Spider infestation in outdoor shed

Hi all, we have rented out one of our apartments in Toronto and they vacated it last month. We moved into the apartment now and found that the previous occupants have not properly maintained the house. I turned my attention to the outdoor shed and found that the previous owners have left behind a lot of stuff there. Mostly cans and bottles of various things, insecticides, paint etc. That is okay, but they also left behind around a large population of spiders. I would like to get rid of them or reduce their number to a manageable level.

Which is the surest way to make that happen?