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The root-feeding flea beetle, Longitarsus flavicornis, was released in Australia in 1979 for the biological control of ragwort, Senecio jacobaea. Although the agent has since become well established at many sites, its impact on ragwort populations is noted to vary between years, geographic locations, and under different land-management techniques. This paper addresses the possibility that these variations in efficacy are related to basic soil and climate features of the sites. Soil characteristics and climate were compared between sites where the flea beetle had controlled ragwort and sites where it has had minimal impact on ragwort populations. The only factors that varied significantly between successful and unsuccessful sites were salinity and the abundance of plant roots in the A1 soil horizon. Unsuccessful sites were found to have a higher average salinity and a lower abundance of plant roots compared to successful sites. Multivariate ordination revealed no pattern grouping successful and unsuccessful sites. [Copyright &y& Elsevier]

Wick-wiping of herbicides in summer to kill flowering ragwort and reduce seed production is the current recommendation for the integration of herbicide use and biological control using Longitarsus flavicornis (Stephens) in Tasmania, Australia. Ragwort rosettes remain undamaged by wick-wiping and their survival provides a food source for L. flavicornis. This recommendation has always been based on the assumed negative impact of boom-sprayed herbicides on L. flavicornis without the availability of supporting data. Vacuum collections at a site at Franklin, Tasmania, showed that over 80% of adult L. flavicornis occurred on rosettes rather than on flowering plants. Glasshouse choice-trials of L. flavicornis oviposition behavior showed that over 95% of eggs were laid around rosettes rather than on flowering plants. These results now provide supporting evidence for the validity of the current integrated control strategy for ragwort. Reasons for the habitat preference by L. flavicornis of rosettes over flowering plants and the implications for the survival and increase of this biological control agent are discussed. [Copyright &y& Elsevier]