Flower choices by raspberry beetles: cues for feeding and oviposition

Raspberry beetles, Byturus tomentosus, use raspberry as the host plant for feeding, mating and oviposition; the larvae are a major pest on the fruit. This study seeks reasons for their choices between flowers of different cultivars. Beetles showed consistent diurnal movements between different cultivars of raspberry, which were linked to differential behavioural patterns; they fed predominantly on Glen Clova canes in the morning and moved to Glen Prosen later in the day where oviposition behaviour was commoner and substantially more effective. Hence two closely similar cultivars of the same plant species received very different levels of flower damage (from adult feeding) and of fruit damage (from larval infestation). These patterns were linked to subtle differences in cues from the host plant; Glen Clova produces unusually copious nectar which may limit oviposition opportunities because of osmotic threats to eggs and larvae, whereas Glen Prosen has drier flowers for egg laying and apparently emits a short-lived volatile cue that principally attracts female beetles. Selective breeding of the host plant has therefore had unexpected side-effects on interactions with a major pest species, mediated by the behaviour of the insect, and perhaps accentuating natural behavioural preferences that serve to reduce competition between adult and larval stadia. Copyright 1998 The Association for the Study of Animal Behaviour.