RESUMEN
The emergence of resistance mechanisms to, and revocation of, many insecticides used in the control of the polyphagus aphid pest, Myzus persicae (Sulzer), has increased the pressure to develop novel approaches for the control of the pest in many crops. Kaolin-based particle films provide a physical barrier against insect pests and show considerable potential for controlling M. persicae. We conducted a series of laboratory experiments to investigate the mode of action of kaolin against aphids. The material appeared to have no direct effect on M. persicae; spraying adult aphids with aqueous kaolin suspension had no significant impact on their subsequent survival or reproduction on untreated plants. Similarly, when aphids were placed on kaolin-treated host-plants (Brassica oleracea), their performance (survival, growth rate and reproduction) was not significantly different from aphids on untreated plants. However, when M. persicae were given a choice between kaolin-treated and untreated (or water solvent-treated) leaf areas, both adults and nymphs exhibited a significant preference for non-kaolin-treated host-plant material. Rejection of kaolin-treated plant material occurred very rapidly (within 20 min) and this behavioural effect may be related to the efficacy of kaolin in controlling aphids under field conditions.