Oak Loopers Defoliating Michigan Oak: Natural Cycles, Little Control Possible

Thousands of green worms on webs dropped from a giant oak in mid-October, pupated in white cocoons everywhere. Similar event 5 years ago. Tree lost half its leaves early.

Expert: Oak looper caterpillars. They can heavily defoliate but trees recover unless repeated yearly. Pupae on ground emerge as moths next spring/summer to reinfest. Natural enemies often reduce next year's numbers. No practical treatment for large trees. If oak is already declining, loopers add stress.