/diy/ - Do It Yourself

I moved into a new apartment this month and once every few days I'll find a cockroach in the kitchen near the sink. I've been incredibly clean with no food out, and it's always one or two. I think they are scouts. Yesterday I tried to kill one and it ran into the crack under the molding, making me think this is where they have always been coming from. You can see how it comes up slightly on the right side. There is an elevator shaft behind this wall. I figure if I can seal any holes in the wall then that should stop them permanently. But I'm a renter and the owners would almost certainly have a problem with me tearing out their dogshit work.

What's the solution here? Is there some kind of expanding foam spray I can squirt in there that will seal up the crack? I know this moulding is literally just a tube and the hole could actually be anywhere along the entire wall. Maybe if this hole were sealed they would start coming out around the sides of the floor cabinetry. I looked underneath the sink to check for holes and although I couldn't be sure I think it would be best to put something around all the pipes anyway. Like some kind of putty.

What should I do? Thanks. The owners suggested buying roach traps and being cleaner.