Black spots on pear leaves - Ask Extension
Hi, our three year old European pear tree had black spots on its leaves last Fall. What organic method should I use now if it's a fungus?
Also, ou...
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Black spots on pear leaves #866943
Asked May 03, 2024, 5:00 PM EDT
Hi, our three year old European pear tree had black spots on its leaves last Fall. What organic method should I use now if it's a fungus?
Also, our four year old peach tree has what looks like leaf curl. What is a good organic method? Thanks Rosa
Clackamas County Oregon
Expert Response
Hi Rosa and thanks for your questions about your peach and pear trees. Let's do the peach tree first.
Peaches are tough to grow in the Willamette Valley and you may find it's easier to buy your peaches. The only thing listed for home use is Ortho MAX Garden Disease Control at 3.75 teaspoons/4 gal water. You have missed the spray schedule for this crop, as you would need to spray two times: at 50% leaf fall (late October), and again at delayed dormant (usually in late February, before floral buds open). There is no organic method listed for home use, but you can call a licensed spray company as they have some organic products available to them.
The first step for the pear tree is to identify what is actually causing the black spots. This can be a fungus or a mite and we would need to see pictures to be able to diagnose and treat the problem. When you notice the spots this year, send in a picture and description of both sides of the leaves and we will have a better idea of what is going on.
And maybe there won't be spots this year!
Peaches are tough to grow in the Willamette Valley and you may find it's easier to buy your peaches. The only thing listed for home use is Ortho MAX Garden Disease Control at 3.75 teaspoons/4 gal water. You have missed the spray schedule for this crop, as you would need to spray two times: at 50% leaf fall (late October), and again at delayed dormant (usually in late February, before floral buds open). There is no organic method listed for home use, but you can call a licensed spray company as they have some organic products available to them.
The first step for the pear tree is to identify what is actually causing the black spots. This can be a fungus or a mite and we would need to see pictures to be able to diagnose and treat the problem. When you notice the spots this year, send in a picture and description of both sides of the leaves and we will have a better idea of what is going on.
And maybe there won't be spots this year!
Hi, thanks and here is a photo of pear spots.
.Best Rosa
Hi Rosa and I guess you'll have to try again with the picture. The system says it is too big and gave us an error message. If you can get a smaller file, it should send. Looking forward to your picture...
Trying again...thanks! :)
Hi, thanks and here is a photo of pear spots..Best Rosa
Hi Rosa and thanks for being persistent with the picture problem. It's a good thing you got such great pictures because I can easily tell what is going on. You have Pear Leaf Blister Mites. Here are two ways to control them based on Oregon State University research:
Management-biological control
Phytoseiid predator mites almost always keep mites under control if broad-spectrum insecticide applications are
avoided. Heavy rain and cold weather also suppress mite numbers.
(With our rain and heat this year, we seem to have more mites than usual, so I'm not sure the predators are able to keep up!)
Management-cultural control
Suppression of broadleaf weeds such as mallow, bindweed, white clover, and knotweed with cultivation or grasses may reduce mite numbers. Wash mites from the tree with a strong stream of
water. Water trees properly, as drought-stressed trees are more
susceptible. Avoid excessive nitrogen applications, as this encourages mites.
If you want to spray the whole tree, be sure the chemical has one of these active ingredients, all of which are organic:
horticultural oils
insecticidal soap
kaolin clay
sulfur
spinosad
Read and follow the directions EXTREMELY CAREFULLY, as the label is the law and more is not better where chemical sprays are concerned.
Good luck, Rosa, and now I'm going to go out and check my own pear tree!
Management-biological control
Phytoseiid predator mites almost always keep mites under control if broad-spectrum insecticide applications are
avoided. Heavy rain and cold weather also suppress mite numbers.
(With our rain and heat this year, we seem to have more mites than usual, so I'm not sure the predators are able to keep up!)
Management-cultural control
Suppression of broadleaf weeds such as mallow, bindweed, white clover, and knotweed with cultivation or grasses may reduce mite numbers. Wash mites from the tree with a strong stream of
water. Water trees properly, as drought-stressed trees are more
susceptible. Avoid excessive nitrogen applications, as this encourages mites.
If you want to spray the whole tree, be sure the chemical has one of these active ingredients, all of which are organic:
horticultural oils
insecticidal soap
kaolin clay
sulfur
spinosad
Read and follow the directions EXTREMELY CAREFULLY, as the label is the law and more is not better where chemical sprays are concerned.
Good luck, Rosa, and now I'm going to go out and check my own pear tree!
