I studied lots on black widows in California.
Pesticides usually do not kill them. You need to eliminate their food source so they go elsewhere. This is done by using insecticide barriers on your own property.
Be sure to spray door jambs up about two feet as this is a favorite black widow hang out. Also, get some cheap white oops paint and use it everywhere you can: sheds, garages, etc. The contrasting color will cause the black widow to be easily spotted.
Last is charcoal capsules. Keep them on hand to help neutralize venom before you get to the ER. Can’t hurt and might help. Check this out on internet.