New apple disease in the Northeast-Marssonina Leaf Blotch

Did the state give you a diagnosis? It’s new so maybe not on their radar yet.

They found frog eye leaf spot .Which has been here for years and never caused such problems. Also they did not believe that Marssoninia was here but they never heard of it either

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I just planted a Goldrush this year. Knowing that makes me say Uggg.

MLB has been a known disease in the U.S. long before it appeared on apples. I used to get early defoliation on my apple trees in very wet years but never bothered to send in a sample, I just blamed it on the weather. When we got drier weather the problem disappeared.

MLB on apples was discovered by Cornell because people started sending in samples, but not from commercial orchards, where it isn’t a problem yet, that is conventional commercial orchards that keep synthetic fungicide on leaves until harvest (at least- sometimes they treat the harvested apples as well, for greater shelf life).

Has the fungus evolved to be able to attack apple leaves or have the 3 consecutive very wet seasons been the cause of susceptibility? This year we had a very wet spring but drought during summer and the disease is only showing up deep in the canopy of trees pretty late, not something anyone would likely have tested for- it looks like MLB to me, but I would not have noted the problem before it became a big problem in preceding years.

A tree can lose its leaves late and still be productive of excellent apples. We still don’t know if MLB will be a persistent problem and if it becomes one, hopefully we will become better informed about treatments.

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