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Disease Control and Pest Management

Identification and Distribution of Fungal Parasites of Heterodera schachtii Eggs in California. Elizabeth A. Nigh, Former graduate research assistant, Department of Nematology and Plant Pathology, University of California, Riverside 92521, Present address of senior author: Arizona Western College, Agriculture Department, P.O. Box 929, Yuma 85364; Ivan J. Thomason(2), and S. D. Van Gundy(3). (2)(3)Professors, respectively, Department of Nematology and Plant Pathology, University of California, Riverside 92521. Phytopathology 70:884-889. Accepted for publication 4 March 1980. Copyright The American Phytopathological Society. DOI: 10.1094/Phyto-70-884.

Acremonium strictum and/or Fusarium oxysporum were isolated from eggs within Heterodera schachtii young females and cysts in 20 of 25 fields infested with the nematode. Investigation of H. schachtii egg parasitization in greenhouse cultures indicated the presence of the nematode and one or both fungi in 26 of 29 soils tested. Both fungi parasitized eggs on agar and in soil when either mycelial or conidial inocula were used. The fungi also parasitized eggs of other nematodes on agar and both fungi grew saprophytically in H. schachtii eggs killed by heat. A. strictum and F. oxysporum invade the female of H. schachtii through natural openings. There was no destruction of the cuticle or disruption of subsequent development of the cyst wall. In the greenhouse, A. strictum was weakly parasitic on seven of nine plants tested, including sugar beet. The amount of parasitism exhibited by isolates of both fungi in laboratory and in greenhouse studies suggested that the fungi may be useful in the control of H. schachtii besides being important as plant pathogens in some crops.