Disease Note.

Anthropod Carriers of Cytospora Propagules in Stone-Fruit Orchards. A. W. Helton, Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow 83843. J. B. Johnson, and R. D. Dilbeck. Department of Plant, Soil and Entomological Sciences, University of Idaho, Moscow 83843. Plant Dis. 72:734. Accepted for publication 30 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0734C.

Because ladybird beetles were observed congregating at gumming Cyrospora cankers, 701 arthropods were collected between bloom and fall frost and tested for contamination with Cytospora cincta Fr. Contaminated individuals included 23 ladybird beetles (Hippodamia convergens Guerin-Meneville; Coccinella novemnotata Herbst.; 13.8% of 167), 10 hunting spiders (Microphantidae; Lycosidae; Salticidae; 12.8% of 78), 4 lygus bugs (Lygus spp.; 11.1% of 36), 3 honeybees (Apis mellifera L.; 8.8% of 34), 3 March flies (Bibio sp.; 12.0% of 25), 3 stinkbugs (Brochymena sp. and Chlorochroa sp.; 25.0% of 12), and 16 miscellaneous insect species. Transmisions were attempted with 15 artificially contaminated ladybugs using cages amd scrape wounds. After 251 days, 100% of the wounds walked over by contaminated beetles had developed Cytospora cankers (av. 11.4 cm²); uncontaminated beetles produced no infections. These data suggest that orchard arthropods play an important role in distribution of Cytospora fungi. Since ladybugs exploit alternate food sources, including gummoses, when aphid populations are low, chemical control of aphids in orchards infested with Cytospora may lead to increased incidence of disease.