This sounds like a real can of worms---er, wasps!

I'm not sure I understand what "subdivision" means, and if the same builder built the houses and the common fence, or if YOU paid for the fence, and it is on your property, or on the property line.

Are you on speaking terms with your next door neighbor??? It sounds like he did a small-minded thing (even illegal) by installing boards on YOUR fence without even asking permission, and apparently didn't get your agreement beforehand----and now there's a wasp problem, which is clearly of HIS DOING-----he sounds like a real jerk!

I think you'll be able to get rid of the wasps eventually, either by waiting for cooler weather, or attacking them at night with wasp spray when they go into a torpor (lassitude); I'm less optimistic that your relationship with the neighbor will survive-----it's best just to stay away from people like that, unless he's willing to make amends on this deal.