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Maple tree turning red in July/holes in leaves #842389
Asked July 24, 2023, 4:18 PM EDT
We have two young maple trees (almost 3 years old) that were doing well this spring and I am now noticing that the leaves are turning red on the top of one and most of the leaves have holes in them on both trees. Upon closer inspection I also noticed some sort of large insect on several of the leaves of one and yellowish powdery clumps on the trunk of the one with the red leaves. I am hoping it is not too late to help them. Could you please give me some guidance on how we can treat them? I am attaching some pictures. I have more pictures showing the holes in all of the leaves. This only allowed me to upload 3 pictures. f you need better pictures or additional information, please let me know. Any guidance you could give me would be very much appreciated.
Dutchess County New York
Expert Response
Here are some more pictures:
Hi Cathy,
Thank you for your question. We noticed 2 issues with your maples: Spongy moth and Tar spot.
For the spongy moth, in the lifecycle of the spongy moth, it is the time to scape the egg masses into soapy water and let them masses soak for at least 24 hours. Spraying could be done in the Spring but has drawbacks in addition to the timing. The insecticide Bt (Bacillus thuringiensis) is effective when a caterpillar ingests the leaves on which it is sprayed. So first a tree’s leaves needs to be totally covered which is hard for a homeowner (we don’t have the equipment). Next it kills any caterpillar which ingests it. Our native oaks support over 350 species of caterpillars besides spongy moths. Commercial pesticide applicators can treat large trees but the impact is beyond just the spongy moth. Finally, young caterpillars move in the wind (it’s called ballooning, on a strand of silk) and the adult moths fly. So spraying trees in one area does not provide total control the next year as they move.
The burlap is a good option. And knowing that trees and shrubs will re-foliate. Their strength is in their trunk and roots.
If you have small or younger trees/shrubs you may want to give them a deep watering. A slow hose running 30 minutes or so works well. Or take a large 10 gallon bucket drill a few holes in the bottom, place it at the plants, fill it with water and walk away.
If we have little rain, do it again in a few weeks.
A description of the pest and suggestions for control are in this fact sheet. https://nysipm.cornell.edu/whats-bugging-you/gypsy-moths/ Burlap banding the young and/or special trees and also any nearby oaks is probably the most effective. (Young spongy moth larvae feed mostly during the day. Older larvae usually feed at night, then move down the tree to hide in bark crevices, leaf litter or other dark, protected locations during the day. The banding catches them as they move back up the tree to feed.) Trap detail is at this link https://cornell.app.box.com/s/faqiigyjtwpcngha0au6du8yd0m6emiv
For the tar spot, be sure to rake up and destroy the leaves in the fall.
http://plantclinic.cornell.edu/factsheets/tarspotofmaple.pdf
Please let me know if you have any additional questions.
