Apple scab primary season probably ended with the May 22nd wetting period and lesions from this infection period should start appearing by June 4. Scout your orchard now and through June 4th. If you are scab free by June 4th, you will probably be all set for scab and can switch to a more relaxed summer fungicide program. For many growers the summer fungicide program will be applying captan every 2-3 weeks and adding Topsin M every other spray. Repeat spraying in 2 weeks if only captan is applied. Repeat spraying in 3 weeks if using captan plus Topsin M. Once we’ve received 2 inches of rain we consider pesticides washed off and needing to be reapplied. If you have been using EDBC fungicides (Dithane, Manzate, Polyram) at half rate, you probably have time to apply an EBDC one more time before reaching the 77 day preharvest interval.

At URI’s East Farm Orchard we haven’t sprayed yet this year and I found scab lesions on May 23. I’m sure lesions were visible before then but I hadn’t looked. Attached are two pictures of scab seen May 23nd. The first picture shows the olive-green smudge of a scab lesion near the leaf tip and the other shows a leaf heavily infested with scab. If you find scab in your orchard now the best thing to do is apply 2 full rates of captan 7 days apart.