Balancing non-target risks - biological control agents and their alien plant hosts

Lantana camara

The highly invasive alien plant, Lantana camara in Australia and South Africa
(Photo credit: I, Mercewiki, CC BY-SA 3.0)

A recent study in the scientific journal, BioControl, proposes a framework that will improve decision making around the approval and release of biological control agents. The study by Paul Downey (University of Canberra, Australia and C·I·B Research Fellow) and Iain Paterson (Rhodes University) used examples from across the globe of alien plants that have biological control programs, to develop the framework.

One of the control options for managing alien plants involves the use of biological control agents (i.e. natural enemies such as insects and pathogens). Although the process of releasing such agents involves intensive testing, some effects on non-target organisms occur after the release of agents (i.e. to native or other alien plant species). Such non-target effects have raised questions over the science.

The non-target risk associated with the target alien plant is rarely considered; which in many cases is much greater than that posed by the biological control agent. At present, the non-target risk associated with the alien plants is not routinely or consistently considered in the approval process for the release of biological control agents. This situation has led to a range of inconsistencies and the adoption of a risk-averse approach.

“The biological control of the highly invasive alien plant Lantana camara in Australia was almost stopped due to a minor and temporary non-target effect to an alien ornamental tree, because the non-target effect from the insect was not balanced against the non-target effect from the alien plant. In Australia, Lantana threatens over 1300 native plants and 150 native animals. Thus, halting the Lantana biological control program over a minor and temporary non-target effect to another alien plant would have been a travesty to a very large number of native species under serious threat of extinction,” explains Paul Downey.

The framework proposed by Downey and Paterson, aims to improve this situation by providing a process for accounting for the risks from both the agent and target alien plant. This will lead to a better assessment of the actual risk and will provide a better justification for release and decisions around which alien plants should be a targeted for biological control.

Read the paper by Downey and Paterson

Downey, P.O. and Paterson, I.D. (2016). Encompassing the relative non-target risks from agents and their alien plant targets in biological control assessments. BioControl DOI 10.1007/s10526-016-9744-1

For more information, contact Paul Downey at or Iain Paterson at