Farm Forestry New Zealand
PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND
Uraba, the battle begins, December 2003
From Forest Health News 136, December 2003.
The gumleaf skeletoniser, Uraba lugens , was first discovered in the Auckland area in August 2001, at Onehunga (FHNews 110: 1). Despite attempts at eradication, a new population centre of this Australian pest was discovered earlier this year, centred in Favona and Mangere suburbs across the Manukau Harbour (FHNews127: 1-2). The full extent of the infestation in South Auckland has now been determined using ground surveys and by the deployment of synthetic sex pheromone traps. Uraba currently occupies an area stretching from Devonport in the north, Mt Albert in the West, and Howick in the East, to Wiri in the South. With such a widespread distribution it became apparent that eradication was no longer an option and that a new approach is needed. A recent release by the Ministry of Agriculture and Forestry (MAF) announced that the government has approved funding for the first of two years of a long-term management programme for the gumleaf skeletoniser. A key emphasis of the new management approach will be on research to supply the essential information required for the successful control of the U. lugens population within NewZealand.
Funding has been awarded to Forest Research, among other science providers, to carry out investigations within a number of key areas. Work will be undertaken to determine the life cycle of the pest and its propensity for expanding its range under the environmental conditions prevailing in New Zealand and the types of parasitoid and predator it may encounter. The tree species most at risk from Uraba will be resolved through testing both in the field and laboratory, and the impact of pest damage on subsequent tree growth will be explored. Research will also include options for control and management. Parasitoids and pathogens with potential for controlling U. lugens will be studied in Australia, in the hope that biological control agents may be identified that will be sanctioned by the Environmental Risk Management Authority (ERMA) for release in plantations by forest managers and landowners in the future. In the meantime effective spray application remains a necessary management tool, and insecticides containing ingredients such as Bacillus thuringiensi var. kurstaki (BtK) or spinosad, which are both specific against moth species, will be tested for their effectiveness in different formulations. The ultimate success of research and management will depend on reliable population monitoring, and studies will be conducted into the effectiveness of the synthetic pheromone trap as a monitoring tool, and also for possible use for mass trapping in the future.
In the longer term, the responsibility for the management of Uraba lugens will pass to the affected forest managers and landowners. MAF will assist this process by communicating the information obtained from research through avenues such as educational field days and computer programmes, and by means of publications such as leaflets and handbooks.
Meanwhile, MAF continues to maintain the present “restricted area” in order to limit the spread of this unwanted pest from the current infested zone in Auckland.
Toni Withers, ForestResearch
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