LAUSR

BACKGROUND Sweetpotato weevil, Cylas formicarius (Fabricius) attacks stems and storage roots of sweetpotato, Ipomoea batatas and is a major pest of this globally significant crop. To minimise the immigration of weevils into sweetpotato fields from nearby donor habitat, we assessed scope for a barrier plant approach. Here we report a novel, two-stage, multiple choice olfactometer method to screen candidate barrier plant species and a field study of the effects of shortlisted barrier plants of weevil movement and plant damage. RESULTS Initial work established that a combination of sweetpotato foliage and storage root was significantly more attractive to adult C. formicarius than either tissue alone in the distal chamber of choice arms. Among 15 candidate barrier plant species in intermediate chambers in arms, spring onion, oregano, chilli, basil, sweetcorn, fennel, lime mint and lemongrass significantly reduced passage of C. formicarius. Of these sweetcorn and lime mint significantly reduced the numbers of oviposition holes in sweetpotato storage roots. A field study showed basil and chives were effective barrier plants for reducing weevil damage to sweetpotato storage roots. CONCLUSION Our method has utility for screening additional candidate plants and suggests that weevil dispersal and subsequent oviposition are affected by passage through some plants, suggesting scope for barrier plants to contribute to the management of this major pest. This article is protected by copyright. All rights reserved.