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Background information

Biological control best practice

Selecting suitable targets for biological control

Much thought goes into selecting suitable biological control agents but it is initially important to ensure that the target is a suitable candidate for biological control. Sheppard (1992) pointed out that while success of weed biological control agents is only about 35%, if the analysis is based on the target weed rather than the agent, success can be as high as 65%. Fowler (2000) calculated that when funding and support is adequate, success rate for weed biocontrol is about 50-80%.

Charudattan (2005) discussed the factors involved in selecting a good biological control target for pathogens used for inoculative and inundative augmentative biological control. The author concluded that a target weed needs to have strong stakeholder interest, that there is a good candidate pathogen, and that biocontrol with the candidate pathogen will be as cost effective as other control options. It was also pointed out that weeds with good vegetative regeneration capacity, and species with genetic heterogeneity are more difficult to control with pathogens, but that annual, perennial and biennial weeds are equally good targets.

Although the EPA is concerned mainly with avoiding the release of new organisms that might be detrimental to natural ecosystems, to human health and well-being etc., they also have regard for the economic or environmental justification for the release. Since there is always a degree of uncertainty about environmental impacts, it is not worth taking that risk if the benefits are not shown to be potentially worthwhile.

For more detailed information on this topic see the section on Selecting Biological Control Agents.


Charudattan R. (2005). Ecological, practical, and political inputs into selection of weed targets: What makes a good biological control target? Biological Control 35: 183-196.

Fowler S.V. (2000). Trivial and political reasons for the failure of classical biocontrol of weeds: a personal view. Pp. 169-172 In: Proceedings of the International Symposium on Biological Control of Weeds, N.R. Spencer (Ed.) Bozeman, Montana.

Sheppard A.W. (1992). Predicting biological weed control. Trends in Ecology & Evolution 7: 290-291.