Gypsy Moth Alert

October 2019:

Gypsy Moth Alert

Based on my own observations and feedback from several lake residents, we can expect a fairly heavy gypsy moth infestation next year. The distribution of the tell tale egg masses does not appear to be uniform in the area. To determine how much of a problem it might be on your property, examine your trees, underbrush and other hiding places such as woodpiles, rocks, branches on the ground and even outdoor equipment such as wheelbarrows and gardening tools. I discovered an egg mass on one of my gas cans while filling it at a gas station.
You can start controlling the infestation between now and the emergence of the caterpillars next April by destroying the egg masses and then follow up with measures to control the caterpillars next spring. Control agents like Bacillus thuringiensis kurstaki can provide an effective control of the caterpillars however, finding a reliable source may be a bit of a challenge. One can also hope that we have a good population of a small wasp (Encyrtidae family) that preys on the caterpillars. Gray Merriam, PhD, DSc, our resident ecologist and who reviewed these notes, points out that in the longer term, a new pathogen holds the promise of controlling gypsy moth populations here as it already does in the New England states. See the Cornell U publication below.

I have dealt with several previous infestations both at the cottage and at our home property mainly by spraying the egg masses with Pinesol, a widely available heavy duty household detergent. I fill it undiluted into a window cleaner bottle. The spray nozzle can be precisely aimed and is easily triggered. Pinesol was recommended by Ontario forestry staff when I first dealt with an infestation in the 1980s. The govt guide lists a variety of pesticides you may be able to find in specialty stores.

Scraping the egg masses is also effective but time consuming if done properly and not very practical when attempting to scrape from rocks and other low lying objects like fallen branches. Inevitably, some eggs will fall to the ground and they can still hatch.

For additional information on the Internet go to: a one pager that does not really have good practical control information - contains some practical control information an older guide published by the federal government with detailed information about the various life stages of the gypsy moth, its impact on the environment and control measures. Educational but, in my opinion, not very helpful for homeowners with relatively small properties. and - albeit from Wisconsin, good background reading and practical advice on how to deal with the problem.

Bernie Dertinger