratory Investigations with Entomophthora fresenii, a Pathogen of Tetranychus Spp.1

Abstract

A pathogenic fungus, Entomophthora fresenii Nowakowski, was found attacking the two-spotted spider mite, Tetranychus urticae Koch, and the carmine spider mite, T. telarius (L.), at several locations in Alabama. The following structures of the fungus were observed: hyphal bodies which are the vegetative phase that proliferates in the hemocoel of the mite; conidia which are forcibly ejected from the body of the dead mite; secondary spores which are formed by germination of the conidia; tertiary spores; quaternary spores. The secondary spores appear to be the infective units of the fungus. Parasitism of spider mites by the fungus in the field varied with the location and collection date and ranged from an average of 30.9% in collections from Lee County (Loachapoka) to 86.4% in those from Cullman County (Cullman). Up to 88% of the live mites collected from fields where epizootics of the fungus were observed succumbed to mycosis within 2 days after collection. It appears that this fungus may play a role in the regulation of populations of some species of spider mites on cotton.