14 



through mid-June, to develop weekly messages and distribute them to Regional 

 Fruit Agents, to test new ergos terol-synthesis inhibiting fungicides for 

 potential use in the program, to continue with work on disease-resistant 

 apples, and to participate in grower training sessions for sprayer calibration 

 and disease-management information. 



Leaves for the apple scab maturity assay were collected from an abandoned 

 orchard in November, 1985, placed in hardware-cloth cages, and left out in a 

 non-sprayed orchard over the winter. These cages were distributed to the 6 

 sites in March. Weekly collections were made by Kathleen Leahy, Jim Williams, 

 and Bill Coli. Leaves were then examined, squash mounts prepared, and counts of 

 mature ascospores made. 



Squash mount data indicated that primary season lagged behind tree 

 development by up to 2 weeks. This meant that early season sprays were not 

 needed. In most areas, fungicide applications could have been delayed until 

 half-inch green or tight cluster at the earliest. In fact, no fungicides 

 probably were necessary until bloom this year. Wetting periods monitored at 

 Belchertown showed that there were no Mill's infection periods before May 7, 

 because during wet periods weather was too cool for scab development. At this 

 time most trees were in early bloom. There were several heavy infection periods 

 through the rest of May. A heavy wetting period (72 hours) occurred June 5-8, 

 and the effects of this are still being discussed. Scab development on late 

 terminals during the end of June suggested that there was a primary infection 

 period at the beginning of the month, and that the maturity evaluations had 

 estimated the end of the season before it had occurred. The alternative 

 suggestion is that during mid-May, primary infections occurred, and during the 

 heavy rains in early June, secondary scab was spread. Scouting in the tops of 

 trees showed lesions on early terminals and clusters, indicating that these 

 infections had occurred in mid-May. Because of frequent rains, extreme 

 pressure continued through the summer, causing greater than normal fruit scab 

 in some orchards. 



Pest messages have stressed the need to scout orchards until infections 

 which might have occurred have had a chance to show up. During this period, 

 sprays should be applied as they were during primary season. However, some 

 growers immediately reverted to a reduced frequency and/or rate in their spray 

 schedule at the announced termination of primary season. In our tests, such a 

 reduction this year resulted in terminal scab infections of the type reported 

 around the state. This confirms our original recommendation: after the end of 

 primary season, orchards must continue to be sprayed on a primary schedule for 

 a period sufficient to allow any primary infection to be visible. 



Other infections appeared to be caused by a failure to spray before or 

 immediately after critical infection periods in May, or by a failure to cover 

 the tops of large trees. Large trees were infected much more frequently than 

 properly pruned trees on dwarfing rootstocks. Scouting the tops of trees 

 revealed primary infections better than scouting other locations. 



Tests at the HRC also looked at the efficacy of 3 ergosterol-inhibit ing 

 (EI) fungicides, Rubigan'" (Elanco) , Nustar'" (Dupont), and A-815'" (Uniroyal) 

 and compared them to a standard dithiocarbamate, Manzate™ 200. In some 

 treatments, the EI compounds were combined with the Manzate. In general, 

 sterol-inhibit ing fungicides were better than Manzate at controlling primary 



