Encourage buildup of beneficial insects by avoiding the use of nonselective pesticides and by protecting their habitat. Host free periods are valuable for controlling several of the whitefly species. Contact your Cooperative Extension Office for a list of hosts that harbor the silverleaf whitefly. However, when dense populations of adult silverleaf whitefly are migrating, monitor seedling carrot fields at least twice weekly and treat if necessary. Occasionally dense colonies of silverleaf whitefly nymphs can necessitate treatment of bunching carrots to prevent honeydew and sooty molds from severely contaminating the carrot tops.
Whiteflies can be very difficult or almost impossible to control with insecticides.
Natural or introduced biological methods provide the best long-term solution to keeping whitefly numbers at a minimum along with reducing host plants in areas of heavy infestation. If you treat for silverleaf whitefly, make applications before pests build up and contaminate carrot tops with honeydew. Rotate pyrethroid treatments with a treatment of insecticidal soap to help slow development of insecticide resistance. There is some evidence of endosulfan resistance in populations of silverleaf whitefly in the Imperial Valley. Emergency registrations may be in effect in some areas for new materials.