Vapor toxicity and concentration-dependent persistence of buprofezin applied to cotton foliage for controlling the sweetpotato whitefly (Homoptera: Aleyrodidae).

The biological and chemical persistence of buprofezin above and within cotton leaves, along with its vapor activity and translaminar effect against Bemtsia tabaci (Gennadius) larvae, were studied. The 50% loss of foliar buprofezin varied from a short period (2.3 d) at 62.5 mg (AI)/liter to a relatively long period (13 d) at 250 mg (AI)/liter. At 250 mg (AI)/liter, complete suppression of progeny formation was observed up to 14 dafter treatment; potency was reduced to 50% of its original value in 26 d for suppression of egg hatch and in 28 d for cumulative larval mortality. At least 60-70% of the bu profezin was a surface residue and was responsible for the variable persistence and for a pronounced vapor phase activity. Buprofezin vapors emitted from leaves treated with 450 mg (AI)/liter resulted in 95.7 and 62.4% kill of first instars at a distance of 2 and 4 em, respectively. Less than 4% of the initial deposit that penetrated into the leaves was sufficient to produce a moderate translaminar effect. Treatment of the upper leaf surface with 150 and 450 mg (AI)/liter induced ≈25% mortality of larvae placed on the lower surface. A third foliar fraction (≈30%), which showed high rain fastness but was readily extracted by methanol, is probably buprofezin absorbed to the leaf wax or to the inert residue of the formulation. Results strongly indicate that buprofezin acts by contact, inhalation, or both.