Treating fleas means breaking the flea life cycle using a targeted IGR that tackles the larvae.


A big flea season is driven by warm, humid weather as these are the ideal conditions to maximise the survival of flea larvae. This year has been a big flea season! Understanding a bit about flea larvae helps to make good decisions about product choice and application areas when carrying out a flea treatment.

When inspecting for fleas, whilst adult fleas are relatively easy to see, the flea larvae are a lot more secretive. These translucent, hairy worm-like larvae (main picture, above) are around 1.5 mm on hatching, growing to about 5 mm before they are ready to pupate. Apart from their small size, they are difficult to see as after hatching they quickly move away from light and burrow into the substrate.

Flea larvae don’t get to choose where they live. Flea eggs easily fall off their host and are distributed wherever the pet goes, so will be most concentrated in the areas where the pet spends most of their time resting. Fortunately for the flea larvae, these places tend to be cool and dark – just the type of places they will thrive. Although flea larvae need at least 75% humidity, the substrates in which they live need to be dry and protected from rainfall.

The main hot spots for fleas will be in the pet’s resting places such as bed bedding, flooring, carpets, furniture, outdoor shady areas and subfloors. The flea larvae will develop in these areas, eating organic material including ‘flea dirt’ – flea faeces containing partly undigested blood. It takes about 15 days for the flea larvae to progress from the egg to the pupal stage.

Although a veterinary pet treatment and a thorough vacuum and clean are important elements of a comprehensive flea treatment, success requires that all areas where the pet has visited are also treated, with a particular focus on the pet resting areas. Have a chat with the owner and ask them to point out their pet’s favourite hangouts. Whilst pet bedding and some furnishings can be washed to eliminate fleas, other areas will need an insecticide treatment. Although flea larvae are susceptible to adulticides, the areas to be treated should be considered sensitive locations due to their use by pets. This means using a larvicide, an insect growth regular (IGR) such as Sumilarv, is a smart choice.

Sumilarv (pyriproxyfen) works on all stages of the flea life cycle. In addition, it doesn’t just break the breeding cycle by controlling the larvae when they moult, it has actually been shown to kill the larvae. Importantly it is also active on the late stage larvae, which means that even if they pupate, they don’t develop into adults and die in the cocoon. With its long residual performance (up to 12 months in carpets) and stability under UV light, it is ideal for indoor and outdoor applications.

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