Ecofriendly synergists for insecticide formulations (EcoSyn): evaluating the potential of synergist/insecticide applications to select for resistance compered with application of insecticide alone

Insecticide synergists increase the lethality and effectiveness of insecticides by inhibiting the metabolic systems that would otherwise break them down. Synergists therefore have particularly utility in overcoming metabolic resistance and it has been suggested their use may also delay the development of resistance. To explore the latter, field populations of the peach potato aphid, Myzus persicae and whitefly Bemisia tabaci were selected over 8-12 generations with a pyrethroid (alpha-cypermethrin) and neonicotinoid (imidacloprid) both alone and in combination with piperonyl butoxide (PBO - an inhibitor of esterases and P45Os). All four treatment regimes resulted in a significant increase in resistance, however, both thiacloprid+PBO and alpha-cypermethrin+PBO gave lower levels of resistance than when insecticide was used alone. This finding suggests that when PBO is used in combination with insecticide it may slow the development of resistance, possibly by inhibiting the evolution of P450-mediated and/or esterase-mediated resistance. Replication of this study at the field-scale is now required. The fully phenotyped insect material generated from these experiments will allow differentially expressed genes to be identified betweer selected and unselected strains and these to be compared between strains selected with and without PBO.