Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae) oviposition on seven naturally co-occurring Eucalyptus species

Gonipterus scutellatus is a significant insect pest of eucalypts in most countries where that genus has been introduced, but is usually only of minor significance in its native Australia. Because of this, much of the research on its biology and host preferences has been done outside Australia. This fact has the potential to produce misleading results as the insect may be forced to choose less preferred hosts, if normally preferred species are unavailable. In part of its native range, in Tasmania, oviposition of G. scutellatus was recorded on seven naturally co-occurring Eucalyptus species that were planted in even aged, replicated plots. Among the seven species were the economically important species, E. globulus and E. viminalis, which have been previously reported as highly preferred hosts. Within plots, oviposition occurred most commonly on three peppermint species (E. pulchella, E. tenuiramis and E. amygdalina) and was rare or absent on the other species (E. globulus, E. viminalis, E. ovata and E. obliqua). Of the peppermints, E. pulchella was the most preferred species for oviposition at this site. A low percentage of peppermints in mixed forest (containing these seven species) immediately adjacent to plots was always matched by low numbers of G. scutellatus eggs within plots; but high percentages of peppermints outside plots could either be matched by high or low numbers of eggs within plots. In the discussion, we suggest that previous studies of G. scutellatus host range may have been limited because the insect was not exposed to hosts it naturally encounters.