Insecticides that kill adult fleas contain a chemical called permethrin. This chemical kills the fleas that bite but does little to control the larvae or eggs. The eggs, larvae and pupae are killed by a growth inhibitor that keeps the eggs from hatching and stops the juvenile fleas from developing into adulthood. Treatment of one stage and not the other stages of growth results in a re-infestation as the eggs hatch and the fleas grow.
For complete extermination, the best commercial flea killer contains a formula that affects all stages of growth and maturity. Choose a treatment that contains permethrin and a growth inhibitor such as Pyriproxfen. Methoprene is also a growth inhibitor but tends to break down quickly. Pyriproxfen breaks down more slowly and works better for outdoor use. Most applications of insecticide will need to be repeated in two to three weeks after your first round. Remember to water your grass after each application.
What Can I Do?
Keep Your Lawn Dry: Fleas thrive in moist places, so do not over-water your lawn. You’ll create a flea-friendly breeding ground for the these parasites.
Use Cedar Chips Decoratively: Given fleas’ aversion to their smell, try incorporating cedar chips decoratively so they have a permanent place in your yard.
Consider Planting Pennyroyal: Pennyroyal, also known as fleabane, naturally repels fleas once it’s fully established in your yard. This plant is a member of the mint family, and fleas do not like its scent. Use pennyroyal with caution, as it is toxic to cats if ingested, and is not recommended around pregnant animals.
Prune, Trim, and Mow: A sunny yard is not an ideal habitat for fleas as they cannot tolerate hot sun for long periods. Frequently mowing your lawn exposes the soil to sunshine, keeping it dry and flea-free. You can also prune bushes and trim trees to increase the sunniness of your yard, and keep fleas out.