Sprayed all the post around the pool with WD40

[Bonzo]

It deters Yellow Jackets from building nests! Walking around spraying every little hole with the stuff. Hey a spray can of prevention....

[DIGGER]

I USE WD40 ON THE GARBAGE TOO.  SPRAY A LIGHT SPRAY OVER THE GARBAGE WHEN YOU PUT THE BAGS IN THE GARBAGE CAN AND YOU WILL NOT HAVE A FLY AND MAGGOT PROBLEM IN THE GARBAGE

[PAVALKER]

Wooden posts?     Might deter Wood Boring Bees... but I think Yellow Jackets are ground or bush/shrub  inhabitants are they not?

[designer]

we have the paper nest type that build a next anywhere they can hang a next.  I like the old aerosol can with lighter trick when I find a nest.

[Valker]

we have the paper nest type that build a next anywhere they can hang a next.  I like the old aerosol can with lighter trick when I find a nest.

If you follow your application of lots of WD40 by checking to see if you used enough (you can easily see that if you use a lit match to check), they will not rebuild.