Interaction of Fusarium oxysporum f. sp. medicaginis with Feeding Activity of Clover Root Curculio Larvae in Alfalfa. K. T. Leath, USDA-ARS, U.S. Regional Pasture Research Laboratory, University Park, PA 16802. A. A. Hower, Department of Entomology, Pennsylvania State University, University Park 16802. Plant Dis. 77:799-802. Accepted for publication 22 March 1993. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1993. DOI: 10.1094/PD-77-0799.

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. The addition of 50 CRC eggs to a growth medium infested with F. o. medicaginis inoculum significantly increased the severity of Fusarium wilt in greenhouse experiments.

Keyword(s): Sitona hispidulus.