ASK THE EXPERTS: Hornets on a PV Array

Wasp nest
Wasps like to make their nests in shaded, secluded spaces like those found on the back of PV modules.
Wasp nest

I have a client who has developed quite a problem with wasps nesting behind her solar-electric array. Does anyone have experience getting rid of them? I’m afraid of the possibility of insecticide sprays or detergents damaging the modules’ back-sheets. Is that a legitimate concern?

Dana Brandt • Ecotech Energy Systems

While I’ve heard it recommended, I’d be wary of using dish or laundry detergents on PV modules because they can contain petroleum surfactants that may damage the back-sheet. (That’s why the agents are so effective at stripping oil off bird feathers after an oil spill.) Safer brand insecticidal soap, which uses potassium salts of fatty acids, will kill wasps, and is nontoxic and petroleum-free.

I deal with wasps nesting on my ground-mounted system with a high-pressure sprayer on a garden hose. I have to go out there a few times in the spring to knock down the nests, but the wasps eventually get the idea that they aren’t wanted. Two years ago, I had a nest of white-faced hornets build one of their marvelous cone-shaped nests on the back of the array, and it was pretty large by the time I saw it, so I left them alone. I like hornets because they kill and eat yellow jackets. Unlike yellow jackets, if you don’t bother the hornets, they won’t bother you.

For outdoor-mounted solar-electric equipment, such as inverters and other outdoor equipment enclosures, make sure that you seal or screen any openings that could be potential entryways for insects, birds, or rodents. You still need to ensure that the equipment has proper ventilation, but prevention can sometimes be a great cure.

Brian Teitelbaum • AEE Solar

Comments (1)'s picture

According to the book 'Natural Solutions to Things That Bug You' by Dr. Myles H. Bader, Use a CO2 fire extinguisher at night for best results. They are agitated by bright light, so use a flashlight with a red filter. Place some soda pop in a tall plastic soda bottle and leave it out. The wasps will go in, get confused, and not find their way out. You should hang the bottle at night. When the wasps are gone, cap the bottle and dispose of it.

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