Adults are less than 1/8” long and, like their name suggests, have white wings with pale yellow bodies. Adult whiteflies congregate above and under leaf surfaces, and disperse in clouds when disturbed.
Greenhouse whiteflies develop in 30-34 days; silverleaf whiteflies develop in 35-39 days. Both species develop according to the following life cycle stages:
-Egg (hatch in about 8-11 days)
-Crawler (lasts about 7 days)
-Nymph (three instars - about 10 days)
-Pupa (doesn’t feed)
Prevent whiteflies from entering growing areas with screens over intake vents and by keeping doorways closed. Keep unused growing areas empty when possible between crops. Remove plants around the perimeter of the greenhouse that may harbor pests. Dispose of infested plants and plant debris in sealed plastic bags to prevent reinfestation. Avoid overfertilization.
Pesticides can be used to control whiteflies but be sure to keep in mind:
1) Foliar pesticides are effective when there are mostly crawlers, nymphs, or adults present (soil systemics may provide better control) 2) Plant surfaces, including the undersides of leaves, need to be covered for foliar applications to be effective 3) Prevent insecticide resistance by avoiding consecutive treatments using the same chemical class. Yellow sticky traps, cinnamon oil, insecticidal soap and capsaicin are all suggested remedies for white fly infestations.
Both greenhouse and silverleaf whiteflies have natural enemies that are available for commercial use, such as the black ladybeetle. The use of biological control agents has been effective for suppressing whitefly populations in indoor plantscapes and in greenhouses as a part of an IPM program. As a general rule, making several small releases over a period of time rather than one single massive release is recommended for best results. If pesticides are used, waiting a minimum of two weeks and/or two waterings before releasing biological control agents is advised.