Conserving beneficials, planting smooth leaf varieties, and avoiding late planting are also a means of reducing the likelihood of whitefly problems. However, when and if the problem develops, control of silverleaf whitefly with insecticides is expensive and difficult. 1999 demonstrated to us that silverleaf whiteflies can significantly reduce yields. This pest is unpredictable, but failure to control damaging infestations can be very costly. However, multiple applications will be needed since we will probably have continued migration and emergence of whiteflies in severely infested areas.
Control is difficult.
A starting point for a threshold would be 5-10 adults per leaf. To scout silverleaf whiteflies, gently turn leaves and count the number of whiteflies on the underside. Knack is the most consistent treatment for management of silverleaf whiteflies. It is also the most expensive. When females feed on foliage treated with Knack, her eggs will be sterile.