Synergistic manipulations of plant and insect defences

BACKGROUND It has been demonstrated previously that cis-jasmone acts as an elicitor of plant defence mechanism(s) by inducing secondary metabolism. It has also been demonstrated that temporal synergism can result in hypersensitive insect pests due to the inhibition of metabolic enzymes. RESULTS Laboratory bioassays demonstrated that pre-exposure of insects by piperonyl butoxide followed by cis-jasmone treatment of crops, reduced Aphis gossypii on cotton by 80% and Myzus persicae on sweet pepper by 90%. By microencapsulating the cis-jasmone and combining with piperonyl butoxide, Bemisia tabaci on tomatoes was reduced by 99%. A field trial with microencapsulated cis-jasmone combined with piperonyl butoxide resulted in a comparable reduction of whitefly egg numbers to that given by the registered rate of imidacloprid, with efficacy of 89% and 93%, respectively. CONCLUSIONS If insect defence enzymes are compromised by piperonyl butoxide whilst plant defence is primed by cis-jasmone, there are possibilities of an insecticide-free method of controlling insect pests. The success seems largely dependent upon the toxicity of the plants' secondary chemistry.