RESISTANCE MONITORING OF THE SWEET-POTATO WHITEFLY (HOMOPTERA, ALEYRODIDAE) IN THE IMPERIAL-VALLEY OF CALIFORNIA

A resistance monitoring technique using yellow sticky cards sprayed with insecticides efficiently and sensitively detected resistance in field populations. The distribution of resistance in the sweetpotato whitefly, Bemisia tabaci (Gennadius), in Imperial Valley, Calif., was determined with this technique. Thirty-two populations exhibited various levels of resistance to sulprofos (resistance ratio [RR] ranging from 19 to 104) and cypermethrin (RR ranging from 14 to 82) during 1987 and 1988, indicating that insecticide resistance is widespread in the Imperial Valley. The advantages of this new method for monitoring resistance in whiteflies are discussed in relation to conventional leaf bioassays.