Methyl isonicotinate induces increased walking and take‐off behaviour in western flower thrips, Frankliniella occidentalis

Abstract

AbstractTimely detection of western flower thrips (WFT), Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is important to help prevent economic damage to crops. Coloured traps are commonly used for thrips monitoring and their efficacy can be markedly improved with the addition of semiochemicals such as methyl isonicotinate (MI). However, the behavioural response of thrips to these compounds is poorly understood. In leaf/petal disc laboratory experiments the effect of MI on adult female WFT was examined with respect to walking and take‐off behaviour. Clean air or air with MI was blown over the leaf/petal discs at an angle of 30° via a glass pipette connected to a wash bottle containing a cotton dental roll with or without a defined amount of MI. At airspeeds of 0.6–1.2 m s−1 and at doses of 1, 10, 50, 100, and 1000 μl (equivalent to indicative concentrations of 1.7, 4.5, 7.3, 8.8, and 14.9 ng MI l−1 air blown over the leaf discs), WFT spent a greater proportion of time walking on chrysanthemum leaf discs in the presence of MI than the non‐attractive thrips compound β‐caryophyllene or clean air. Western flower thrips showed a dose‐dependent take‐off response to the thrips attractant MI, but not to β‐caryophyllene (virtually no take‐off). At 100 μl of MI (8.8 ng l−1 air), WFT spent a greater proportion of time walking on host plant tissue than in clean air, depending on plant disc substrates. Furthermore, WFT took off more often from plant discs exposed to an air current containing MI than from those exposed to clean air. Western flower thrips exposed to MI took off at a similar rate from chrysanthemum leaves, chrysanthemum flower petals, and sweet pepper leaves, but much less readily from bean leaves. The results show that MI stimulates walking and take‐off behaviour for adult female WFT under these experimental conditions and these responses are dose‐dependent and mediated by the host plant. These results are placed in the context of previous research on the behavioural response of thrips to semiochemicals and their implications for thrips pest management are discussed.