Interaction of<i>Fusarium oxysporum</i>f. sp.<i>medicaginis</i>with Feeding Activity of Clover Root Curculio Larvae in Alfalfa

Abstract

Twenty genera of fungi were isolated over a 3-yr period from feeding sites of the clover root curculio (CRC) in roots of field-grown alfalfa. Fusarium oxysporum f. sp., medicaginis was the predominant pathogenic fungus isolated, constituting 63% of all isolates at one sampling. Root diameter, root type, and depth of feeding were not related to the isolation frequencies of specific fungi. In pathogenicity tests, 89% of all F. oxysporum isolates tested caused wilt symptoms in alfalfa. Radial internal spread of fungi from feeding sites was usually limited to the 2 mm of tissue immediately centripetal to the feeding site. F. o. medicaginis, other Fusarium spp., and other fungi were isolated from excised head capsules of field-collected, late-instar larvae of CRC