Whiteflies cause yellowing, mottling, and wilting foliage.
Whiteflies are small insects whose bodies and wings are covered with a white powdery wax as adults. They can be found on the undersides of leaves, and, when disturbed, will fly around the plant and eventually return to feed. The nymphs (immature stage) will attach themselves to the undersides of leaves and don’t move.
Damage Caused by Whitefly
Whiteflies will feed on numerous indoor plants as well as several annuals, perennials, and vegetables. They have piercing-sucking mouthparts and feed on plant juices. Feeding can cause yellowing, mottling, and wilting foliage. In severe cases, plant death may occur. They tend to feed mostly on the lower side of the leaves.
Life Cycle of the Whitefly
Whitefly species that are damaging to cultivated plants are not cold hardy in Illinois. To survive our winter, they must be on plants indoors (house plants, herbs and greenhouse crops). The insects (usually in the egg stage when they are difficult to see) are often shipped north on flower and vegetable transplants grown in the south.
- Female whiteflies lay eggs on the lower leaf surfaces of plants.
- Eggs hatch 7-10 days after being laid.
- The first instars are mobile and resemble scale insects. They will search for a suitable place to feed and remain there before emerging as adults.
- There can be several generations per year.
Management of Whiteflies
- On indoor plants one can try using yellow sticky traps to capture the adults. These work much better if the foliage is disturbed daily, causing the whiteflies to fly off of the plant.
- Infestations can also be reduced by discarding heavily infested plants.
- Outdoors, use suggested insecticides according to all label directions and precautions. Insecticidal soap, summer oil, and chemical insecticides are effective.
- On vegetables, be sure to follow the recommended time interval between treating the plants and harvesting the crop. If there is no pre-harvest interval, do not use that insecticide on the food crop.
Contact your county Extension office for current pesticide controls.