Biological control of gray mold with Ulocladium atrum in annual strawberry crops

The efficacy of the fungal antagonist Ulocladium atrum to control gray mold in annual strawberry crops using waiting-bed transplants under field conditions was investigated. Seven field experiments were conducted with strawberry cv. Elsanta during the summer seasons of 1996-99 in the Netherlands. Treatments included untreated controls, fungicide programs, U. atrum spray programs, and crop sanitation. Under low disease pressure, U. atrum spray programs effectively reduced gray mold at harvest in four of seven experiments. Sprays of U. atrum starting at transplanting resulted in better control of gray mold than sprays starting at the beginning of flowering in only one of five experiments, Removal of necrotic leaves did not affect the level of gray mold, which demonstrated that strawberry leaves were not a significant inoculum source for Botrytis cinerea in this annual cropping system. These results suggest that U. atrum can be effective in reducing gray mold in strawberry crops, and further studies on the use of the antagonist in annual systems should consider flowering time as the best period to apply this antagonist.