Oviposition and feeding behaviour by the vine weevil Otiorhynchus sulcatus on red raspberry : effects of cultivars and plant nutritional status

The vine weevil Otiorhynchus sulcatus is a major pest of horticultural crops worldwide, with root-feeding larvae causing most damage. Adult oviposition aboveground may therefore influence levels of damage as the larvae are relatively immobile after oviposition. The present study investigated feeding and oviposition behaviour on red raspberry Rubus idaeus using intact plants, ensuring that choices reflected the realistic differences in cultivar appearance and chemical composition. Previous studies investigating vine weevil feeding and oviposition on other crops have used excised plant material, which may inadvertently influence behaviour. Adult weevils significantly preferred to feed on particular cultivars in the choice experiment (e.g. Tulameen), although they consumed significantly more foliage (0.22-1.03 cm2/day) on different raspberry cultivars (e.g. Glen Moy, Glen Rosa and a wild accession) in no-choice situations. In choice experiments, weevils tended to avoid laying eggs on some cultivars (e.g. Glen Moy and the wild accession). The number of eggs laid (1.91-4.32 eggs per day) did not, however, differ significantly between the cultivars in a no-choice situation. Foliar nitrogen and magnesium concentrations were positively, although weakly, correlated with the total number of eggs laid. The present study highlights the importance of considering both choice and no-choice tests when assessing crop susceptibility to attack because weevils may avoid feeding on certain cultivars (e.g. Glen Moy) when given a choice, although this would cause significant damage to such cultivars if they were grown in monoculture (i.e. when there is no alternative).