The threat to Eucalyptus plantations from an emerging Tasmanian leaf beetle pest: Paropsisterna selmani (Coleoptera: Chrysomelidae)

A newly described eucalypt leaf beetle, Paropsisterna selmani Reid and de Little, endemic to Tasmania, Australia, required management in Tasmania for the first time in 2011 to protect Eucalyptus nitens plantations from severe defoliation. This species was discovered following its incursion and subsequent establishment in southern Ireland in 2007.

Field monitoring using sticky traps in eight E. nitens plantations around Tasmania was performed to compare the spatial and temporal population distributions of adult P. selmani with adult P. bimaculata and P. agricola over two summer seasons, 2009-2010 and 2010-2011. Populations of all three species were extremely variable between sites and between and within the two seasons. While P. bimaculata dominated at six of the eight sites throughout Tasmania, P. agricola had high populations at the three most northerly sites. Adult P. selmani were trapped at all sites but were the dominant leaf beetles at one site and were relatively common at two other northerly sites.

During the longer trapping period in the second season, all three species showed two population peaks: one in spring (November-December) following emergence of adults from overwintering, and a second in late January–February of a second generation of adults. Heavy egg-laying followed the first but not the second adult population peak. At the two sites with the largest P. selmani populations, the peak spring flight of P. selmani adults occurred at least two weeks earlier than that of P. bimaculata and P. agricola, and the second flight peak was at least two weeks later than that of these species.

A new pest with a population phenology that differs from that of existing plantation pests could have important implications for the success of an Integrated Pest Management program designed to protect plantations from defoliation. Field records of P. selmani since it was first recorded in 1979 suggest that this species is increasing in abundance in Tasmania. Management of this species has been required since 2011 to prevent economic damage to plantations. This newly emerging plantation pest feeds on a range of Eucalyptus hosts, including the adult-phase foliage of the plantation species E. nitens, and poses new problems for plantation management in Australia, as well as increasing the threat of invasion into overseas eucalypt plantations, as already demonstrated in Ireland.