If you want to check an old tire, water feature or pond, etc. for larvae, it’s easy – just get a turkey baster, and a white container like an empty tofu container. To get difficult to reach places, just use a long, large straw on the end (these often come with the roach powder).
Then start sucking up water in suspicious places. Squirt it into the white container so you can easily see the larvae (which look like dark, long wiggling things) or the pupae (which look like small dark shrimp).
Just because you don’t find them does not mean they are not there. They can hide by swimming down to the bottom when you disturb them. You need to sneak up on them while they are swimming near the surface (where they breathe). If you disturb them, try sucking up water from just above the debris at the bottom.