Evaluation of Scab on Fruit of New 

 Apple Cultivars 



Daniel R, Cooley, Arthur Tuttle, James Hall 



Department of Microbiology, University of Massachusetts 



Duane Greene 



Department of Plant and Soil Sciences 



While scab resistance has not proven to be the 

 most important characteristic of new apple culti- 

 vars, it is still useful to know how susceptible new 

 cultivars are to scab. A grower is probably wisest 

 to choose a new cultivar based on marketability 

 and production, but then treat it for scab ac- 

 cording to susceptibility to the disease. 



It was difficult to control scab in 1998, and 

 a test block of new cultivars at the Horticul- 

 tural Research Center in Belchertown, MA 

 developed significant foliar and fruit scab over 

 the growing season even though fungicides 

 were applied. These cultivars were planted in 

 five replicated blocks, and we decided to evalu- 

 ate scab incidence to determine if there were 

 differences. All the trees were on M.9 root- 

 stock, except two that also were on Mark 

 (Golden Delicious and Yataka). On Septem- 

 ber 3, 1998, scab on the fruit was evaluated, 

 and incidence was calculated as a percent of 

 total fruit per tree. 



The only cultivar in the planting that is al- 

 ready widely planted commercially in Massa- 

 chusetts is Golden Delicious. Golden Delicious 

 is generally reported as not very susceptible to 

 scab, and this evaluation supported that as- 

 sumption. While Golden Delicious had about 

 10% scab incidence, scab incidence over the 

 whole planting ranged from to 49%. Gala 

 Supreme was quite resistant to scab, with 0% 

 incidence. Similarly, Sansa, a Gala x Akane 

 cross, also had 0% scab. As might be expected, 

 two scab-resistant cultivars from the Purdue/ 

 Rutgers/Illinois program, Enterprise and 

 Goldrush, and one from the New York pro- 

 gram, NY-75414-1, also did not show any 



scab. Suncrisp, progeny of a Golden Delicious 

 cross, had very little scab (6%). 



Unfortunately, two cultivars that would have 

 been very interesting to evaluate, Honeycrisp and 

 Ginger Gold, did not produce fruit in 1998. 



Table 1. Evaluation of fruit scab in a variety 

 block (NE 183) at the Horticulture Research 

 Center, Belchertown, MA, September 3, 1998. 



Means followed by the same letter are not 

 significantly different at odds of 19:1. 



12 



Fruit Notes. Volume 63 (Number 4), Fall, 1998 



