Help! Dark spots on peaches (w/ pictures)

digdugdiggy(8.5)May 26, 2010

My Peaches have developed some sort of dark spotty fungus or bacteria. What can I do to help with this? Are these fruits gone? I heard about 1% bleach water, but I am would prefer something more organic. Any suggestions?

Also, how can I tell when the Peaches are ready? A few seem very red but not yet soft. Do they stay hard on the tree? What time of year are peaches usually harvested? Thanks!

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Scott F Smith(6B/7A MD)

That looks like peach scab. There are several treatments; I use a sulphur spray at 6-8 weeks after bloom, which was not long ago for me. The fruit is still perfectly edible, but some fruits that get it badly do not size up as well and may have tough skin.


    Bookmark   May 26, 2010 at 10:40PM
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Can I spray the sulfur solution on the fruits? Or is it too late. I need prevention prior?

    Bookmark   May 27, 2010 at 12:47AM
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I believe your peaches have peach bacterial spot, although if you Google this term and "peach scab", you will find the two diseases difficult to distinguish. After years of wrestling with this distinction, I more or less concluded that bacterial spots are usually spread farther apart, as yours are, often beginning on the lower part of the peach, and are darker in color. I believe that peach scab usually begins at the top of the peach near the stem, then spreads outward, eventually forming a solid mass.

I have had both of these diseases many times, and both are highly damaging to peaches. Yes, you can still eat them, but it's not much fun to do so, since you cannot even properly peel a peach with either of these diseases, which often affect the flesh to a depth of 1/4 inch or more. Many people peel peaches before eating, and peeling is standard procedure before freezing peaches, which is what happens to most of ours. While it is very important to try to prevent even minor damage to the fruits, in many cases the scab or spot spreads and stops growth of the peaches which of course is even worse.

I wish you would not require us to guess where you live, but from the size of those peaches I have to guess somewhere in the coastal or interior Southeast. The rainy spring weather and early warming of the entire mid-Atlantic favors both of these diseases. Once these diseases are established on peaches, there is nothing to be done, since prevention is the key here, not cure. Application of bleach would be very unwise, and sulfur would not help at this point either. In fact, I believe sulfur to be useless against these diseases at any stage.

Bacterial spot can also infect the leaves of peach trees, causing them to spot, turn yellow, and eventually fall off. The disease is also expressed by lesions on the limbs and twigs that exhibit sap leakage. Three or four years of unchecked bacterial disease can easily kill a peach tree. I have had pretty good luck with control of bacterial disease by applying two dormant sprays of a strong copper product called Kocide. Applications should be made in late fall, and again just before bud break.

The most effective preventative that I have found against peach scab, which you will also no doubt see sooner or later, is a good spray of Daconil fungicide immediately after shuck split, and another around a week later while the peaches are still very small. I have tried other fungicides, including Captan and Topsin, and they do not seem to work for me. No spray will be effective once the peaches begin to size up, because the diseases are already there, though you cannot yet see them.

You don't mention the variety of peach you have there, but most modern peach varieties are bred to color up red well before they are soft ripe, and can hang on the trees for over two weeks while bright red and still not be soft and sweet enough to pick. Commercial growers have discovered that consumers prefer bright red peaches, but still need a hard peach to ship. Truth be told, many yellow peach varieties taste much better than the highly colored reds. Color is not a good indicator of flavor.

Finally, if keeping the "organic" faith is more important to you than growing good peaches, I doubt that you will ever grow decent peaches. There are some places in the country, mostly those that see warm dry weather during the growing season, that could pull off an organic peach, but not many of them are east of the Mississippi river. And so far we have talked only about diseases, not insects like the plum curculio and oriental fruit moth, which are normally present in the same areas that suffer from disease. Nor have we discussed brown rot, which often strikes later in the season. For the backyard orchardist, growing peaches is quite difficult, requiring all the help available from timely use of fungicides and insecticides.

Don Yellman, Great Falls, VA

    Bookmark   May 27, 2010 at 2:33AM
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Scott F Smith(6B/7A MD)

I agree peach scab and bacterial spot are hard to tell apart; in fact for several years I thought my peach scab was bacterial spot. Here are some reasons why I think this is peach scab. First, bacterial spot usually produces more irregular spots, not so round or so even in size and shape. Second, every time I have seen bacterial spot on the peach fruits it is also on the leaves, and your leaves look perfectly clean. Peach scab only affects the fruit.

