The sweetpotato whitefly, Bemisia tabaci MEAM1 Gennadius, is a pest of many economically important crops globally and causes significant losses in Florida vegetable production. In 2020/21, a serial dilution bioassay was administered to field populations of B. tabaci MEAM1 collected from various vegetable and weed hosts across south Florida to monitor insecticide resistance. The insecticides evaluated were afidopyropen, cyantraniliprole, dinotefuran and flupyradifurone, which target whitefly adults, and spirotetramat, which targets whitefly immature stages. The serial dilution bioassay exposes individuals to a range of active ingredient concentrations on cotton leaves treated by a leaf-dip method. The concentrations of active ingredient required to kill 50% (LC50s) were calculated by probit analysis using POLO PC, LeOra Software. A susceptible laboratory colony of B. tabaci MEAM1 and a colony of B. tabaci MED were also tested. Overall, populations demonstrated susceptibility to most active ingredients evaluated, however tolerance to spirotetramat appears to be an emerging problem among field populations of B. tabaci MEAM1 in Florida. The reference laboratory colony of B. tabaci MEAM1 remained the most susceptible for all the products and the B. tabaci MED colony among the least susceptible for most of the products assessed.
