It could be a praying mantis egg sac -- look up some pictures. They are the good guys.

Scott

What you have is Tent caterpillars. They usually hatch out about the time forsythia blooms here in Virginia Zone 7. You can wait until they hatch and are small and crawling around, before they build their tents, and spray with a pesticide that is registered for your fruit trees. I am guessing you pruned the branches off a fruit tree. Once they build their tents (in the crotch of trees) you will have to penetrate the nest to get at them.

If it is tent caterpillars I take a propane torch and tape it to a broom handle and scorch them. No spray but be carefull not to hurt the bark. Here we fire prune blueberries so I know plants can take it hot if it is short term.

Bacillotoxin is a lot safer than torching them. It's organic, sold under the name of Thuricide and BT (and others). It's a bacillus that only infects the larval (caterpillar) form of moths and butterflies. Doesn't harm or affect anything else. Spray at the first sign of webs and you won't have a problem for a month or more.