Discouraging Paper Wasp Nests

This question about paper wasp nests was sent to our 'Bugs site:

I deliver propane for a living in NW Washington State and encounter a lot of paper wasps. My policy is live and let live and for the most part I can go about my job in fairly close proximity to even large nests (five inches diameter) and get stung rarely.

Lately I have seen a trend of the nests moving down from the inside of the tank lids to the plumbing, which is logistically not a great place for them to be, and is unfortunately an adequate reason to destroy the nest.

My question then is, do you know of some natural non lethal 'detractant' I could spray on the plumbing parts of the tank to make them non attractive for nesting? Something like cayenne or some herb, something that might give off a smell in the heat or????  The nests are ok in the tank lids - I understand it is a hot/safe place to build them - they just need to stay off the plumbing.

My answer:

The paper wasp you are encountering is actually a fairly new "invader" species in the US called the European paper wasp (click the link for picture of these paper wasps and their nest). These new paper wasps make much larger nests than our native paper wasp species and the wasps are somewhat more aggressive.

There are no sure-fire ways of discouraging nest building but threatening or dangerous nests can be easily managed with new low toxicity, plant oil-based sprays that should not damage the plumbing. These sprays are made from plant oils, not conventional synthetic pesticides. For example Rescue W-H-Y Spray for Wasp, Hornet, and Yellowjacket Nests which is made entirely from natural plant oils.

One final thought: since these wasps only initiate nest building once a year in the spring, any areas that are treated should remain wasp-free for at least a year.