What pest is damaging my crabapple tree? - Ask Extension
Hello! I am a new homeowner in Hillsboro who is trying to restore a very neglected crabapple. It is quite damaged with what looks to me like spider mi...
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What pest is damaging my crabapple tree? #802371
Asked July 21, 2022, 5:32 PM EDT
Hello! I am a new homeowner in Hillsboro who is trying to restore a very neglected crabapple. It is quite damaged with what looks to me like spider mites. (see photos!) The leaves are mottled yellow with brown edges. Many have fine white webbing on them. I also see a lot of little critters: they are pale beige and have a small head with a comparatively large tear-drop shaped abdomen. What can I do, if anything, to save this tree?
Thank you!
Washington County Oregon
Expert Response
Crabapple trees are prone to numerous issues. See EB 1809 from WSU. Do you know which cultivar you have? Here is a table of crabapple susceptibility to common disease, from the Extension Service PNW Handbook.
Provide more photos of the tree overall, and a more distant view showing the neighboring plants and growing situation. Share all you can think of about how you are caring for it and other things, like sun exposure and drainage. How long has it been unhealthy?
Provide more photos of the tree overall, and a more distant view showing the neighboring plants and growing situation. Share all you can think of about how you are caring for it and other things, like sun exposure and drainage. How long has it been unhealthy?
I will be unavailable for awhile, and other experts can assist you. I’m responding now, though, with information about crabapple spider mite and Aphid from the Extension Service PNW Handbook. Follow the links on these pages, use a magnifying glass to see pests on leaves clearly, and ask any follow-uo questions here.
The Metro Master Gardener Volunteers are also available. Sometimes a direct discussion rather than this delayed web forum, is easier when problems are complicated.
The Metro Master Gardener Volunteers are also available. Sometimes a direct discussion rather than this delayed web forum, is easier when problems are complicated.
Hi Jacki,
Thank you for your response! I appreciate the links you sent.
I looked at the pests under a microscope and even got a few photos (attached). To me, they do NOT look like either spider mites or aphids! Eep!
Although I don't know the cultivar, I think my crabapple seems closest to Sentinel. It seems to have an upright/upright spreading habit (although I think it's terribly overgrown?), and pale pink flowers that appear in early to mid-April. I've attached a photo of the tree from a snowy April 11 of this year.
The tree does not have any neighboring plants, and it grows in full sun on the northern lawn of our house. We bought the house over winter, and I only started watering the crabapple about two weeks ago—too late, maybe?—and now I water once a week. I'm not sure what kind of drainage it has. The soil here seems to have a lot of clay in it.
Any help would be appreciated! Let me know if it would be easier to call or even come in the to extension office off Cornell with a leaf sample.
Thanks,
Anne 
Hello Anne,
The stippling damage and webbing describes spider mite damage: https://pnwhandbooks.org/insect/tree-fruit/apple/apple-spider-mite
Any of pesticides listed for Spring and summer could be applied at this time. Read and follow the safety instructions. Some insecticides can damage plants when applied during hot weather.
In terms of the other insect and damage looks most like an an aphid to me (soft exoskeleton, long antennae, horizontal stripes). They also cause stippling damage and leave messy residue. However, the shape and color don't match the aphids shown here very well: https://pnwhandbooks.org/insect/tree-fruit/apple/apple-aphid
Here's more about aphids: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7404.html
Aphids come in many shapes and colors.
None of the other insects here match perfectly either: https://pnwhandbooks.org/insect/tree-fruit/apple
Regardless, the insecticides listed for summer use on the spider mite or aphid page will control all insects on the leaves, provided you get good coverage.
The stippling damage and webbing describes spider mite damage: https://pnwhandbooks.org/insect/tree-fruit/apple/apple-spider-mite
Any of pesticides listed for Spring and summer could be applied at this time. Read and follow the safety instructions. Some insecticides can damage plants when applied during hot weather.
In terms of the other insect and damage looks most like an an aphid to me (soft exoskeleton, long antennae, horizontal stripes). They also cause stippling damage and leave messy residue. However, the shape and color don't match the aphids shown here very well: https://pnwhandbooks.org/insect/tree-fruit/apple/apple-aphid
Here's more about aphids: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7404.html
Aphids come in many shapes and colors.
None of the other insects here match perfectly either: https://pnwhandbooks.org/insect/tree-fruit/apple
Regardless, the insecticides listed for summer use on the spider mite or aphid page will control all insects on the leaves, provided you get good coverage.
Weston Miller (he/him)
Associate Professor (Practice)
Oregon State University
OSU Extension Service | Department of Horticulture
<personal data hidden>
Hi Weston,
Thank you so much for your email! I didn’t realize that aphids can come in such a wide range of shapes, colors, and sizes!
I’ll move ahead with a summer spray.
Best,
Anne
