You can find anti-rat sprays in most home department stores that may be worth a try. Spray them along fences and in areas where you don’t want rats to go (like around decks) and they may think twice before approaching. For a natural version, you can try a mint spray, since rats generally dislike mint. But even the most effective sprays are unlikely to stop a hungry rat over time.

Squirrels hate not having access to secure shelter or food sources. Your best line of defense is to make your property less attractive by removing access to these things. There are chemical squirrel repellents, but these have mixed success. According to Pennsylvania State University, you can apply products containing the bittering agent denatonium saccharide to a squirrel's favorite fence, tree, or roof spots. However, you need to reapply repellents regularly, which aren’t scientifically proven effective.

The most common wasps are hornets, yellowjackets, and paper wasps. Both hornets and yellowjackets are black and yellow, and hornets are known to be more aggressive if their nests are disturbed. Paper wasps are black or reddish-brown with yellow markings and often build nests on eaves or branches. Of the more than 300,000 species of wasps, these are the most often encountered by pest control professionals.

Squirrels hate anything that disturbs the peace in their nest. Loud noises, bright lights, and strong smells like cayenne pepper or mothballs will deter them from your attic. Spread these scents, add a strobe light, or use an ultrasonic repeller to keep squirrels from nesting in your attic.