Pea odorants guide host finding behaviour in pea moth: a new strategy for insect management?

Abstract: The pea moth Cydia nigricana (Lepidoptera: Tortricidae) is a major pest in pea growing areas. Alternative pest control techniques are needed since efficient control options are scarce. A strong correlation between the seasonal flight period of C. nigricana and the phenology of the pea plant Pisum sativum (Fabaceae) has been shown in field studies in Northern Hesse, Germany, in the years 2006-2008. In our current studies we are investigating the olfactory space between the pea moth and pea plant, aimed at the identification of volatile cues encoding host recognition and host finding in pea moth females, and the use of these volatile compounds for management of the pea moth. In dual-choice experiments in insect cages, the preference between potted pea plants of different phenological development stages was tested, using male and female C. nigricana (mated and non-mated). Mated females clearly prefer flowering pea plants, whereas non-mated females and males showed no preference. In wind tunnel experiments the upwind orientation of C. nigricana towards the odour of pea plants of different phenological development stages was tested, using pea plants (A) and headspace collections of pea plants (B) as the odour source. In both wind tunnel set ups (A and B), the preference of mated females for the pea flower has been confirmed and additionally, strong attraction of mated females for the late bud stage was recorded. Overall, the flower and the late bud stage of P. sativum seem to be the most important phenological development stages for the host finding behaviour of C. nigricana. In ongoing studies we are identifying and characterising the behavioural active volatile compounds of the pea plant, using GC-MS (coupled gas chromatography – mass spectrometry) and GC-EAD (coupled gas chromatography – electroantennographic detection).