1976

Hello Carole,

It usually takes around 8 weeks after treatment before fleas completely disappear. The problem stage is the pre-emerged adult. After pupating, adults can stay quiescent in their cocoons for an extended period of time. They can remain in this sleep-like state for up to 5 months. However, they’ll rapidly emerge when they detect a host (heat and pressure).

Vacuuming regularly is the best way to force these pre-emerged adults to emerge. The vacuum creates heat and physical pressure on the carpets (where fleas develop), simulating host cues and triggering emergence. The vacuum cleaner will then suck the fleas up.

Immature fleas, including pre-emerged adults, usually aren’t significantly affected by carpet treatments, which is why you’re still seeing fleas. Sprays can’t penetrate carpets well enough and adulticides have a short-lived effect. Spraying Indorex probably won’t do much to speed up the eradication process. However, the insect growth regulator (IGR) contained within it, pyriproxyfen, will prevent re-infestation for 7 months. Any new eggs falling onto IGR-treated carpets won’t be able to survive.

That said, without pets there shouldn’t be any new eggs anyway, as fleas can’t reproduce on human blood. The exception is if you’re dealing with human fleas (P. irritans). This is a more rare species, and unfortunately my knowledge isn’t as extensive as with cat fleas (C. felis) dog fleas (C. canis). If the previous tenant had pets, then you’re likely dealing with dog or cat fleas.

If you choose to do further treatments, Indorex should be safe to spray. Indorex contains compounds that are considered safer than traditional insecticides like organophosphates and carbamates. In fact, it’s probably much safer than Ficam. The active ingredient in Ficam is bendiocarb, a carbamate insecticide. You may want to look into this compound a little bit. The company voluntarily suspended sales in the USA, because of safety concerns and unwillingness to do further toxicity studies to satisfy the EPA’s guidelines. Here’s the bendiocarb Wikipedia page.

The active ingredients in Indorex are permethrin, pyriproxyfen, and piperonyl butoxide. Pyriproxyfen is an IGR. It acts on the insect endocrine system by mimicking natural insect hormones that regulate molting. As such, it’s considered safer than most insecticides. Piperonyl butoxide is a synergist. It doesn’t have any insecticidal properties, but boosts the potency of pyrethrins (such as permethrin). As a result, less permethrin needs to be used in the formula, which leads to a safer a cheaper product. Permethrin is a pyrethroid compound. Pyrethroids are synthetic derivatives of pyrethrin, a botanical insecticide sourced from Chrysanthemum flowers. Pyrethroids are altered to achieve certain properties, such as being more photostable so they don’t degrade as quickly as pyrethrin.

Warm regards,
Adam