I have some bird houses just for decoration/door stop ect on my porch. The birds don't use them of course, but red wasps I am having trouble with. I have rocks in them to keep them from blowing over when it storms and to be heavy enough to hold the storm door open. I'm wondering about dropping a moth ball in there? Would that keep the wasps out? Any other ideas?

I apologize, I can't suggest an alternative, but definitely not mothballs
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I would put a plug in the door perhaps a wine cork to keep the insects out.

I agree with both no mothballs, and plugging the opening to the birdhouse. Wasps love sheltered enclosures for building their nests.

the hole is about 2 inches across, rather large, I wonder about gluing a jar lid over it? maybe that would work?

Sure, why not? Sounds like an excellent solution to me

If you read about moth balls, I don't think you would want them anywhere on your property.