Biocontrol – more cost effective than other control methods: case study on ragwort

A post-release economic analysis of the ragwort (Jacobaea vulgaris) biocontrol programme has estimated savings of at least $44 million annually to the dairy sector on ragwort control.

The highly effective agent released for ragwort has been the ragwort flea beetle (Longitarsus jacobaeae), released in 1983. The beetle has caused major declines in ragwort in most areas of NZ except wetter regions like the West Coast.

These savings estimates were achieved by surveying the 2005 costs of thirty-two West Coast farms control methods (where ragwort biocontrol was less effective at the time) to determine the cost of on-farm ragwort management. The data were then fed into a national benefit-cost analysis that predicted what the cost of ragwort control would be across New Zealand in the absence of biocontrol by the flea beetle. The costs of developing the biocontrol programme were calculated from historical reports and then inflation-adjusted back to the year they were incurred.

When comparing the overall biocontrol programme cost to the estimated control costs that would have occurred from the start of the programme in 1926 to 2015, New Zealand has seen a benefit: cost ratio of 14:1, i.e., for every dollar invested in ragwort biocontrol New Zealand has gained $14 in reduced ragwort control costs (in 2016 dollars). These savings are ongoing and sustainable, with no further investment needed.

The ragwort plume moth was introduced in 2005 and now provides good biocontrol in the high-rainfall regions, where the flea beetle has been ineffective. We are yet to determine the benefit: cost ratio for this agent. Anecdotal evidence has it that the benefits are, again in the tens of millions of dollars every year to the industry.

Biocontrol – more cost effective than other control methods: case study on ragwort

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