What you are describing with the lesion -- the raised black dots = sounds exactly what we see with Marssonina infection. Depending on when you sprayed captan and how much rain you received afterward (i.e. washing off the captan), this could have been the entry point for Marssonina. I noticed Marssonina on my trees that I sprayed conventionally all season; however, we stopped spraying captan at the beginning of September...and we had close to 15 inches of rain fall during the month. And we never reapplied...consequently, Marssonina showed up. Although captan keeps the disease in check, you need to keep in mind it will wash off with 1-2 inches of rain and needs to be reapplied.
Kari Penn State ________________________________ From: apple-crop-boun...@virtualorchard.com <apple-crop-boun...@virtualorchard.com> on behalf of David Kollas <kollasorchar...@gmail.com> Sent: Tuesday, October 9, 2018 7:52:30 PM To: Apple-crop discussion list Subject: Re: [apple-crop-2] Apple leaf disorder Dan, Brian, Kari, Mo, and others: Having read your comments and links, I looked more closely at my symptoms. I was wrong about its association with yellow delicious breeding. I can find it in Macoun, Empire, and many others. The symptom common to all that I looked at with magnifying glass was scattered dark blackish raised dots in the live or dead “spot” that often retains its green color after surrounding areas have yellowed. I did not find any affected leaves that exhibited the concentric bands noted in the 2012 blog, with click-enlarging photograph, by Dave Rosenberger on Glomerella leaf spot. Therefore I conclude it is not Glomerella infection. If it is Marssonina leaf spot, I would not expect it to have survived all the captan sprays I have administered. Sooty Blotch and Flyspeck, in spite of all the favorable conditions for those diseases, are rare here at this time. I suppose it could have a physiological cause that made areas of the leaves susceptible to opportunist fungi, and some petri dish work in a lab might isolate and identify those raised black dots. It is discouraging to loose the leaves before harvest, not knowing why, nor what could have been done to avoid it, David Kollas > _______________________________________________ apple-crop mailing list firstname.lastname@example.org https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fvirtualorchard.net%2Fmailman%2Flistinfo%2Fapple-crop&data=02%7C01%7Ckap22%40psu.edu%7C649d76dfa11e4718859f08d62e424d3e%7C7cf48d453ddb4389a9c1c115526eb52e%7C0%7C0%7C636747259636191839&sdata=ybEHt%2Fu8TcDOIW8KnB%2FWh0J9W3%2FV%2BPkhd8%2BTyHsr7cs%3D&reserved=0
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