Really prolific this summer are the caterpillars known commonly as webworms. Common infestations in ornamental crabs and cherries (as well as other species). We get asked several times a day to remove theses from people’s trees. We are not able to do so, as it’s just too many requests, and a lot of times not necessary. Webworms are messy and do look like they are killing your tree. Instinct for most is to cut out the affected branch. Which yes gets rid of the mass of caterpillars but you’ve also just lost your branch. It’s important to know that they rarely kill the branches, and an infestation this year doesn’t mean you’ll have it worse next year. They soon stop gorging on your tree’s leaves and eventually become moths. Who fly, mate and lay eggs(maybe back in your tree or maybe somewhere else).
For my two trees at home, I knock out the lower nests with a pole pruner (try and wrap the web mass around the blade and pull them out). The caterpillars usually group together in a mass and easy to locate within the webs. I then put them in the garbage. The higher up ones I leave. The webs are visible over the winter and break down the following spring. In my experience the affected branches have always have survived. So please don’t hack your trees because you have a bug. You could be worse than the leaf munchers.