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 many conventional insecticides. Novel strategies for control are required and these may incorporate compounds whose lethal and sublethal effects have gone unremarked. Although most commonly employed as an insecticide synergist, piperonyl butoxide alone was lethal to predominantly second instar nymphs of the cotton whitefly, B. tabaci at LC(50)s of between 60 and 600 ppm, depending 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 known resistance mechanisms or enzyme banding patterns. Residues of piperonyl butoxide alone were toxic to adult B. tabaci at c. 2000 ppm which was similar to the toxicity of paraffin oil. Piperonyl butoxide also increased developmental 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 not reduce the feeding activity of insects surviving treatment. Such effects offer scope for incorporating this compound into resistance management programmes, especially in conjunction with natural enemies (e.g. parasitoids active specifically against immature hosts).