Bifen IT. I buy it on ebay. Lasts several months, relatively "safe". We use it around the house perimeter spring and fall, as we have had a huge problem with yellowjackets nesting, and carpenter bees boring. It has virtually eliminated insects in and on the house. Neighbor has a barn wing which houses a woodpile and a couple years ago it became infested with bumblebees....to the point he can hardly access it April-October. Sprayed lightly around the inside of the wing last week, and two days later he said the bumblebees were gone. All they have to do is walk through it or on a surface sprayed with it.