That's not a giant spider in your tree - it's the fall webworm!

What to Look for: In late summer and early fall, large nests appear on the ends of branches of many types of trees. Pecans seem to be a favorite. Nests are full of tan caterpillars with long, silky hairs. They eat every leaf within reach, continually building larger webs until late autumn, when they pupate. The webs resembling dirty rags and are unattractive in the landscape. On most trees they are not a problem, but fruit and nut trees can be affected adversely.

What to Do: Remove nests by hand. Do NOT burn nests. Encourage predators and parasites like paper wasps, yellow jackets and brown stink bugs. Apply Bacillus thuringiensis (Bt) when larvae are small. Lightly wet nest and cover nearby leaves with a labeled insecticide such as carbaryl. It is not necessary to soak leaves till they drip.