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Can you help me identify these insect cocoon? (If that’s what these are?) They are all over on our barns north side only. We want to know if they are pests and how to prevent them from returning. We are an organic farm so please keep that in mind when answering. #895657
Asked March 27, 2025, 6:02 PM EDT
Washtenaw County Michigan
Expert Response
Hi Liz, thanks for using Ask Extension.
It appears that these may be spent tussock moth cocoons which is where they lay their eggs to overwinter. The specific tussock moth is questionable but could be the White-Marked Tussock Moth. The larvae feed on a large variety of trees, both deciduous and coniferous, including apple, birch, cherry, elm, fir, hemlock, hickory, larch, oak, spruce, et al. They are known to place cocoons and lay eggs on buildings (especially under the eaves). Probably the best organic solutions are physical removal of eggs and cocoons, Bacillus thuringiensis var. kurstaki (Btk) and Spinosad. Neem has also been suggested. Check out the following link:
Hickory Tussock Moth Caterpillar
I hope this is helpful.
