Sunflower as a trap crop for the European tarnished plant bug (Lygus rugulipennis)

The European tarnished plant bug, Lygus rugulipennis (Heteroptera: Miridae), inflicts serious damage to glasshouse crops, including cucumber, in which it causes distorted foliage, dead growing points and malformed fruits. In a research involving commercial growers, we tested the possibility of using a trap crop to control L.rugulipennis. We screened the attraction of sunflower and lucerne as trap crops using an olfactometer. Adults (females and males) were more attracted to the odour of either flowering sunflower or lucerne than flowering cucumber. In a glasshouse trial, potted flowering sunflowers were evaluated as a trap crop placed at the ends of each cucumber row. Although the trap crop showed much higher attractiveness than the cucumber crop, this effect was not sufficient to provide an acceptable level of control according to the commercial growers. The growers suggested developing artificial sunflower odour as a more efficient lure for removal trapping. As a first step in this development, we tested the attraction of the headspace odour collected from sunflower in olfactometer trials. Sunflower headspace attracted a higher number of adults compared to a blank or a flowering cucumber. The sunflower odour was analysed by gas chromatography coupled to mass-spectrometry to determine compounds possibly involved in L.rugulipennis attraction. The chemical analysis of the plant odour showed a well-defined differentiation between sunflower and cucumber, with a number of monoterpenes released exclusively by sunflower. This, plus an emission rate from sunflower being at least four times more abundant, opens the possibility of using synthetic sunflower volatiles to attract L.rugulipennis within a cucumber background.