peach scab on the fruit - Ask Extension
Last year my peach trees had scab on the fruit. I'm pretty sure it is made worse by the automatic lawn sprinklers, which I schedule to come on about 6...
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peach scab on the fruit #927203
Asked March 31, 2026, 5:33 PM EDT
Last year my peach trees had scab on the fruit. I'm pretty sure it is made worse by the automatic lawn sprinklers, which I schedule to come on about 6 AM several times a week. If I changed the time would that help? Although I doubt we will get fruit this year due to the predicted impending hard frosts, and the trees being in full bloom right now, just in case, I would like to spray with the least toxic spray. Or perhaps if we don't get fruit this year, would the spoors die and not be a problem the 2027 year? My research on-line seems to be conflicting, to spray during bloom or right after bloom. What spray would you recommend and when do I spray?
Thanks!
Klamath County Oregon
Expert Response
https://ipm.ucanr.edu/agriculture/peach/scab/#gsc.tab=0
Hi Charlene, I have been so happy to see you registered for some of the zoom classes we have been offering! I hope you are doing well.
Regarding peach scab- If the problem is correctly diagnosed as scab, you're right, wetting the blooms is aiding the fungus. Scab is most common in areas with warm, humid springs. We had a pretty wet spring 2025, compared to other springs, as well.
The link above from UC Davis has great info and suggests two sprays. From the document:
within 3 weeks after full bloom to protect developing fruit, and again at 5 weeks if disease was severe the previous year, will reduce fruit infection. Fungicides applied during bloom for brown rot and at petal fall to control shot hole will also reduce the spread of scab if appropriate fungicides are chosen.
The UC Davis info is usually quite reliable. They also list several possible fungicides, some of which are not available to folks without a pesticide license. The one I was able to find that homeowners can buy:
The 2.5 gallon is available on Amazon, but probably way more product (and $$) than you need unless you have quite a few trees.
Here's a helpful guide for most peach/ nectarine problems:
https://extension.oregonstate.edu/catalog/ec-631-managing-diseases-insects-home-orchards#peaches-nectarines
Using the info from UC Davis above re sprays for brown rot, cross referenced with the table in the OSU guide, these fungicides might be appropriate:
captan, chlorothalonil, or propiconazole
Ive been hearing some people say they are having a hard time finding Captan, but you might already have some.
Changing the time of the sprinklers won't change much- you're watering at the best time, when the sum is about to come out and dry the leaves. is there a way to move the sprinklers so they aren't wetting the tree leaves?
You're also right that the frost may keep you from getting peaches this year- but I don't think that will make all the spores go away.
Here's some info from one of my disease diagnostic guides:
Twigs, leaves and fruit are infected, but the symptoms are most noticeable on fruit. The spores are overwintering in twigs and bark crevices. It's a good idea in future years, to do a dormant oil spray before the trees bud out in late winter. The dormant oil goes all over the branches and twigs- you want really good coverage. This product is least toxic environmentally, and smothers a wide range of fungal and bacterial residue as well as some insect eggs. It's too late for that spray this year, but it is the one preventative spray we can do in our home fruit trees that covers a lot of bases.
I hope you find this helpful! Let me know if you want clarification on anything. Best wishes, Nicole
Hi Charlene, I have been so happy to see you registered for some of the zoom classes we have been offering! I hope you are doing well.
Regarding peach scab- If the problem is correctly diagnosed as scab, you're right, wetting the blooms is aiding the fungus. Scab is most common in areas with warm, humid springs. We had a pretty wet spring 2025, compared to other springs, as well.
The link above from UC Davis has great info and suggests two sprays. From the document:
within 3 weeks after full bloom to protect developing fruit, and again at 5 weeks if disease was severe the previous year, will reduce fruit infection. Fungicides applied during bloom for brown rot and at petal fall to control shot hole will also reduce the spread of scab if appropriate fungicides are chosen.
The UC Davis info is usually quite reliable. They also list several possible fungicides, some of which are not available to folks without a pesticide license. The one I was able to find that homeowners can buy:
Chlorothalonil 720 SFT (Generic Daconil weatherstik) - 2.5 Gallon
The 2.5 gallon is available on Amazon, but probably way more product (and $$) than you need unless you have quite a few trees.
Here's a helpful guide for most peach/ nectarine problems:
https://extension.oregonstate.edu/catalog/ec-631-managing-diseases-insects-home-orchards#peaches-nectarines
Using the info from UC Davis above re sprays for brown rot, cross referenced with the table in the OSU guide, these fungicides might be appropriate:
captan, chlorothalonil, or propiconazole
Ive been hearing some people say they are having a hard time finding Captan, but you might already have some.
Changing the time of the sprinklers won't change much- you're watering at the best time, when the sum is about to come out and dry the leaves. is there a way to move the sprinklers so they aren't wetting the tree leaves?
You're also right that the frost may keep you from getting peaches this year- but I don't think that will make all the spores go away.
Here's some info from one of my disease diagnostic guides:
Twigs, leaves and fruit are infected, but the symptoms are most noticeable on fruit. The spores are overwintering in twigs and bark crevices. It's a good idea in future years, to do a dormant oil spray before the trees bud out in late winter. The dormant oil goes all over the branches and twigs- you want really good coverage. This product is least toxic environmentally, and smothers a wide range of fungal and bacterial residue as well as some insect eggs. It's too late for that spray this year, but it is the one preventative spray we can do in our home fruit trees that covers a lot of bases.
I hope you find this helpful! Let me know if you want clarification on anything. Best wishes, Nicole
