VIEW ARTICLE

Ecology and Epidemiology

Recovery of Athelia bombacina from Apple Leaf Litter. C. S. Young, Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706, Present address: Biological Laboratory, University of Kent, Canterbury, Kent, CT2 7NJ, England; J. H. Andrews, Department of Plant Pathology, University of Wisconsin-Madison, Madison 53706. Phytopathology 80:530-535. Accepted for publication 6 December 1989. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-530.

A semiselective medium (PAB: potato agar amended with 50 ?g a.i./ml of benomyl, 100 ?g/ml of chlortetracycline HCl, and 200 ?g/ml of streptomycin sulfate) was developed for detection in apple leaf litter of Athelia bombacina, an antagonist to Venturia inaequalis. The efficiency of PAB depended on inoculum level and varied between 14% (close to the detection threshold of 0.14 ? 10³ cfu/ml) and 81%, when expressed as recovery from inoculated, nonsterile apple leaves as related to recovery from inoculated, initially sterile leaves. Bacteria were eliminated and filamentous fungi and yeasts were reduced by 99.6 and 82.1%, respectively, on PAB as compared with potato-dextrose agar. The one other isolate of A. bombacina available did not grow on PAB. A mixture of inoculated and uninoculated apple leaves was incubated on the ground in mesh bags from November 1986 to May 1987 and November 1987 to mid-April 1988. Leaves were sampled every 4?8 wk and leaf pieces were incubated on PAB. During 1986?1987, recovery of A. bombacina from inoculated leaf pieces averaged 85% in the last four samples. During 1987?1988, recovery from inoculated leaf pieces averaged 96% in all samples. Recovery (averaged over all samples in both experiments) from uninoculated leaves was 21% less than that from inoculated leaves. The fungus grew 15 cm (1.2% recovery at this distance) across a mat of uninoculated leaves but did not cross a 1-cm gap of turf between adjacent mesh bags. Thus, extensive coverage by initial inoculum and a high survival rate of A. bombacina are probably the most important factors leading to extensive colonization of leaf litter.

Additional keywords: apple scab, biological control.