Where should I fight fleas, infested basement or flea-free upstairs with old carpeting

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QuestionsCategory: Flea InfestationsWhere should I fight fleas, infested basement or flea-free upstairs with old carpeting
CrazyCatLady asked 3 months ago

Thank you for this wonderful website!
I have a flea infestation in my basement!  I have two 11 year-old cats, 1 male, 1 female, and a female about 2-1/2 years old. I have a small 2-bedroom home with a full basement where I keep the litter boxes.  The cats have been living there since mid-June when I first discovered the fleas.  No fleas upstairs.  My cats have Revolution on them and I have been cleaning the basement with broom, lint-tape and canister vac. Yet, the fleas persist.  The source was items I am storing for a friend.  Those items are now sealed in black, plastic bags.
I recently read on this website that fleas thrive in high humidity and die off with 50% or less humidity.  My basement is unfinished, cement, and has an open drain. To control sewer gas the drain has an insert that must be kept full of water.  My upstairs is carpeted.  However, the carpet pile is about gone.
Do you think I would be better off to bring the cats upstairs to fight the fleas? I would spray Knockout on carpet and furniture (residual of 7 months), wash couch covers, etc. and vacuum. With cold weather approaching the furnace will be on causing dryer conditions throughout the house, but especially upstairs. And, the cats will have a smaller area. My bedroom and bath are off-limits to the cats.
Also, in either case, how can I eliminate the fleas from my basement? Fleas, eggs, larva and pupa have SO many places to hide!
Thank you for your advice!

1 Answers
Adam Retzer Staff answered 2 months ago


It probably doesn’t matter much where you move the cats to while you control the fleas. It’s actually somewhat beneficial to allow pets access to where the infestation developed. The cats will go to their usual resting places, which are the flea hot-spots. This will cause the adult fleas to emerge from cocoons (heat and pressure trigger emergence), and then jump onto the treated cats and die. So, it can help speed up the eradication process. If the cats weren’t there, some of the cocooned fleas could enter a quiescent state for up to 5 months (they still could even with the cats there, but more would be triggered to emerge).

Inside homes, the humidity factor doesn’t really matter all that much. It will be near-ideal everywhere. Fleas develop in dark, protected micro-habitats that have their own micro-climate that’s kept fairly regulated compared to surrounding conditions.

The Knockout will work on the cement. Pyriproxyfen (Nylar) is the most important ingredient. It’s an insect growth regulator that stop eggs and larvae from developing for 7 months. There has been a study showing that it is effective on concrete and other materials.

Yes, the immature stages have many places to hide. But, if the cats are treated, the problem should resolve in around 8 weeks. They shouldn’t be able to reproduce, so you are dealing with the last generation. The Knockout will provide another layer of control and prevention. And if you regularly vacuum cracks, crevices, and areas where debris collects, then it can help speed up the eradication process.

Hope this help!