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Ceratocystis fagacearum and C. piceae on the Surfaces of Free-Flying and Fungus-Mat-Inhabiting Nitidulids. Jennifer Juzwik, Graduate student, Department of Plant Pathology, University of Minnesota, St. Paul 55108; D. W. French, professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108. Phytopathology 73:1164-1168. Accepted for publication 6 December 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-1164.

Free-flying and fungus-mat-inhabiting nitidulids (Coleoptera: Nitidulidae) were collected from two oak wilt areas in Minnesota during the spring of 1981. Washings from 1,043 free-flying beetles attracted to two types of bait traps from 30 March to 26 June in the Carlos Avery Wildlife Management Area, near Wyoming, MN, were plated on agar media. Ceratocystis fagacearum was isolated from seven nitidulids: one collected 1 April and all others collected from 18 May to 19 June, 2- 3 wk after large numbers of sporulating fungus mats were detected. C. piceae was recovered from seven beetles trapped during 3 wk. C. fagacearum was recovered from 80 and C. piceae from 17 of 98 nitidulids collected on five dates from mats on northern pin oaks at Eagle Lake, near Big Lake, MN. From 30 to 760,000 viable spores of C. fagacearum were estimated to be present on the beetles. By scanning electron microscopy, conidia and ascospores of C. fagacearum were found on all external body parts of the insects. Conidia were the predominant spore type on beetles collected in April; ascospores prevailed in May. By carrying C. piceae, nitidulids may play a role in the natural biological control of C. fagacearum.

Additional keywords: epidemiology, insect-vector relations, sap beetles.