I almost hate to suggest the following, for I am sure I will be blasted. It may also not be appropriate for your location.
If you can pour something into the hole, a small amount of gasoline will get rid of the hornets. I do not think it kills them so much as the smell drives them out. In my case I had a hole in the back yard and used a funnel and a couple ounces of gas.
There is a foaming hornet spray. I shoots from a distance and then expands into foam. Do is at night when they are in and shoot it into the entrance hole.
And here's how to disperse it:
Wait until night, then duct tape all the cracks except one small hole. Stick the nozzle of a spray can of insecticide in the small hole, start spraying, and beat on the steps. If they can't get out the spray will get them all. Red
I've had a similar situation several times. Wasps nest in the crosstie retaining walls all around my home. Vicious little bastards.
I use an insect fogger, taped to a long pipe or conduit. turn it on, then hold it up to the access hole until it stops. You may be able to rest it against - or on - something so you can back off further. It works for me.
As others have said, at night, or the coolest time of day is best.
Another thing I've done that is satisfying though less effective: Get your electric leaf vaccum, the one with the 4-ft long by 4" diameter suction nozzle. Connect and extension cord, turn the switch on to high, but don't plug it in. Prop the sucking end up so it's at their entrance hole. then walk back and plug the unit in. As the critters try to enter or leave, they get sucked in and mulched. I had a large conical pile of yellow wasp pieces after 30 minutes or so. All it does is reduce the population though.
Sounds like a really, really bad idea. Not knowing structure or air-flow, it allows for collection of vapor and possible fire. There are good products, intended for the job and safe to use.
It's time to consider paying a pro to do the job.
On Thu, 25 Jun 2009 07:37:52 -0500, against all advice, something compelled Ken , to say:
Ammonia and chlorine bleach make chlorine gas.
Just sayin' . . .
Hornet spray killer does the job.
They won't if you wait after sundown, they don't fly in the dark. The hornet spray kills on contact.
Sevin dust doesnt make them angry at all. I have dusted it directly on them.
Jimme
Seal up the whole stairway airtight with plastic sheeting. Now get about 5 or 6 aerosol "bug bomb" cans and gas them to death under the plastic by releasing the bug bombs under the sealed plastic. Leave the plastic in place for a few days so they are entrapped within the poison. Nothing will live through that. Make sure the plastic entirely seals the stairs by duct taping it to the house and slab, etc. Additionally you can pump hornet liguid with an atomizer (a paint sprayer) under the plastic, they gotta breath and eat all that poison some time.
Be sure to get a good spray. There are some cheaper brands on the market that don't knock them down for 5-10 seconds, and that is plenty of time for them to nail you. Spectracide Pro will drop them instantly. Spectracide makes a cheaper spray that takes about five seconds to bring them down. When you have 100 mad yellow jackets coming at you, that will be the longest five seconds of your life!
Use clear plastic that lets in light so they have a desire to exit their nest into the poison vapors.
Caulk all the cracks or use Great Stuff foam.
With the canned wasp spray, I've sprayed a lot of nests and never had this happen. The spray knocks them down and loose ones ignore me. Same for an aqueous stream out of a tank sprayer. Perhaps they think it is raining since they ignore me there too.
And next spring, he'll be rebuilding the steps because the wood rotted out. Such structures are made to breathe for a reason.
I'd just douse it every other evening, for a week or so, with one of the squirtgun spray cans from raid or whoever. If the holes are small, they don't fly in and out, they walk. Douse the entry points, and they will pick up enough of it.
They also sell powder stuff, at Farm Bureau. I used it a couple years ago for a ground bee infestation. (Got tired of wearing long pants to mow, in 90 degree weather.) I presume there is something for hornets available. Just a few puffs every night at the entry points.
If the steps are starting to show their age, I'd look at precast concrete ones to replace. They don't all scream 'trailer park' any more- some are actually pretty decent looking.
-- aem sends...
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