OVIPOSITIONAL PREFERENCE AND DEVELOPMENT OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) IN RELATION TO ALFALFA

A field survey from February to June 1995 in the Imperial Valley, Cali fornia, revealed lower densities of silverleaf whitefly, Bemisia argen tifolii Bellows & Perring, eggs and nymphs on alfalfa than on broccoli , zucchini, cantaloupe, and cotton. To determine if this pattern was c aused by ovipositional preference, studies relating preference to alfa lfa and the other crops were conducted under greenhouse conditions. De velopmental time, survival, and fecundity were also determined. Mean d ensities of adult females per square centimeter of foliage were signif icantly lower on alfalfa than on zucchini and cantaloupe, and mean den sities of eggs and nymphs were significantly lower on alfalfa than on zucchini. Egg hatching rates on different plants did not differ signif icantly. In a greenhouse maintained at 27 +/- 2 degrees C, mean develo pmental time from egg to adult was not significantly different on any host: 22.5 d on alfalfa, 22.2 d on broccoli, 21.7 d on cantaloupe, 21. 3 d on cotton, and 23.0 d on zucchini. Under cooler outdoor temperatur es (11-35 degrees C) and conditions, whiteflies developed significantl y slower from egg to adult on alfalfa (39.4 d) than on cotton (37.4 d) . Percentage of whitefly survival from egg to adult on alfalfa, brocco li, cotton, and zucchini did not differ significantly in the greenhous e study. Under outdoor conditions, the percentage of adults eclosing o n alfalfa (56.3) was significantly less than on cotton (84.3).