Biological Control of Apple Fruit Diseases by Chaetomium globosum Formulations Containing Cellulose

The disease control ability of Chaetomium globosum with and without an acid-hydrolyzed cellulose amendment was determined in field and greenhouse experiments. A formulation composed of colloidal cellulose and a vegetable oil-based spreader-sticker (Soy-Dex) that exhibited long-term foliar tenacity was utilized. The cellulose formulation was applied to apple trees alone and with C. globosum. Scanning electron microscopy in conjunction with dilution plating of leaf washes revealed that survival and growth of C. globosum were greatly enhanced by 0.5% (w/v) cellulose amendments applied to apple trees. The cellulose suspension plus C. globosum ascospores (10(5) ascospores/ml) reduced flyspeck (caused by Zygophiala jamaicensis) disease severity by 63% over the untreated control and sooty blotch (caused by Gloeodes pomigena) severity by 79% over the untreated control and 53% over the Soy-Dex control. The cellulose suspension plus C. globosum ascospores suppressed flyspeck and sooty blotch as effectively as the fungicide control. This system provides a method for supplying nutrients to foliar-applied fungal antagonists that selectively enhance the antagonists' survival and growth, thereby achieving biological disease control. (c) 1992 Academic Press, Inc.