At one time or another we have all seen these tiny snowflakes fluttering about a plant. A major infestation of whiteflies can look like a flying fog! They can seem to come out of nowhere and all of a sudden! They are small winged insects which look more like moths than flies and they multiply like crazy!
Whiteflies are not true flies. They are relatives of mealybugs, scales and aphids. Like these sucking insects, whiteflies attack the leaves, buds and stems sucking the juice out of them. Although considered more of a nuisance than anything else, large numbers of whiteflies can really stress plants. The leaves of infected plants may turn yellow,twisted or stunted, and wither and drop prematurely. This insect has a host range of more than 250 ornamental and vegetable plants.
As do their relatives, whiteflies secrete “honeydew” which lures other nuisance insects onto the host plant. Ants, wasps and beetles feed off the honeydew. And when the honeydew goes bad it grows Black Sooty mold. This mold damages the plants preventing them from processing food properly!
Whiteflies cannot overwinter in freezing temperatures outdoors in the north, but can thrive year round in the south and in greenhouses, hence the name of the most prevalent Greenhouse Whitefly! Many plants become infested in greenhouses and transfer the whitefly to other plants in the garden.
Prevention is the best management. Infestations typically originate from infested plant materials. Carefully check all new plants and quarantine them before moving them into a room with susceptible plants.
Insecticidal soaps work well with adult whiteflies. They are safe so you can spray any plant – including fruits and vegetables – without any hazard to people or pets that may be eating the harvest. Soap is certified for organic gardening so it’s an excellent choice for organic growers. These are contact killers for both insect and mite pests. They penetrate the body of the pest and result in rapid death. Keep in mind that white flies in all stages spend virtually all their time on the undersides of leaves. Make sure to cover the hard to reach spots when spraying.
Whiteflies have about a 30 day lifespan. They follow the life cycle of most insects – eggs to crawler to nymph to pupae to adult and they reproduce quickly. About four days from emerging from the pupae adults laying eggs. Insecticides are not effective against immature stages of whiteflies, applications need to be made every four days to kill adults before they begin to lay eggs for the next generation. Up to 7 applications may be needed to bring well-established infestations under control.
There are other insecticides available for whitefly control. Make sure to read the product label for use on crops and directions for preparing spray solutions.