Why Fleas Come Back in Your Florida Yard

The adult fleas on your pet are the only stage of the life cycle that lives on your pet. Everything else — eggs, larvae and cocoons — is off the animal, in the fibres of your floor and in the shaded ground of your yard. That is the whole reason fleas come back after what looked like a successful weekend: the visible adults were a small fraction of the population, and the rest of it was never on the animal to begin with. UF/IFAS puts it in one line: removing fleas from the animal alone is futile.

Where the other stages actually are

A female cat flea lays eggs at a rate of up to one an hour, and the eggs are dry and smooth enough that they roll straight off the coat. They land wherever the animal goes: the bed, the rug, the sofa seam, the car mat, the patch of dirt under the hedge. Larvae hatch within about two days and feed on organic debris in the floor covering, mostly the dried adult flea faeces that fell with them. Then the larvae spin silk cocoons, and the sticky outer surface of the cocoon picks up dust and debris until it is effectively camouflaged.

The cocoon is why the timing feels random

Adults stay inside the cocoon until they are fully developed, and UF/IFAS notes they are stimulated to emerge by vibration or a rise in carbon dioxide — in other words, by something warm-blooded walking past. That is why a house shut up for a week can produce a burst of fleas on the day you come home, and why a yard that seemed fine gets busy the afternoon the children play on it. The population was not growing. It was waiting for a cue.

The yard reservoir is not the lawn

This is the part that surprises people. Flea larvae avoid rainfall, irrigation and sunlight, and they develop where relative humidity is at least 75 percent and the temperature sits roughly between 70 and 90 degrees. An open, sunny, irrigated lawn is a poor flea nursery. Protected shade is an excellent one — and it is exactly where a dog chooses to lie down.

• The cool hollow a dog digs out under a shrub in August.
• Under the deck, the porch steps and the shed — dry, shaded and undisturbed.
• The mulch bed along the fence line and beneath a thick hedge, where the ground never sees sun.
• The crawl space, the carport corner and the side yard nobody walks through.
• Indoors, the same logic: under furniture, along the baseboard, and in the pet bed rather than the middle of the room.

The traffic you do not control

Fleas also arrive on animals that are not yours. UF/IFAS lists controlling the access that feral cats, opossums and raccoons have to a yard as part of flea management, because those visitors restock the shaded ground each time they pass through. If bowls are left outside, fruit drops and a bin lid does not close, the property is an attractive stop — and no amount of work indoors changes what is bedding down under the deck at night.

What UF/IFAS says does not work

• Flea combs remove somewhere between 10 and 60 percent of the fleas on an animal. That makes them a detection tool, not a control method.
• Ultrasonic devices are described as not very effective at moving an established population.
• Dietary vitamin B, brewer's yeast and garlic are reported to be of little value in the scientific evidence.
• Cedar chips and wax myrtle leaves have repellent properties according to some homeowners, but that has not been demonstrated scientifically.

What genuinely helps while you sort it out

• Vacuum floors, rugs, the edges of the room and under the furniture, and empty the vacuum outside. It lifts eggs, larvae and the dried flea dirt the larvae eat.
• Wash pet bedding hot and dry it hot, and do the throw rug the dog actually sleeps on rather than the one you think it does.
• Open up the nursery: rake out the deep shaded litter, thin a hedge so light and rain reach the ground, and block off the gap under the deck or the shed once you are sure nothing is living there.
• Take the bowls, the fallen fruit and the open bin off the yard so the wildlife route dries up.
• Whatever goes on the animal is a conversation with your veterinarian, not with a website and not with us. If the pet is scratching, that call comes first.

Why flea work runs on a schedule

Because of the cycle length and the stages a single application does not reach, flea work is a sequence rather than an event, and the house and the yard have to be handled together with whatever your veterinarian has the animal on. Skip any one of the three and the other two are re-seeded from it. Rhino treats fleas and ticks across the Treasure and Space Coast, and the inspection is free — including telling you plainly if what is biting is not fleas at all.

For the full picture of what we treat and where, see flea and tick control, the flea and tick control page for Melbourne, or the identification page for the cat flea. The estimate is free.

Source: the University of Florida IFAS Extension Featured Creatures profile of the cat flea.