They’re ugly, but not harmful to flora.
Those tent-like webs covering so many trees in Dufferin are called Fall Webworms and are created by nesting caterpillars.
The webs are most conspicuous in August and September but their unsightly webs, consisting of excrement, dried leaf fragments, and the cast skins of the larvae, don’t hurt trees.
If you’re adamant about removing fall webworms, cvc.ca has additional information.
