Selecting biological control agents
Selecting effective agents
Selecting more effective agents
The approach for insect biocontrol
Hoddle (2004) noted that the historical success rate for programmes against weeds is three times that for insect pests, and that one reason for this might be the long held requirement for detailed and costly host-range evaluation for weed control agents, leading to a more thoughtful assessment of which agents are likely to work. Certainly, the recent literature suggests that the theoretical basis for selecting biological control agents for weeds outlined here appears better developed than that for invertebrates, although the principles discussed above are equally relevant to the biological control of invertebrates. Barlow (1999) elegantly reviewed the use of 50 models in biological control practice and concluded that improving decision-making by predicting the effect of proposed control agents before introduction was still a largely futuristic goal. The greatest gap in base data appears to be the searching ability, dispersive behaviour and spatial spread of agents, parameters than can only be accurately estimated in the agent's native range. However, he suggested two approaches that could improve agent selection in the absence of such data:
- test a range of scenarios covering the unknown parameters, such as parasitoid searching efficiency;
- using a population dynamics model for the pest, compare the theoretical effects of agents on different life stages of the pest to identify the presence and intensity of density-dependence in the life cycle of the pest. This is analogous to the approach suggested by van Klinken and Raghu (2006) and Briese (2006) for assessing control agents for weeds.
Mills and Getz (1996) also reviewed and critiqued the models available for measuring the efficacy of parasitoids.
Barlow N.D. (1999). Models in biological control: a field guide Pp. 43-70 In: Theoretical approaches to biological control, B.A. Hawkins and H.V. Cornell (Ed.) Cambridge University Press UK.
Briese D.T. (2006). Can an a priori strategy be developed for biological control? The case for Onopordum spp. thistles in Australia. Australian Journal of Entomology 45: 317-323
Hoddle M. (2004). Restoring balance using exotic species to control invasive exotic species. Conservation Biology 18: 38-49
Mills N.J. and Getz W.M. (1996). Modelling the biological control of insect pests: a review of host-parasitoid models. Ecological Modelling 92: 121-143
van Klinken R.D. and Raghu S. (2006). A scientific approach to agent selection. Australian Journal of Entomology 45: 253-258
For weed biocontrol
Characteristics of successful agents