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This is the third in a series of three articles discussing whiteflies in the California home garden.
Steps to control active whitefly infestations:
1) For early and small infestations, use a strong stream of water, as from a hose nozzle, to clean the undersides of leaves. This may require careful attention, such as spraying the undersides of leaves one at a time, and becomes untenable for large infestations. If you catch a new infestation that includes only a few leaves, the leaves may be removed and destroyed.
2) Use a cloth or paper towel with rubbing alcohol, or a mixture of 1 teaspoon of biodegradable soap plus 1 tablespoon of tea-tree oil or lemon juice per quart of water to clean the undersides of infested leaves by hand. The tiny, flat nymphs must be eliminated to stop infestation.
3) Ants protect whiteflies by fighting off predatory insects in order to harvest honeydew. Eliminate ant nests using boric-acid or borax ant bait, or apply sticky barriers to the trunks of trees and woody plants. When using sticky barriers, be sure to eliminate all other avenues for ant entry, such as by pruning branches that touch the ground or nearby structures.
4) If the above methods don’t stop infestation, consider removing and destroying infested leaves. Removing too many leaves may harm the infested plant or tree.
5) Insecticidal soaps and oils are difficult to use effectively, may require repeat applications, and may harm plants, but can be considered as a last resort. Pesticides often do more harm than good, leading to repeat cycles of infestation, as they kill natural enemies, which recover more slowly than whiteflies. Careful monitoring with a combination of the four steps above is best for most home-garden infestations.
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