Liz, the pills are used here as well by some vets, for dogs too. Other vets recommend the dab on material (also good for ticks and other parasite besides heartworm). The first application must be early in the season, one month before the fleas come out.

I agree with Stilly River Sage. The toxins kill desirable insects, and are bad for the squirrels and birds and bumblebees that feed and nest in the yard.