Biological aspects of Gonipteris scutellatus, an important pest of Eucalyptus globulus plantations

Gonipterus scutellatus, a eucalypt weevil native to south eastern Australia, is a major pest in Eucalyptus globulus plantations through out the south west of Western Australia. Knowledge of this pest and it's interactions within eucalypt plantations has been well documented in South Africa, Southern Europe and in both north and south America, but little work has been done on its interactions with the E. globulus plantations and native forest in the south west of Western Australia. This honours study aimed to understand various aspects of the biology of G. scutellatus and of the interactions that occur between G. scutellatus and the E. globulus trees that have been planted as plantations in the south west region of Western Australia. Three major outcomes were developed from this study concerning sexual size dimorphism, eucalypt palatability, and diapause. These outcomes are, A mathematical equation was developed that allows the identification of the gender of an unknown G. scutellatus by using the results of the measurements of five morphological characteristics. After entering the measurements into an equation developed for male weevils and an equation developed for female weevils, the equation with the higher result identifies the weevil's gender, thus allowing field identification of the weevils gender without the need for dissection. Eucalyptus marginata, E. diversicolor, E. gomphocephala, E. rudis and Corymbia calophylla, are the dominant tree species in the South west region, and are all endemic to Western Australia. These species were all thought of as being unsusceptible to attack by G. scutellatus, but they were shown to be as palatable as E. globulus when no alternate food source was available. This may have huge implications for plantation harvesting and or removal practices. Temperatures of 20°C, irrespective of photoperiod, had a significant effect on possible diapause induction. However, Further work is required before it can be ascertained if low temperatures induce diapause in G. scutellatus occuring in Western Australia