Spots on Apple Tree Leaves - Ask Extension
My Apple trees are dropping around 20-30 yellow leaves a day (since last week), and when I looked up into the trees today I saw that the leaves had bl...
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Spots on Apple Tree Leaves #249932
Asked June 05, 2015, 12:28 PM EDT
My Apple trees are dropping around 20-30 yellow leaves a day (since last week), and when I looked up into the trees today I saw that the leaves had black spots all over them. I just bought this house last summer, so I don't know if this is normal. I suspect with all the rain in May it's a fungus, but I wanted to be sure. Can you tell me what we are dealing with here, and what kind of treatment I need? The worst tree is a Golden Delicious, and the other tree is Red Delicious.
Davis County Utah
Expert Response
Hello:
Actually, that is not a fungus, it is a mite. The mite is so tiny that you cannot see it with the naked eye; you would need a microscope. If you feel the leaves, you will notice that the "spots" are actually small "bumps" or blisters. Within each blister are hundreds of mites.
They are called appleleaf blister mtes. They are very common in Utah and will not harm the tree. They are prevented by applying the insecticide Sevin plus horticultural oil. You could try an application now to prevent further spread, but most of the mites are protected inside the blisters. The best time to treat is in late summer/early fall, when the mites migrate from the blisters to the buds.
I suspect that the leaves are yellowing and dropping because the tree is balancing out the root to leaf ratio. Most yellowing leaves should be on the interior of the canopy. You might consider a soil test to be sure there are no nutrient deficiencies.
Here is more information on blister mites and on the USU Soil Analytical Lab:
http://utahpests.usu.edu/IPM/htm/fruits/fruit-insect-disease/blister-mites-appleleaf-pearleaf/
http://www.usual.usu.edu/forms/index.html
Actually, that is not a fungus, it is a mite. The mite is so tiny that you cannot see it with the naked eye; you would need a microscope. If you feel the leaves, you will notice that the "spots" are actually small "bumps" or blisters. Within each blister are hundreds of mites.
They are called appleleaf blister mtes. They are very common in Utah and will not harm the tree. They are prevented by applying the insecticide Sevin plus horticultural oil. You could try an application now to prevent further spread, but most of the mites are protected inside the blisters. The best time to treat is in late summer/early fall, when the mites migrate from the blisters to the buds.
I suspect that the leaves are yellowing and dropping because the tree is balancing out the root to leaf ratio. Most yellowing leaves should be on the interior of the canopy. You might consider a soil test to be sure there are no nutrient deficiencies.
Here is more information on blister mites and on the USU Soil Analytical Lab:
http://utahpests.usu.edu/IPM/htm/fruits/fruit-insect-disease/blister-mites-appleleaf-pearleaf/
http://www.usual.usu.edu/forms/index.html
