I have a hydrangea standard in my south-facing front garden and this morning I noticed a couple of clusters consisting of a gauzy “web” each containing a LOT of what look like small, thin and each about 3/4″ to 1″ long, busily apparently eating the leaves to which they’ve attached these webs or tents. I am wondering if these are tent caterpillars or something else, and since they (so far) only seem to be in a couple of places, can I just cut out the webs and worms and put them in the garbage? Do I need to spray them with something instead, or after cutting them out?? Many thanks in advance for your help!!
Hello, thank you for reaching out to the Toronto Master Gardeners for help with your Hydrangea. It does sound as if your hydrangea is infested with tent caterpillars. I am attaching a link to the University of Minnesota’s website which has several photos that can assist you in confirming the culprit. Note that the website suggests pesticides which we do not recommend. My suggestion would be to carefully remove the web including all the caterpillars and other debris and if possible to safely do so, burn it. This is most safely done in a large metal garbage can.
https://extension.umn.edu/yard-and-garden-insects/eastern-tent-caterpillars
The Government of Canada has an excellent website and photos on tent caterpillars as well as how to control them.
Good Luck!