When it comes to homemade termite killers, there are a few options that can be effective in controlling termite infestations. One of the best homemade solutions is a mixture of boric acid and water. Boric acid is a natural compound that is toxic to termites. To make a homemade termite killer using boric acid, mix one part boric acid with ten parts water. Apply this solution to termite-infested areas or directly onto wooden surfaces using a sprayer or brush. The boric acid solution acts as a stomach poison for termites, ultimately leading to their elimination.