Pest Control Library: Whiteflies

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By National Gardening Association Editors

This pest is found throughout the United States. The tiny insects feed in large numbers by sucking plant juices from the leaves and stems of many plants, including tomatoes, cucumbers, lettuce, flowers, trees, and shrubs.

In cold-winter climates, whiteflies are mostly greenhouse or indoor pests, but they can be found in the garden. In mild-winter climates with no winter cold to kill them, whiteflies are serious outdoor pests. In recent years in the Southwest, pests such as the silverleaf whitefly have been among the most damaging to agriculture.

Adult whiteflies hide and feed on the undersides of leaves. They are most noticeable when you rustle the leaves and a cloud of tiny white specks emerges into the air like "plant dandruff," as some gardeners aptly describe them.

Like aphids, whiteflies reproduce quickly, laying white eggs that hatch into white crawlers on the undersides of leaves. Whiteflies thrive in sunny, warm conditions. The crawlers and adult flies suck plant juices, weakening the plants.

Whiteflies secrete a sticky, sugary substance called honeydew that may cause the growth of a sooty black fungus on leaves. Eggs laid on leaf undersides hatch into tiny larvae that look like flat, oval, semitransparent scales. The larvae reach adulthood within a about a month of hatching.

Controlling Whiteflies

Spray plants with a stream of water from a garden hose to dislodge the majority of the pests before applying insecticidal soap or other approved product. For effective control, follow instructions on the product label for an appropriate spray schedule.

To control small populations of whiteflies on houseplants, approach them in early morning and evening when they are most sluggish. Use a vacuum cleaner set on low suction to remove the whiteflies.

Whiteflies cannot survive freezing temperatures. They are reintroduced to northern regions each year on the wind and infested plants. Check plants carefully for whiteflies before purchasing.

Photography by Jeffrey W. Lotz, Florida Department of Agriculture and Consumer Services,

This article is a part of our Pest Control Library.
This article is a part of our Pest Control Library.
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