Use bug bomb(s) first to kill the existing spiders. Then apply permethrin diluted with water to a 0.5% solution, spraying at all entry paths to the garage, edges, and dark areas.
The idea is to not just prevent spiders from returning. It’s also to deprive them of a reason to return by removing their food supply. Permethrin is a wide-spectrum insecticide and repellant. It has very low toxicity to humans, most mammals, and birds. Not good around cats or fish. It has good persistence (6-8 weeks).
Use bug bomb(s) first to kill the existing spiders. Then apply permethrin diluted with water to a 0.5% solution, spraying at all entry paths to the garage, edges, and dark areas.
The idea is to not just prevent spiders from returning. It’s also to deprive them of a reason to return by removing their food supply. Permethrin is a wide-spectrum insecticide and repellant. It has very low toxicity to humans, most mammals, and birds. Not good around cats or fish. It has good persistence (6-8 weeks).