I use Malathion. You can buy it concentrated or diluted at Home Depot. Find their tent early in the spring and in the morning. Saturate the tent with the malathion spray and that will take care of them. Be aware that they lay eggs sacks on the tree branches. You'll want to look for those when the leaves are gone in the fall. The are 1-1.5" crystallized oblong casings that surround a branch. Spray those too and then watch for any tent activity in the spring.