Thanks Alan for your spray dates. Maybe I’ll spray late June, late July, late Aug. Yeah I suspected university overkill on those spray recommendations, helps to hear your confirmation.
I’ll need to buy Captan if Immunox isn’t sufficient. Goldrush is forcing me out of organic mode but I only have two trees. Wonder what organic growers with many trees will do? Goldrush was an organic star.
I think I got reasonable success when I spotted it early and did a single spray- it did SEEM to delay defoliation by at least a month, which is generally adequate to assure good apples. What I did like about the 2 spray last year is that the bumper crop that received it were the most beautiful apples ever to come from the 2 orchards it was done. I was surprised at how much they reduced fly speck and sooty blotch. It was clearly much better than sites that got no fungicide through summer.
Not saying it would work on Goldrush in the same way, what a summer fungus magnate!
I believe most russets are highly susceptible to MLB as well as anything yellow related to YD.
@alan I feel my leg being pulled about russets. I don’t see any russets listed in articles about MLB.
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2021 European research identifies certain Malus species (e.g. Malus baccata) with strong resistance to MLB that apparently has been renamed Diplocarpon coronariae.
Interesting, but not very hopeful at this point. I will be sticking with my 2 extra summer fungicide sprays.
Agree. Trying to find an organic spray that will work on this but don’t think they have the residual effect of say Immunox so would require a lot more sprays. Harder and harder to grow no-spray or organic apples on east coast. This new disease so far spares pears, right?
No problem on pears- we already have psyla and other fungus diseases to complicate protection. At least Surround works great against psyla.
GoldRush and Ashmead’s Kernal were to two of my mall collection most affected by what I am guess in was MLB. Another small data point in favor of the russets hypothesis?
None of my trees suffered from it besides the russet Hudson’s Golden Gem- I gave it no summer fungicide when the disease first showed up in my orchard because it doesn’t get sooty blotch or flyspeck. I grow pretty apples to help me sell fruit trees. Golden Russet is also quite susceptible.
I haven’t had any problems with MLB so far but who knows what the future may bring. Maybe a list could be assembled listing cultivars and their resistance to MLB? Something similar to the Summer Rot thread since it doesn’t appear there are any real sources that document resistance or susceptibility to MLB.
Summer Rot thread-
Here’s the start of a list, source Organic Control of a New Apple Disease: Marssonina Leaf Blotch - SARE Grant Management System
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Just to try something I began spraying the apples and peaches with bacillis subtilis (Serende) in September. I was hoping to see if this has any effect on the appearance Marssonina. I left the top of a Golden Russet unsprayed as a control of sorts. To date I have seen no signs of Marssonina anywhere, perhaps since it has been rather dry this summer. Has anyone seen any yet this year?
I’m seeing in in shaded parts of trees, but not at a damaging level so this is a bad year to determine efficacy of materials here in S. New York. I tend to wait until I see some research before spending money on a pesticide to control a pest but Mars hasn’t been well researched in this country and I am curious about your small experiment- it’s too bad the manufacturer doesn’t do an extensive evaluation, starting by deliberately inoculating leaves that have been sprayed with Serenade, perhaps in a greenhouse. It wouldn’t seem to be very complicated to research this.
It will be difficult to determine efficacy on such a small scale, but I hope other growers on this forum try your experiments. On a wetter year we may accumulate some evidence. I guess I could try it in my nursery.
My lists so far: Clean so far and unsprayed: Belle de Boskoop; Enterprise; Sundance. .
Susceptible: Goldrush; Monark; Sweet Sixteen.
Update: the more I look, especially at interior leaves, the more I’m seeing it, so any “clean” description won’t mean much for another month and possibly for another year or two of observation.
Tomkin’s King, Mutsu, Hudson’s Golden Gem, Yellow Delicious and Baldwin are all susceptible.
I believe I have this Marssoninia here again this year ( second year) defoliation starting in August, by early September lower part of Trees look bare of leafs. If this is the new normal ? I have little hope for my unsprayed apple orchard.
The state took leaf samples last year, did not find marssonina .
That does not mean it’s not here. I believe it is ……
Looks really bad !
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
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.