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Wednesday, July 1, 2015

Rings on Peach Fruit May Be Disease, Frost

Q. What is wrong with my peaches? I left you a voicemail. I'm not much of an e mailer. These peaches are 30 miles south of Mesquite. Around 4500 elevation. The spots showed up essentially as the peaches formed. 

A. And I am not much of a phone person. I am working outside of the country right and I did get your voicemail but responding to you is easier for me through email. It allows me to collect my thoughts and gives you a written record of my thoughts and recommendations.

This is not something I have seen before on peach fruit. I have seen something similar to this on apricot. The things that jump out at me are your location south of Mesquite and your 4500 foot elevation. Three things came to mind when I saw the picture; virus disease, early spring frost damage or powdery mildew or similar disease developing on the fruit during cool, wet weather.

You didn’t tell me if you’ve seen it in previous years but if this were a virus disease you would've seen it before. The fact that you did not mention that it leads me to believe this may be a one-shot problem and not one that is reoccurring. This kind of eliminates virus diseases. But your pictures very closely resemble a virus problem.

 Peach Virus Diseases Click Here!

Although it really does not resemble late frost damage too much, because of your elevation, I am thinking it might be a possibility. All it would take is some temperatures slightly below freezing for an hour or even less just as the fruit were forming. Frost damage might cause some fruit drop while damaging others and not affecting others that remain on the tree.

 Frost Damage to Peach when it reaches near maturity

There is a microclimate in the tree fruit canopy that can affect frost damage severity for the entire tree. If this were freeze damage to immature fruit I would suspect it would be more of a problem on the north side of the tree, fruit exposed to windy locations or at the top of the tree rather than lower and inside the canopy.

Diseases like powdery mildew can leave this kind of a mark on immature fruit. It would have occurred during or slightly after rainy or wet weather and on fruit that were protected from wind by leaves or inside the canopy of the tree. Fruit in areas exposed to full sunlight and lots of air movement would, most likely, have fewer problems.
Perhaps powdery mildew on apricot

If this were a virus disease, it could have been brought in with the tree when it was purchased. It is also possible that the tree was infected by neighboring trees with the same virus. The third possibility, if the tree was grown from a pit or seed, the seed could have come from an infected tree. Virus diseases of fruit trees are usually a problem when people do not purchase “clean” nursery stock. Make sure you purchase fruit trees from nurseries that are using and producing plant materials that are certified free from diseases.

Perhaps powdery mildew on apricot
If you grow your own fruit trees from pits or seeds, disease problems like this are always a possibility. It may be rare, but it does happen. If you planted from seed and you think this may be a virus disease, there is not much you can do except live with it or replace the tree.

If you decide to live with it, it is possible the disease could spread to other plant materials in the Orchard or your neighbors.

If you think this may have been a disease problem such as powdery mildew or close relative, make sure your peach trees are not growing close to apple trees which may contribute to the problem.

If you think this is a disease problem that is not a virus, you should prune open the canopy more so that there is better air circulation and light penetration inside the canopy. Secondly, spray with sulfur applications shortly after rainy or very wet weather to help prevent the disease from developing on fruit.

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