Oscillating Weaponry Against Whiteflies

If you discover your hibiscus or any other plant covered with the new giant whitefly (the one that makes all the white filaments and fuzz), set up an oscillating sprinkler (like a Rainbird) on a spike or stand, and let it blast the bush for an hour or two.

That’s a hot tip from Adrian Wenner, professor of natural history at UC Santa Barbara and coauthor of my favorite bug book, “Tiny Game Hunting” (Bantam, 1991; soon to be republished by the University of California Press).

He came upon the idea of pulsating sprinklers, figuring there had to be an even more effective way than the universally recommended cure of blasting pests off with water. After setting up the oscillating sprinkler and letting it blast the bush for an hour or so, he came back to find all the whiteflies on the ground. Even the winged adults. “They flew away,” he said, “but tended to come back and then get blasted again. The ground was covered with whiteflies and their webs, like it had snowed. The pulsating action seems to do the trick!”

To make sure, he sprays the grounded whiteflies with soapy water, so they never rise again.

Although blasting with plain water is the recommended control, another trick (for those not using Wenner’s sprinkler method) is to add paraffin oil (like Pest Fighter or SunSpray Ultra-Fine) to the water.

This year-round oil coats and smothers the whiteflies. Use 4 tablespoons per gallon, and blast bushes with a hose-end sprayer. You’ll most likely need to spray three or four times each summer.

Stay away from poisonous chemical controls because they also kill natural predators, making the whitefly population explode. Whiteflies can lay 10 times as many eggs as their predators, so you don’t want to give them an edge.