Eucalypt insects - pests at home and abroad: the growing need for a coordinated approach to biological control

Abstract

Pests of Australian origin are a worldwide problem following the large-scale expansion of eucalypt plantations over the last few decades. In the absence of co-evolved natural enemies, Australian eucalypt herbivores can reach devastating population densities and rapidly colonise new regions. Introductions of invasive Australian pests to the major eucalypt plantation growing regions of the world have accelerated over the past 10 – 20 years - a trend likely to continue as volumes of trade and movements of people increase. Not only has the rate of introductions increased, but the speed with which they have subsequently invaded other regions following the initial introduction has also increased. Examples include the gall wasps Leptocybe invasa and Ophelimus maskelli and the sap-sucking bug Thaumastocoris peregrinus, insects which were unknown (L. invasa) or poorly known (T. peregrinus) in Australia prior to being found overseas. Together, their speed of invasion and the lack of basic biological knowledge on these insects compromise efforts to coordinate and optimise biological control programs around the world. This highlights the inadequacy of the current piecemeal approach to the identification, evaluation, selection, collection and shipping of natural enemies to affected regions and emphasises the need for a coordinated approach. Within Australia, such herbivores also exploit artificial monocultures represented by eucalypt plantations and reach damaging population densities before natural enemy populations can respond. Furthermore, overseas herbivores and pathogens have adapted to colonise and exploit eucalypt plantations, presenting a significant risk to plantation productivity there, and a significant biosecurity threat to Australia. There are therefore complementarities between the needs of eucalypt growers overseas and in Australia in relation to managing pests through biological control and for monitoring future threats. An opportunity therefore exists to establish a ‘centre’ in Australia to research and assist in coordinating biological control efforts for both local and international eucalypt growers.