Although more than 2,000 flea species exist, the cat flea causes the most problems for both cats and dogs in the United States. These nuisance insects frequently cause itching, irritation and rashes in pets and people, and some even transmit tapeworms or diseases, including typhus, tularemia and the murine plague. You can treat your pet with a preventative monthly flea medication, but you must also treat your yard or you will likely experience a re-infestation. Fortunately, you can treat flea problems in your yard using organic, cultural and chemical control measures.

Cat and Dog
credit: vvvita/iStock/Getty Images
Blood-sucking fleas thrive outdoors in spring and summer.

About Fleas

A flea's life cycle lasts between 28 and 42 days, but one female flea can lay thousands of eggs in that short time frame. Adult females lay eggs on host animals, and the eggs fall to the ground to hatch in two to five days. Fleas thrive in moist, shady outdoor areas and temperatures that fall between 80 and 90 degrees Fahrenheit. Flea larvae can't survive in areas that receive direct sunshine. When treating outdoor spaces for fleas, keep in mind that the larvae typically stay within 50 feet of your dog's or cat's favorite shady resting spots. This might include beneath bushes or trees, along a fence or wall, in flowerbeds or gardens, under porches or decks or around a doghouse, kennel or dog run. Focus your flea control efforts on those locations for optimal results.

Diatomaceous Earth

Diatomaceous earth, a powder made from the crushed shells of small aquatic creatures called diatoms, is a natural treatment that effectively kills fleas in your yard. The tiny pieces of shell are completely harmless to people and animals, but they scratch a flea's exoskeleton, making the pest die of dehydration. Lightly sprinkle food-grade DE powder on the soil's surface in shady lawn areas where your pet likes to hang out. Repeat treatments every seven to 10 days until the pest problem comes under control. Renew DE powder after a rain or heavy dew because the substance only works when it's dry. Wear a face mask and protective eyewear when applying DE powder to avoid breathing the dust or getting it in your eyes. Keep pets and people inside until the dust settles.

Beneficial Nematodes

Beneficial nematodes are microscopic roundworms that prey on fleas in the larvae and pupae stages. They enter a flea's body and release a bacterium that kills the pest in less than 48 hours. Despite being lethal to fleas, nematodes won't affect pets, people, beneficial insects or plants. Beneficial nematodes are available at garden centers. Look for Steinernema carpocapsae nematodes if you reside in a cool area, and Steinernema feltiea nematodes if you live in a warmer climate. Beneficial nematodes come in various formulations, including sponges, granules or gels. Following the label's instructions exactly, use a garden sprayer to spot-spray nematodes in the problem areas of your yard. Beneficial nematodes require moisture, so give the treatment areas about 1/4 inch of water before and after application. Avoid spraying in direct sunshine because nematodes are sensitive to heat and light. Instead, spray in the late evening or early morning when the temperature falls between 60 and 85 degrees Fahrenheit.

Spot Treatments

Because fleas don't typically rest in sunny, open lawn areas, you can often kill outdoor pests by using a carbaryl-based insecticide to spot-treat just the shady areas where your pet likes play or sleep. Carbaryl products come in various formulations, including an easy-to-apply granule form. Following the manufacturer's instructions, spread 4 to 9 pounds of granules for every 1,000 square feet of treatment area. Lightly water the treated spots after application to activate the chemicals. Apply a second treatment in seven to 10 days to catch any new fleas. Don't allow people or pets to enter treatment areas until the watered-in spots completely dry. Apply only on calm days when no rain is expected for at least 24 hours. Wear protective clothing and eyewear to avoid contacting the potentially irritating chemicals.

Broadcast Sprays

On occasion, severe flea infestations can occur in sunny, open lawn areas. Applying a broadcast insecticidal treatment can reduce the risk of bites to your pet and family members. Permethrin-based pesticides work well as a broadcast treatment, but carefully read and follow the manufacturer's instructions. One product recommends mixing 2 1/2 to 5 teaspoons of concentrate with a gallon of water. Use a handheld sprayer to evenly apply the solution over your lawn. Treat the area again in seven to 10 days to kill newly developed adult fleas. You might need to make as many as four applications to control severe infestations. Spray in calm weather when no precipitation is predicted for the following 24 hours. Wear protective eyewear and clothing, and keep pets and people out of the area until the spray thoroughly dries.

Outdoor Bug Bombs

If you only need relief for a short time in a small area and prefer not to use conventional sprays, outdoor bug bombs, also called foggers, should do the trick. Look for a ready-to-use fogger containing cyfluthrin for effective results. Following the instructions on the label, stand about 5 feet away from the target treatment area and spray about 12 inches above the ground so the spray can drift and settle into the area. Spraying on calm days offers the best results. Keep pets and family members out of the treatment area until it dries and wear protective clothing, goggles and a face mask to prevent chemical exposure. Cyfluthrin is toxic to aquatic creatures, so don't use foggers near bodies of water. Bug bombs act quickly but only affect insects inside the treatment area for six hours tops.

Cultural Control Methods

Cleaning up your outdoor landscape increases the exposure of fleas to both sunlight and insecticides. This means keeping the grass mowed short, raking your entire yard, pruning low-lying bush branches and removing organic debris from beneath shrubs and in flower beds. Fleas are repulsed by cedar, so consider using cedar mulch in your flower beds, border areas, pet runs and your pet's favorite playing and resting spots.