COMPARISON OF DAMAGE TO EUCALYPTUS CAUSED BY AMORBUS-OBSCURICORNIS AND GELONUS-TASMANICUS

Amorbus obscuricornis (Westwood) and Gelonus tasmanicus (Le Guillou) ( Heteroptera: Coreidae) are specific to Eucalyptus (Myrtaceae). A. obsc uricornis feeds almost exclusively upon apical shoots and causes a cha racteristic wilting and necrosis. By comparison, the feeding activitie s of G. tasmanicus result in no obvious phytotoxicosis. Salivary gland extracts from both species exhibited sucrase activity but no pectinme thylesterase (PME) activity. Saliva from A. obscuricornis also exhibit ed considerable oxidase activity. Sucrase activity was significantly h igher in extracts derived from C. tasmanicus than from A. obscuricorni s, but this could not explain the observed differences in phytotoxic s ymptoms. It is suggested that differences in plant damage are attribut able to the site of feeding activity (i.e. young versus mature tissue) , which predetermines the reactivity of host tissues, and/or the quant ity of salivary enzymes injected.