Toxicity and growth-suppression exerted by diafenthiuron in the sweetpotato whitefly,Bemisia tabaci

Diafenthiuron (CGA 106 ’630), a thiourea, was sprayed prior to a 48-h infestation by adult females of the sweetpotato whiteflyBemisia tabaci Gennadius, on cotton seedlings under greenhouse conditions; it subsequently suppressed strongly progeny formation of the whitefly, resulting in approximately 50% progeny formation relative to control at 5 mg a.i./l. When the different development stages were separately sprayed directly, the larval stage was the most susceptible, resulting in 50% and 90% mortality of 2nd instars at concentrations of 6.5 and 49.2 mg a.i./l, whereas the LC50 values of adults and pupae were 23 and 45 mg a.i./l, respectively. A mild (30–35%) reduction of egg hatch was obtained at a range of 5–125 mg a.i./l. Thus the potency of diafenthiuron against various stages was in the order larvae > adults > pupae > eggs. Diafenthiuron exhibited a low vapor phase toxicity and had no translaminar effect when tested on first instars ofB. tabaci. The high potency of diafenthiuron against whiteflies described herein, against aphids and mites, as stated in the literature, and against some lepidopterous pests, render this compound an important insect control agent for pests of cotton and other crops.