Dicranosterna on blackwood - research into biocontrol
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Formerly known as the Forest Research Institute, Scion has been a leader in research relating to forest health for over 50 years. The Rotorua-based Crown Research Institute continues to provide science that will protect all forests from damage caused by insect pests, pathogens and weeds. The information presented below arises from these research activities.
From Forest Health News No. 105, March 2001.
Over the last few years the introduced Australian beetle Dicranosterna semipunctata has been causing moderate defoliation of plantations throughout the greater Auckland region (Forest Health News, No. 79). To address this issue, consideration is being given to potential biological control options before D. semipunctata becomes too widespread and even more of a problem. Possible biocontrol agents include two species of parasitoid wasps, Enoggera polita and a species of Neopolycystus, which were found attacking D. semipunctata eggs during an investigation in northern New South Wales in November 1999. The Environmental Risk Management Authority (ERMA) requires us to demonstrate a good understanding of the biology of these egg parasitoids, before approving the importation of new organisms into quarantine. So in January and February this year, further research was undertaken in Australia to obtain essential information on the distribution of D. semipunctata and the life cycles of the parasitoids. The Australian distribution of D. semipunctata extends from Victoria through to northern NSW, with greatest numbers occurring on the tablelands in from the coast. Rearing the parasitoid wasps in the laboratory demonstrated that the life cycles are comparatively short, the period between egg and adult being completed in just over a week and half. It was also determined that the adults can be kept alive for up to five weeks. Between 33 -60% of D. semipunctata eggs were found parasitised in the field. Attack by both egg parasitoids is restricted to the coleopteran sub-family Chrysomelinae, which includes exotic genera such as Chrysophtharta, Paropsisterna, Trachymela, and Paropsis (e.g. the introduced eucalypt tortoise beetle, P. charybdis ). No hyperparasites were found in any of the D. semipunctata eggs, and we are optimistic about obtaining clearance for importing the parasitoids into quarantine. However, all the issues on the biocontrol and current pest status of D. semipunctata will be fully reviewed before an import application is submitted to ERMA.
(Clive Appleton, Forest Research)
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