I agree with Don that peaches are hard to grow in a warm humid climate if thats where you are. They are even harder to grow organically, but not impossible because thats how I grow them. The diseases on peaches I don't find that hard to deal with organically; copper at leaf fall and just before leaves push out in the spring usually does in bacterial spot, and sulphur at 6-8 weeks from bloom is highly effective on peach scab. The biggest problem are the bugs, the plum curculio and oriental fruit moth, which are much more easily treated using synthetic chemicals. I am surprised you don't have any signs of those on your fruits, maybe its a young tree and they have not shown up yet. Or maybe you are in California.


    Bookmark   May 27, 2010 at 8:35AM
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Thank you all for the great replies!
I live in Houston, Texas.

The peach trees dont seem to have many problems here, other than this bacteria. Sometimes, when they are dormant (just sticks) we get a strange problem where they spew out sap from the trunk into little bubbles of amber. We think this is because of some beetle, but havent caught any in the act.

We have two trees: One has peaches a little larger than a golfball, slightly smaller than a baseball. The other has golfball sized fruits. The peaches on top are turning bright red, but are still very firm.

Does a copper sulfate solution work when applied in the fall? (To clarify, only spray when they are dormant trees?)

    Bookmark   May 27, 2010 at 2:40PM
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olpea(zone 6 KS)


Fall copper is mainly for peach leaf curl and won't have much (if any) effect on your fruit issue.

Two possibilities have been mentioned for your malady. While Don gave much good advice, I'll have side with Scott on this one and go with peach scab. Every time I've seen bac. spot on my peaches, I see quite a bit of evidence (shot hole) on the leaves. In fact, I always see it on the leaves first. Your leaves look pretty clean.

Copper won't do anything for scab. For an organic approach, try the sulphur. I have no experience with it's efficacy against peach scab since I use synthetics. However, you may not be able to get by with one spray as Scott does. Peach scab has the potential to affect the fruit all season long. One of your photos shows a possible shoot canker. Scab can cause those cankers (as can bac. spot) which would indicate a high level of inoculum.

    Bookmark   May 27, 2010 at 3:35PM
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There is nothing strange about the sap-spewing from the trunk of your tree. That is most likely bacterial canker disease, and is closely related to the problems on your fruit. Beetles are not involved in this process. If your leaves are still asymptomatic, I cannot explain that except to say that all symptoms of bacterial disease do not necessarily appear simultaneously in a package, though eventually I believe they will.

The type of copper I use to combat this complex of diseases is not copper sulfate but copper hydroxide, which is a form that is much more effective on fruit trees. The Kocide product I use is very high in fixed copper equivalent, which is the standard usually used to judge the strength of a copper solution. Bacterial diseases overwinter on the trees, and continue to build year after year unless the process is interrupted. I suggested applying copper both in spring and fall when symptoms are present, but why would you not also apply in spring just before bud break?

Copper may also be somewhat effective against peach scab, to the extent that the disease overwinters on the trees, but this disease is capable of blowing in afresh every season, which makes the spring application of an effective fungicide important. I do not consider sulfur to be a particularly effective fungicide for a tenacious foe like peach scab, which is why I suggested Daconil, applied very early when the disease arrives.

I am surprised you do not have regular issues with plum curculio and oriental fruit moth in the Houston area. How long have you been growing peaches, and are you confident you can identify damage from these insects? When peaches begin to turn red before achieving full size, that is usually because their growth has been interrupted or stopped entirely. Such peaches will not grow up to what you want them to be. You need to take a closer look at your peaches to figure out what is really going on, and it could be more than one thing, although the bacterial spot alone is enough to pretty well ruin your peaches.

Don Yellman, Great Falls, VA

    Bookmark   May 27, 2010 at 4:04PM
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Okay, I think I understand.
My peaches are suffering from:
1. Peach Scab (The spots on the fruits)

2. Canker disease (The mauled looking bark)

After some research, it seems that the only cures are preventative. I will work harder next year to try to solve my problems. Apply copper hydroxide in fall and spring.

I looked into the Curculio and fruit moth, but I don't recognize either of those bugs, or their damage marks.

Some of our other trees have caterpillars that fold leaves over and make a little home in there. I cannot identify these, but I am smashing them just about every day.

I have had success with sulfur on apple trees: We had some apple trees that got completely covered with a powdery white fungus. 3 full surface applications of sulfur took care of that nicely, but that is a much different problem.

Are there any other major problems that I should keep an eye out for? Thanks so much for all the advice!

Would some more pictures of something help identify my problems?

Houston, TX

    Bookmark   May 27, 2010 at 4:36PM
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