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APPLE DISEASE MANAGEMENT IN MASSACHUSETTS: 

 1981 RESULTS AND A FOUR YEAR SUMMARY 



1 2 



Christopher M. Becker , Kristin G. Pategas , 



and William J. Manning^ 

 Department of Plant Pathology 



The Massachusetts Apple Integrated Pest Management (IPM) 

 program has been in operation for 4 years. As the IPM program 

 enters its final year, we present the disease management results 

 for 1981 and a 4-year summary of the disease management program. 



1981 Season 



During the 1981 season, 17 commercial apple orchards were 

 involved in the disease management part of the IPM program. 

 Eleven of the orchards were scouted and visited on a regular 

 basis and participated in apple disease management. Modified 

 hygrothermographs were placed in each orchard so that fungicide 

 sprays for apple scab could be applied on an after- infection or 

 "kickback" basis. The other six orchards were not in the IPM 

 program and served as controls. 



The 1981 growing season was most unusual. Usually the 

 apple tree buds and the spores of the apple scab fungus ( Venturia 

 inaequalis ) develop at about the same rate and growers begin spray- 

 ing when green tissue shows. However, in 1981, green tissue 

 developed prior to the discharge of scab spores, but it was diffi- 

 cult to convince growers not to spray and some growers applied 1-2 

 unnecessary sprays. Also, many wetting periods were encountered 

 and it was difficult in the early growing season to reduce fungi- 

 cide sprays and manage apple scab. 



The wetting periods for primary scab development at the 

 Horticultural Research Center in Belchertown, Massachusetts are 

 shown in Table 1. The ascospores did not begin to mature until 

 near the end of April, whereas green tissue was present on April 

 14. 



The first 2 significant apple scab infection periods at the 

 Horticultural Research Center (Table 1) occurred when 81 mature 

 scab spores were released during two severe infection periods at 

 tight cluster and pink. Despite the low percentage of spores, 

 the relatively long wetting periods (50 and 27 hours) were most 

 important in designating them as significant and severe infection 



1 



IPM technician 

 2 



IPM scout 

 3 



Professor of Plant Pathology 



