How does the IGR work?

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QuestionsCategory: Flea InfestationsHow does the IGR work?
Kkelly asked 2 months ago

I moved into an apartment that had fleas. There shouldn’t have been that many because they put in new carpet the day I moved in. However, I retreated my dog within a couple of days after I realized the problem. I had to wait a week for pest control to come and the first time he did not use an IGR. The 2nd time I demanded it so he sprayed Pivot  Ultra. I vacuumed everyday after he sprayed the first time and every other day since the 2nd time. Shouldn’t the IGR keep the eggs from hatching and the larvae stage from pupating? I know the pupae stage is not going to be affected by the spray but what about the others?
Thanks for your help and for this awesome site

Kkelly replied 2 months ago

Also Adam, how often do I need this guy to come back and spray with the IGR? I an still vacuuming up live fleas?

1 Answers
Adam Retzer Staff answered 2 months ago


Yes, the IGR will prevent eggs and larvae from reaching adulthood. The problem is that sprays can’t penetrate to the depth of carpets where the fleas develop. Many of the fleas there won’t be affected. So, while the IGR will prevent new eggs that fall onto the carpets from developing, some of the fleas already developing at the base of the carpeting will survive and emerge as adults. These are likely the fleas you are seeing emerge.

You shouldn’t need another treatment. The IGR will remain active for 7 months. Just continue the regular vacuuming. Here’s a page on how often to vacuum and the reasoning behind it. It often takes around 8 weeks for infestations to completely end. The last generation of fleas in the environment need to mature, emerge, and then die.

Warm regards,

Kkelly replied 2 months ago

So what about the adults when they finally emerge from the pupae stage? Will the IGR keep them from laying eggs? Also if the larvae eat eggs that have the IGR on them will it keep them from moving on to the pupae stage?

Adam Retzer Staff replied 2 months ago

When the adults emerge, they will seek a host. Upon jumping on the treated dog they will die. Or they will get sucked up by the vacuum and die. Or they will die from starvation.

Yes, the IGR in the environment and on the dog will sterilize the females, so no new eggs can be laid.

If larvae consume IGR exposed eggs then they shouldn’t be able to develop. There wasn’t a specific study done on this, but there was one done showing that larvae can’t develop if they consume ‘flea dirt’ from IGR exposed adults.