An unconventional use of piperonyl butoxide for managing the cotton whitefly, Bemisia tabaci (Hemiptera : Aleyrodidae)

Bemisia tabaci (Gennadius) is a pest of global importance which resists man y conventional insecticides. Novel strategies for control are required and these may incorporate compounds whose lethal and sublethal effects have gon e unremarked. Although most commonly employed as an insecticide synergist, piperonyl butoxide alone was lethal to predominantly second instar nymphs o f the cotton whitefly, B. tabaci at LC(50)s of between 60 and 600 ppm, depe nding on the strain. Formulated and technical material were similarly toxic and far more so than detergents. Some strains exhibited slight tolerance ( c. 3-10 fold) but there was no correlation of this with the presence of kno wn resistance mechanisms or enzyme banding patterns. Residues of piperonyl butoxide alone were toxic to adult B. tabaci at c. 2000 ppm which was simil ar to the toxicity of paraffin oil. Piperonyl butoxide also increased devel opmental times among B. tabaci nymphs at doses as low as 10 ppm and exerted a transient effect on oviposition. There was strong evidence that it did n ot reduce the feeding activity of insects surviving treatment. Such effects offer scope for incorporating this compound into resistance management pro grammes, especially in conjunction with natural enemies (e.g. parasitoids a ctive specifically against immature hosts).