[Alram]

I had a bunch of wasps building two nests in an empty top bar hive I have. My husband grabbed some wasp spray and sprayed the nests on the inside of the box. Will I ever be able to safely put bees in this box again? How long does it take the poison to dissipate? Is there something to rub the wood with that will help neutralize the poison?

 

[Boondocks]

It really depends on the brand of wasp spray and the active ingredients.
Black Flag Wasp spray has two active ingredients;
Cypermethrin- It is easily degraded on soil and plants but can be effective for weeks when applied to indoor inert surfaces. Exposure to sunlight, water and oxygen will accelerate its decomposition. Cypermethrin is highly toxic to fish, bees and aquatic insects, according to the National Pesticides Telecommunications Network (NPTN).
Prallethrin-Long lasting toxin No degradation time that I found.

You could wash the area with soap and water, rinse thoroughly, and leave exposed to sunlight for several months. Or you could burn it and never have to worry about it again.
.

 

[myrdale]

I'd hit all surfaces with a water hose really good, and then leave it open to air out for a couple of days.

When you say empty, I am assuming that means no comb either.

 

[Akademee]

A lot of these things break down in the UV of the sun, was with soap and water very thoroughly and let it sit out in the sun until next year.

 

[Jack Grimshaw]

Heat breaks down most chemicals.I would toast the affected area with a propane torch.No need to char the area,just a toasty brown

 

[Honeyeater]

Some of the insecticides available here in Australia are made for outdoor use and claim to last several months exposed to the weather. Don’t assume anything.

Having said that I think a propane torch as Jack describes above, and a thorough sand is your best bet. And make your husband do it of course.