Random science lesson of the day... One of the things that you learn when you're involved in plant science is the "disease triangle".

After a while you also realize it applies to pets and humans as well. Whether it's West Nile, Parvo, fleas, ticks, heartworms.... There are three factors that contribute to an outbreak of disease or pests/parasites. You have to have the pathogen or pest, the host (and a vector if the disease is transmitted by something other than the host) and a favorable environment. They all have to be present in the right amount or you don't have the problem. Outside of that magical combination you never reach critical mass, and you don't have the disease or the pest never becomes an issue. So the key to controlling an outbreak or infestation is to alter the contributing factors to break the triangle.

This year our magical combo has been perfect for fleas. We can't get rid of the hosts and our control over the environment is limited so we have to focus our integrated pest management strategies on the pest itself, and what little environmental control we do have via lots of lawn mowing, flea treatments for the house and dogs, frequent bedding washes, and diatomaceous earth where we can use it. It requires a holistic plan of attack with coordinated application of the various control methods to get ahead and stay ahead of the problem.
Something to think about the next time you have a disease or pest problem in your home or garden....