Disease-management components of advanced integrated pest management in apple orchards

Reducing fungicide use in commercial apple orchards is particularly problematic, although success would positively effect other aspects of orchard ecology, primarily arthropod management, and may alleviate ecological and food-safety concerns. Methods for reducing fungicides were tested in the context of advanced integrated pest management (IPM), in which arthropod pests are managed with minimal use of pesticides following the petal-fall stage of apple growth. The potential ascospore dose (PAD) method for predicting inoculum density of Venturia inaequalis, which causes apple scab, was used in conjunction with ascospore-maturity evaluation and ergosterol-biosynthesis-inhibiting fungicides to manage scab in advanced IPM blocks. In 78% of the cases studied, PAD indicated growers should delay the first fungicide application, but growers actually followed this recommendation in only half of these cases. Where growers followed the recommendation, they applied significantly less fungicide, saving an average of over one application during the primary apple scab season, a 26% reduction, A combination of summer pruning and limited captan use was recommended for management of flyspeck (caused by Schizothyrium pomi) and sooty blotch (caused by three associated fungi). Growers generally followed the advanced IPM recommendations, and during the summer applied 34% less fungicide in the advanced IPM blocks. The program showed that growers could achieve significant fungicide reductions in apples using these methods, although it also indicated that they were sometimes reticent to implement them. (C) 1997 Elsevier Science B.V.