MONITORING FOR ORGANOPHOSPHATE-RESISTANT AND CARBAMATE-RESISTANT ARMORED SCALE (HOMOPTERA, DIASPIDIDAE) IN SAN-JOAQUIN VALLEY CITRUS

Citrus fruits infested with California red scale, Aonidiella aurantii (Maskell), and yellow scale, A. citrina (Coquillett), were collected f rom a total of 68 orchards in four counties in the San Joaquin Valley of California over three seasons to test for insecticide resistance. C alifornia red scale populations were collected from Madera, Fresno, Tu lare, and Kern counties. Yellow scale populations were fewer in number and were found only in Tulare County. The results of laboratory bioas says of the infested fruit suggest that resistances to the organophosp hate insecticides chlorpyrifos and methidathion are developing in the two armored scale species in this region. Armored scale resistance to the carbamate insecticide, carbaryl, appears to be less intense than f or the organophosphates at this time. The populations showing the lowe st percentage of mortality to any of the tested insecticides were loca ted in eastern Tulare and Kern counties. An insecticide resistance man agement strategy for this citrus growing region is discussed.