UC Master Gardener Julie Taylor said on Mar. 26 that the small clouds of white flying insects seen around citrus, tomato, crepe myrtle, roses, and squash are likely whiteflies. These insects can appear as mature flies or as tiny nymphs on the underside of leaves and may leave behind deposits of white wax, sticky honeydew, or black sooty mold.
Whiteflies are related to aphids and mealybugs and tend to develop rapidly in warm weather. While low populations are usually not harmful but unsightly, large infestations can cause leaves to yellow or fall off and may lead to significant damage in vegetable crops such as sweet potatoes.
Taylor said prevention is key: “Whiteflies like dry, dusty conditions, so hosing down known host plants throughout the dry season can help keep populations low.” She also recommended using yellow sticky traps for monitoring and removing infested leaves. Controlling ant populations is important because ants protect whiteflies from their natural predators while feeding on honeydew.
If insecticides are used, Taylor advised choosing insecticidal soap or neem oil rather than systemic insecticides due to their potential impact on beneficial insects and pollinators. “Whiteflies do have natural enemies. General predators include lacewings, big-eyed bugs and minute pirate bugs,” she said.
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