Individual study: A systematic review to assess if cinnabar moth Tyria jacobaeae and ragwort flea-beetle Longitarsus jacobaeae are effective biological control agents of common ragwort Senecio jacobaea
Roberts P.D. & Pullin A.S. (2005) Effectiveness of the control of ragwort (Senecio) species: “Can biological control by the use of natural enemies effectively control Senecio jacobaea (common ragwort)?”. CEE review 04-004 (SR5b) report.
Two invertebrates native to Europe that feed on common ragwort Senecio jacobaea, the cinnabar moth Tyria jacobaeae and ragwort flea-beetle Longitarsus jacobaeae, have been used in attempts to control common ragwort due to its potential to poison livestock and invasive nature in some areas. The larval food plant of the cinnabar moth is S.jacobea and the closely related groundsel S.vulgaris. Both adults and larvae of the ragwort flea-beetle feed on ragwort but it is the larvae which cause extensive damage or death as they feed inside the stem and roots of the plant.
A systematic review (see: www.cebc.bham.ac.uk for methodology) was undertaken to evaluate evidence for the effectiveness of cinnabar moth larvae and flea-beetles (including a combination of both) in the control of common ragwort.
Evidence suggests that although the overall density of common ragwort plants is not significantly reduced by cinnabar moth larvae, they detrimentally affect the plants reproductive ability by reducing production of capitula and seeds. However, there is considerable variability in the reduction of ragwort using cinnabar moth larvae and some sites even exhibited increases in ragwort. Flea-beetles are more effective, with all sites showing major declines averaging 96.5% in ragwort densities. The combination treatment using both insects shows the greatest potential for effective control of ragwort with an average decline of 99.5% (in the five studies examined) in ragwort densities.
These results should be viewed with caution due to uncertainty of confounding effects and the reduced methodological quality used to obtain the original datasets. The authors recommend additional trials over at least a two-year time period to further investigate the effectiveness of all three treatments on common ragwort control.
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