Recently, the infestation levels of the sweet potato whitefly, Bemisia tabaci, have increased substantially on a number of crops in large areas of the southern U.S. Unfortunately, this insect has a well documented history of insecticide resistance development. Therefore, it is important that resistance management strategies be implemented if the effectiveness of current insecticides is to be preserved.

One of the more important factors in a resistance management program is a simple, robust, reliable test which can be used to monitor changes in insect susceptibility. Data from the test can be used to measure the effectiveness of the resistance management plan being used and to guide the selection of insecticides to control the pest. The whitefly vial test (WVT) is such a test. In this test adult whitefly are exposed to residues of contact insecticide (bifenthrin and endosulfan) for three hours in a glass container after which mortality (or survival) is determined. This test can be used to rapidly determine whitefly susceptibility in a number of locations over a relatively large area, populations in a glasshouse, or to monitor susceptibility changes of a whitefly strain through a season.