Wilson One Shot Jet Foam Hornet & Wasp Killer is a product that will quickly and effectively kill hornets and wasps. It is a foam spray which forms a cover over hornet and wasp nests. Effective for nests built in cracks and crevices and that are hard to reach. Its powerful jet spray allows for application from a safe distance. Nests should be sprayed late in the evening or early in the morning when the insects are resting inside their nest.