Answer: In my experience, caterpillars would not change the foliage color. Foliage color can be affected by the weather, by the nutrients in the soil, and can also change as it ages from spring into summer. If you are worried about your tree, I would suggest you consult with your local Penn State county extension to see if it might be a good idea to run some soil tests and see if you need to make any adjustments there, or if they have other ideas as to why the foliage might look different this year. (You might take them a sample leaf or two along with a photo of the overall tree.) They should be able to help you with the tests and interpreting the results.
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