White flies

I have a very bad white fly infestation. I’ve been using oil spray. It helped for a little while, but then they came back. Now they are worse than ever. My leaves are slimy and brown. I feel for my plant. What’s the solution?
Major Tom,
Bloomington, California

White flies are 1/16 of an inch long and totally white. When a plant is disturbed, they flutter around and then settle back down. White flies are a serious pest of cannabis that suck on the juices in the leaves, which weakens the plant. In addition, they serve as a vector for diseases. When they suck the juices they can transfer bacteria and other diseases between the plants.

There are several ways to eliminate them. Pyrethrum sprays and fogs are effective in knocking down the population. However, a single spray or application will not eliminate the pests. This minimizes the immediate damage, but their children, hatching from eggs laid on the underside of the leaves, will soon emerge. Spraying every other day four times may eliminate them, but it is more likely to leave a few hardy individuals who are pyrethrum resistant. These will start reproducing. However, if there is not much time before harvest, they can be tolerated.

Botanigard and Naturalis-O are products that contain the living fungus beauveria bassiana. This fungus attacks insects, causing their death. It is very effective against white flies. Several applications are needed to catch the insects as they emerge from their juvenile form.

Another possible solution is to get some Encarsia Formosa ? a non-social wasp so tiny that once you release them you may never see them again. They lay their eggs in the white fly larvae. The developing wasp kills the larvae as it receives nourishment from it. These wasps are very effective at their job.

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