New apple disease in NE affecting M9 trees

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It’s good that I don’t have more than 1-2 trees on M9. But, it sounds like RAD (“Rapid Apple Decline”) can hit trees on other rootstocks as well, especially anything that is stressed. So my M27’s and G65’s are automatically suspect, as mini-dwarf are stressed very easily.

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To me this sounds like the old “peach yellows” which they thought was a disease for many years but turned out to be a combination of environmental stressors (the article more or less comes to that conclusion).

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For home growers, keeping young trees vigorous would appear to be the best potential preventive. Don’t let them over set and don’t make them compete with turf or weeds. Prune for vigor when needed, removing surplus spurs and leaving plenty of annual shoots of moderate vigor. Prune back growth to such shoots.

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Is not peach yellows caused by phytoplasma? At least, that’s what I read.

I had thought that the old peach yellows from the 19th century was determined to be environmental. The phytoplasma sounds like it is different but the same name is being used. I had the old peach yellows in my orchard, the leaves get yellowish and curl in a bit and growth is slow. All my trees grew out of it. The phytoplasma trees don’t grow out of and it affects the fruit as well.

To me it sounds like what is now called peach tree short life. That’s a combination of environmental stresses and various pathogens. PTSL also has a rootstock component.

Out west they have replant disease issues with apples and other fruits. Replant issues are a buildup of pathogens in the soil that can greatly reduce tree vigor and yield. Rootstock is one component of overcoming replant disease.

Did they say if the new issues in NE are correlated at all to a replant situation? The roots may look good but I’d suspect something in the soil, ie pathogens of some sort are contributing to the issue.

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Interesting article on another unexplained apple tree disease. This time it’s M9 trees rather than Geneva trees that die for no good reason.

So far I don’t have Apple trees dying for no reason, but I do loose Peach trees to what the experts call “PTSL”. Its common in my state, especially on sandy soil.

I loose about 5% of my peach trees each year. A researcher at a peach grower’s meeting told me that PTSL had been studied for over 30 years but the exact cause was unknown.

Hope the discovery of the cause and prevention for RAD in apple trees is faster!

Blueberry: hope you don’t mind if I ask what rootstock you have your peaches on? Do you use the new Guardian rootstock a lot of places recommend, or something else?

Mostly Guardian

Interesting that in the article there is no mention of using stronger rootstocks. It may be hard to admit when so much money is invested in high density plantings, but the truth is that dwarf rootstocks are weak. Apples are tough trees by nature, we have bred them to be weak domesticated poodles. I think its time to return to the wolf, and start growing apples that are tough again. The higher costs of pruning, spraying, and lower initial yields are overcome by having trees with long lifespans and an inherent resiliency. That’s my two cents.

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The name itself (the yellows) invited confusion. Here is an old write-up from 1894 you may have already read at some point. In it, the author goes to great lengths to try to offer distinguishing symptoms of the “true” peach yellows. It’s interesting, one farmer refused to cut down his peach trees, when the authorities demanded he do so (because peach yellows was a quarantine disease) and was convicted of a misdemeanor and his trees were cut down anyway. The author claimed the farmer farmer’s trees probably didn’t even have the true yellows.

Now the true phytoplasma yellows is pretty rare in the U.S. It’s also pretty easy to identify because of the witch broom growth.

http://www.virginiafruit.ento.vt.edu/peachyellows.html

Standard trees aren’t going to come back for most commercial growers. They can’t compete with apples from unaffected areas. Growers in affected areas are more likely to go out of business. And I don’t think dwarf rootstocks are weak. I’ve had nothing but good luck with M9 and 26. And that’s in pretty severe climates in west Texas.

If you plant standard trees back where the dwarfs are dying who’s to say they won’t fold up about the time they come into full production. Peaches have had the same type issue, PTSL, on standard roots for decades.

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I understand what you’re saying, but I think chestnut raises an interesting point in general.

My understanding is that dwarfing rootstock works by restricting the flow of nutrients to the scion. So isn’t nutrient restriction a stressor? And the more nutrient restriction (i.e. the more dwarfing) the more stress you are applying?

So could it be true to say standards are, by the very fact they’re standards, stronger trees (i.e. more vigorous and less stressed?) than more dwarfing trees of the same variety? And if they’re more vigorous and less stressed, they should (theoretically) be able to tolerate diseases much better than the same tree in a dwarfing rootstock?

So dwarfing rootstocks might not be “weak” per se, but if your main goal is to have a tree live a long life and shrug off disease, then standards are the way to go.

I think your point of standards not being bulletproof (PTSL) is well-taken. But I think, at least as far as the theory goes, is not if standards are affected by PTSL, but whether we’d expect peaches on dwarfing rootstocks to show a similar, better, or worse mortality rate. I strongly suspect the dwarfing rootstock peaches would fare worse.

At any rate, I defer to your point about standards being non-viable for commercial production, but I think chestnut’s point still remains and is a good one to keep in mind.

Additionally, there ARE methods to keep standards manageable sizes. I’ve seen them in some older literature. For example, growing in a tripod. I dunno. I’m not an expert, don’t claim to be, and it might seem as if I’m challenging you, which I hope it doesn’t come across that way. I think everything you said can be absolutely true, without invalidating chestnut’s main point.

I’d welcome your thoughts or anyone else’s.

FN, I agree with VSOP, and, as I recall, Jim Cummins does also- I believe he once defined dwarfs as weak growing trees- but it’s really just a matter of semantics and what you mean by weak. However, in the elements of mother natures unpredictability, more vigorous rootsocks are the survivors over the dwarfs so I will call dwarfs relatively weak. I agree with you that more vigorous rootstocks are not going to work for commercial growers in the east- they can barely compete with west coast growers as it is. It is very expensive to keep vigorous apple trees properly pruned. They not only require more of it but they also require a lot more expertise than dwarfs. I think that’s a greater increase in expense than all the other factors combined.

I’d agree with that and generally agree with @VSOP. But there is another factor. Modern orchards are not designed for a long life like old standard trees. 20 yrs is an old dwarf orchard. By then there are new varieties and probably new rootstocks and new production systems. High density orchards are designed for a rapid breakeven, high annual profits, low labor cost, and relatively short life.

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yup

That is a good description of apples on B9 in my area. The trees just don’t grow well on most varieties.

The big advantage of all dwarfing rootstocks is their ability to get into production quickly. Even if the size of standard size trees could be managed, they take too long to produce a full crop.

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Yes, exactly. I know some crops like sweet cherries which are as big or bigger than apple trees, produce more per acre on dwarfing stock. Not sure about apples? Another factor to consider.

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As far as competition goes, standards will outperform dwarfs in the long run. Orchards on dwarfing rootstocks have a life span of 20-30 years, while seedlings can go on for a century. It really depends on the goals of the orchardist. Cider orchards don’t need pristine looking fruit. I harvest apples and pears for cideries by shaking fruit from giant trees onto tarps. I’ve collected over 1,000 pounds from individual trees that were never pruned or sprayed. The dwarf systems might be productive initially, but in the long run I see them as an expense and another example of our society’s obsession with immediate rewards. Again, its just my opinion. I have no problem if people want to plant dwarfs, I just think its not the best long term project.

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