Phenology of Eucalyptus weevil, Gonipterus scutellatus Gyllenhal (Coleoptera: Curculionidae), and chrysomelid beetles in Eucalyptus globulus plantations in south‐western Australia

Abstract

Abstract1 In south‐western Australia, Eucalyptus globulus plantations are defoliated by a complex of beetle species, yet only scant information exists on these species under such climatic conditions. To improve management of these defoliating beetles in the region, canopy fogging and shoot clipping were conducted in plantations between 1999 and 2002 to identify and document the phenology of the beetle species present.2 Eucalyptus weevil, Gonipterus scutellatus, was the most common and destructive defoliating beetle. Gonipterus scutellatus undergoes one principal generation each year with a lesser second generation or cohort in some seasons, which contrasts greatly with reports of two to four annual generations for the species in other regions. This limited reproduction by G. scutellatus may be due to the limited availability from summer onwards of new flushing foliage, which is essential for feeding and oviposition.3 Several species of chrysomelid beetles were collected in plantations, but these were present in much lower numbers than G. scutellatus and were only a minor concern. However, some species, such as Chrysophtharta variicollis, appear to be capable of developing short‐lived outbreaks.4 A diverse suite of natural enemies was fogged from plantations but they were significantly less abundant than defoliating beetles and are not likely to provide significant control of beetles.5 In terms of managing these defoliating beetles, monitoring and control should focus on G. scutellatus, and be conducted during spring when most damage occurs.