ACTION THRESHOLDS FOR BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) IN CANTALOUPE

A range of action thresholds for the control of silverleaf whitefly, B emisia argentifolii Bellows & Perring [previously b-strain sweetpotato whitefly, Bemisia tabaci (Gennadius)] was evaluated in 2 field experi ments, one at Weslaco, TX, with a low population density of B. argenti folii and one at Yuma, AZ, with a high population density. In Texas, a ction thresholds for whiteflies of 0.5, 1, and 2 large nymphs per 7.6 cm(2) of leaf area and of 1, 3, and 6 adults per leaf were tested. In Arizona, action thresholds of 3 and 10 adults per leaf were tested. Al l thresholds were compared with weekly insecticide treatments and an u ntreated control. The threshold treatment in Texas that resulted in th e highest net return (70% increase over the untreated control) was 0.5 large nymphs per 7.6 cm(2) of leaf area. The threshold treatment in A rizona that resulted in the highest net return (170% increase over the untreated control) was 3 adults per leaf. Both of these thresholds re sulted in 6 applications of insecticide or approximate to 1/2 of that used in the calendar treatments.