The number of sprays required to control whiteflies (Bemisia tabaci [strain B] = B. argentifolii Bellows &Perring) in Arizona has dramatically declined in the last two years. In 1995, Arizona averaged 6.6 sprays against whiteflies, but this declined to 1.99 and 1.81 sprays in 1996 and 1997, respectively (Williams, 1996, 1997, 1998). This dramatic reduction was coincident with the introduction of the insect growth regulators (IGRs), Knack^® (pyriproxyfen) and Applaud^® (buprofezin), to Arizona through Section 18 exemptions.