Summary:
Removing a wasp once the wasps have died should be done as soon as possible. The leftover nest may contain dead insects or stored food that will decay. Once it begins to decay you will be fighting mold and other invading insects.
Sam S; Vancouver, British Columbia asks: I had a wasp nest inside my living room wall. I heard buzzing in the walls and treated the spot with a spray insecticide. Now, there is a strong, "musty" odor coming from a section of the living room wall exactly where I heard the buzzing. Do wasps nests have an odor or is it possible I now have a mold problem?
Dear Sam: Yes, you could have a mold problem inside the wall. That's why we never suggest treating wall voids with liquid sprays. A professional exterminator attempting a wasp nest removal would or should only use pesticide dusts to treat inside walls.
Remember, the wasp nest, which could have contained hundreds or even thousands of larvae, has had the attending adults killed. The larvae have died and are rotting inside the wall and are probably the cause of what you are smelling.
It didn't help matters when you introduced liquid pesticide into the walls.

Yellow Jacket nest
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The space inside walls are supposed to remain dry. The liquid sits there creating a wet environment and suddenly the development of mold becomes a real possibility.
We always recommend opening a wall to remove the nest after the wasps or bees have been eliminated. Now you can kill two birds with one stone. Open the wall to remove the dead nest and remove any materials that have mold caused by the moisture you injected.
Comments
Barbra
24 Jun 2010, 09:27
We have a wasp nest inside the dryer vent. They are flying in and out of
the vent of the exterior wall above our deck. Any ideas how to kill and get
rid of the nest? I can hear them inside the house in the wall, but I'm
unsure how to reach them since they are in the pipe that leads to the
laundry room.
Thanks for any suggestions.
Ask the Exterminator
24 Jun 2010, 10:55
Do not ask your questions in this box. Post at top of page.
Cheryl
14 Jul 2010, 12:49
I have bee/wasp (not sure which) that has made a dirt nest in the screw
hole of my lawn furniture. Small worm like critters fall from these holes
(this may be their larva). They also may a dirt nest in a wood wind chime I
have on my porch. Can you tell me what kind of insect I am dealing with and
how to get rid of them. The insect is about 3/4 in long, is brownish black
with some yellow stripe,and looks to be a bee.
Ask the Exterminator
14 Jul 2010, 13:53
I can't ID without a picture and you can only send me a picture if you use
the "Ask a Question" button at the top of this page.
Sim
23 Sep 2010, 00:00
I had a wasp nest inside my siding outside by my familyroom window. I
called a pest control company( terminex) that came and killed the nest. The
wasps have been gone for nearly 3 weeks and now I have a dead animal smell
in my family room near the window that the nest was. Will the smell go away
by itself. Who can come and remove the nest for me..Does the pest control
company do that? My husband is not at all handy and wont go near the
project so we will have to call in someone. The nest is outside my house in
the siding. Please help!
Ask the Exterminator
23 Sep 2010, 09:20
The pest control company is not responsible for removing the nest unless
you specifically contracted for that service. Most times it's the homeowner
who is responsible. The nest is usually removed by opening an inside wall.
That means new wall board and painting. You'll need a contractor who does
that type of work.
Gina L
30 Sep 2010, 21:56
We have a wasp infestation. They are literally crawling all over our house.
We have a stucco home with tile roof. Is it possible to have them inside
our walls? They keep finding their way into one of our rooms by the dozen
on some days. We cannot figure out how they are getting in. I am ready to
move to a new house. Pest service is here every day treating our house. Our
attic has been fogged. Sometimes I think I hear them inside the walls, not
buzzing but like they are running into the walls. How can we possibly
locate them. I can send you a video of what they do on the outside of our
house. They bunch up in about a 12" circle and just crawl all over each
other. Will they die in the winter?
Please help us, we have two small children.
Ask the Exterminator
30 Sep 2010, 22:24
The wasps will die with cold weather, but fertilized females will leave the
nest beforehand and find a place to overwinter. You need to observe their
activity from the outside at sunset. You'll see them returning to their
nest. Once you locate that entrance hole it should be treated with a
pesticidee dust. The entrance hole should be left open until all activity
has stopped.
L K Brown
29 Nov 2010, 13:54
Can I do that now in Nov? Does the fertilized female come back in warm
weather?
Can I just have the last row of siding rreplaced. It has pulled away and
providesa slim opening. The siding guy said I ccould do that.
But do they return again?
If I use the powder at the opening how far up does it spray? I can't see
inside there. What is the name of the powder spray?
Thanks.
Ask the Exterminator
30 Nov 2010, 11:11
The fertilized female does not often return to the exact place where the
previous nest was located. You need to watch for wasp activity on the
outside of the house in the spring. If you see the hole or location where
they are emerging, that general area can be treated with the dust. The dust
need only coat the entryway. It does not need to reach the nest.