Second-level Integrated Pest 

 Management, 1991 to 1993: Diseases 



Daniel R. Cooley and Ryan Elliott 



Department of Plant Pathology, University of Massachusetts 



Jennifer Mason and Starker Wright 



Department of Entomology, University of Massachusetts 



Wesley R. Autio 



Department of Plant & Soil Sciences, University of Massachusetts 



Over the past three seasons, we have been at- 

 tempting to develop disease-management strategies 

 for apple which will both optimize fungicide use 

 against diseases and integrate pest management 

 across disciplines. The approach relies heavily on 

 monitoring pathogen development for two key apple 

 diseases, using cultural approaches to manage these 

 diseases, and using fungicides which will have the 

 least non-target efiFects. It is obvious that manage- 

 ment of diseases in apples without fungicides is not 

 possible, but we feel that it is possible to improve the 

 efficiency of summer fungicide use by developing a 

 better understanding of and appropriate monitoring 

 techniques for summer disease pathogens, particu- 



larly the flyspeck fungus, and such efficiencies, 

 combined with second-level arthropod management 

 methods (e.g., Christie et al., 1992) may reduce the 

 impact that pesticides have on mites and other non- 

 target arthropods (Wisniewska et al., 1993). This 

 article summarizes the results of the program in 

 commercial blocks consisting of scab-susceptible 

 cultivars. Other aspects of the research, dealing 

 with summer pruning for disease management, fly- 

 speck epidemiology, and the effects of the second- 

 level IPM approach in blocks of scab-resistant 

 apples, are reported separately. 



Early Season Management 



For purposes of disease management, 

 the apple production season can be divided 

 into two parts. These parts coincide closely 

 with the two parts of the season used in 

 second-level arthropod management. For 

 diseases, early season management focuses 

 on apple scab. We have used a delayed sterol 

 inhibitor program (Cooley and Spitko, 1992) 

 enhanced by measurement of potential as- 

 cospore dose (PAD). For the purposes of 

 second-level IPM, we have used a threshold 

 of 500 ascospores per square meter (Dr. 

 William McHardy, pers. comm.). PAD data 

 were not available for 199 1, because funding 

 was not available in the fall of 1990 when 

 such assessments would have been done. 



Summer Management 



After primary scab season, which usu- 

 ally ends by mid-June, the main diseases 

 concern in apples are the summer diseases, 

 typically sooty blotch and flyspeck. At the 



Fruit Notes, Winter, 1994 



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