Why Sample Nymphs?
Sampling is necessary for timing control of whiteflies. Sampling nymphs is particularly important to gain the most benefit from the application of insect growth regulators (IGRs). Unlike most of the insecticides used against whiteflies in Arizona in the past, IGRs affect immature whiteflies instead of adults. Timing the first use of an IGR requires sampling both whitefly nymphs and adults. The objective is to time the first use of an IGR during the first period of accelerated population growth. IGRs should not be used late in the whitefly infestation. Therefore, IGRs will probably be among the first insecticides used. Adult sampling is sufficient for timing use of insecticides other than IGRs. Use of IGRs within an integrated resistance management program is explained in IPM Series No. 3 & 4.
