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Pest Control/Wasps in Basement

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QUESTION: Hi There,

Over the past month, we noticed many wasps coming & going from a certain spot on our front porch. My brother in law followed them under the porch, and determined that they were coming from a crack in the foundation. He decided to try and treat it himself, which seemed to work outside, however now we are constantly finding both dead & alive wasps in our basement. There's never more than 10 at a time, but we are not having any luck to figure out where they are coming from. I'm not sure what to do next. Should I be calling a pro in to take a look? Thanks!

ANSWER: Allison,

If the initial treatment included sealing the nest's entrance hole that would explain why the wasps have entered the basement - never seal the entrance to a wasp nest associated with a building because it will only drive them inside. Locating the new entrance (now into your basement) may be very difficult and I doubt that a PCO would have any more luck than you would. Your best option might be to re-open the original entrance (carefully!) and treat the nest with a "wasp&hornet" type spray (see http://www.livingwithbugs.com/yel_nest.html).

Jack DeAngelis


---------- FOLLOW-UP ----------

QUESTION: Hi Jack,

Thank you for your help! My brother in law did not seal the outside entrance. He sprayed into the crack with Raid Wasp & hornet. So I'm not sure why they are no longer going outside? Do you think we should try spraying again to kill whatever remain?

Answer
I suspect the actual nest may be some distance from the treated foundation crack so that the insecticide never contacted the nest. The wasps may be avoiding this entrance now because they can detect the insecticide around this opening. However, since you are finding some dead wasps it is possible that the nest is dying or at least has been disturbed. You might wait a week or so and see if the numbers go down. Otherwise you could try re-treating the original opening and try to get the spray deeper into the wall.

Jack DeAngelis  

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Jack DeAngelis

Expertise

I can answer questions about the control of pest insects, spiders, mites and related arthropods. These household pests include termites, carpenter ants, powderpost beetles, nuisance ants, bed bugs, cockroaches, fleas, wasps, and many others. I can also answer questions about using pesticides and other pest control tools such as baits and traps.

Experience

I am a retired university extension entomologist. I've taught and conducted research in urban and agricultural entomology. I've published over 70 extension publications, 20 research publications and several books about insects.

Education/Credentials
Ph.D. in Entomology

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