Evidence for the Involvement of Soilborne Mites in Pythium Pod Rot of Peanut

Abstract

Mites of the genus Caloglyphus (Acarina:Acaridae) were associated with more than 50% of decaying peanut pods collected in a field in which pod rot was caused by P. myriotylum. Laboratory cultures of these mites could be maintained for several months on P. aphanidermatum growing on potato-dextrose agar slant tubes. In food preference tests C. micheali was attracted to P. myriotylum; up to 98% of all mites responding in food preference tests preferred P. myriotylum over 5 other fungi isolated from peanut pods. Viable colonies of P. myriotylum were obtained from 90% of the fecal pellets collected from C. micheali after feeding on mycelial mats of the fungus. P. myriotylum oospores also remained viable after passing through the alimentary canal of C. micheali. Pythium pod rot was reduced significantly in field and greenhouse tests of several acaricides and broad spectrum insecticides. In greenhouse tests the addition of soil-borne mites to field soil infested with P. myriotylum significantly increased the incidence of peanut pod rot.