VIEW ARTICLE

Etiology

Greasy Blotch of Carnation and Flyspeck of Apple: Diseases Caused by Zygophiala jamaicensis. Kenneth F. Baker, Department of Plant Pathology, University of California, Berkeley 94720; Lily H. Davis(2), Richard D. Durbin(3), and William C. Snyder(4). (2)Mycological Supplies, 2601 Westwood Blvd., Los Angeles, California 90064; (3)Department of Plant Pathology, University of Wisconsin, Madison 53706; (4)Department of Plant Pathology, University of California, Berkeley 94720. Phytopathology 67:580-588. Accepted for publication 16 August 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-580.

Greasy blotch of carnation and flyspeck of apple are caused by the fungus, Zygophiala jamaicensis (perfect state, Schizothyrium pomi). Inoculations with single-conidia and single-ascospore isolates produced both stages on apple fruit. The pathogen occurs on at least 78 species in 36 families of flowering plants over much of the temperate and tropical world. The fungus usually removes the waxy bloom from the cuticle and forms characteristic clusters of pseudothecia (“flyspecks”) in the colony. It can utilize carnation wax or paraffin as a carbon source in vitro. Utilization of the wax on carnation foliage by the mycelium produces a greasy appearance that also may develop on the upper stem, reducing flower marketability. Conidia are forcibly discharged and airborne. Since pseudothecia rarely or perhaps never mature on carnation, conidia are important in spread in glasshouses, where there is no need of the pseudothecial stage. Mature pseudothecia develop on apple and other plants outdoors, and ascospores discharged in the spring facilitate distant dissemination; conidia apparently are an intensification mechanism, important because each infection is restricted to about 2 cm in diameter. Control on glasshouse carnations is by maintaining relative humidity below 85%. In leaky, poorly ventilated glasshouses fungicidal sprays may be necessary. Destruction of carryover inoculum, plus fungicidal sprays, will control flyspeck on apple.