BIOLOGY OF <i>LONGITARSUS FLAVICORNIS</i> (STEPHENS) (COLEOPTERA: CHRYSOMELIDAE) AND ITS EFFECTIVENESS IN CONTROLLING RAGWORT (<i>SENECIO JACOBAEA</i> L.) IN TASMANIA

Abstract

Abstract Monitoring established field populations of an introduced French strain of Longitarsus flavicornis in Tasmania in 1985/86 showed that newly‐emerged adults were first recorded in early December, with peak emergences occurring in January. Oviposition commenced in January, first instar larvae were recorded from mid‐February and the first pupae were collected in early November. Laboratory studies suggested that eggs laid in the field in late autumn may not hatch until the following spring. Evidence is presented that prevailing weather conditions may have initially restricted establishment and spread of L. flavicornis in some areas. Ragwort density was reduced at 2 monitored sites where L. flavicornis was established. Ragwort populations, which initially consisted of plants with both single and multi‐crowns, and shoots from a range of size and development classes, were replaced by populations dominated by plants with single crowns and small rosettes. These observations indicate that L. flavicornis can be effective in controlling ragwort.