Uraba Lugens, gum-leaf skeletoniser
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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.
Forest Health News 180, January 2008.
The eucalypt feeding pest, Uraba lugens (gum leaf skeletoniser) (Nolidae) from Australia, has been present in New Zealand since 1992 and is continuing to extend its range. Just before Christmas 2007, eggs and larvae were found on a Eucalyptus botryoides at the organic recycling centre in Hamilton. Previous records from the Waikato were from a pheromone trap catch in Meremere in 2006, close to the border with the Auckland Region, and a call in from the public with a caterpillar found at the Huntly Power Station in October 2007. In a previous update in this newsletter (FHNews 169: 1) the arrival of U. lugens in the Waikato was noted; it was also reported from Northland but this location record was an error. The most northerly location for U. lugens to date is from a pheromone trap catch in 2006 at Pakiri, just north of Warkworth in the Rodney District of Auckland. No further records have been found from the Rodney District of Auckland, or further north, since 2006.
The U. lugens population in Auckland is currently starting to pupate. This generation over summer was considerably smaller than the previous one last winter. Simon Cook of Auckland City Council noted a that a tree with 30% defoliation in the winter generation of 2007 suffered only 5% defoliation in this summer generation. It appears that the population is highly variable generation to generation. Reports from colleagues in Adelaide suggest that U. lugens populations in that part of Australia have been very low for the past two summers, following a large and damaging population in the 2005/06 summer. Similar fluctuations are expected here in New Zealand.
Research into biological control for U. lugens (funded by the Sustainable Farming Fund) has made some significant advances this summer and raised many new questions. Experiments have been conducted to test the willingness of one potential parasitoid species, Cotesia urabae, to attack a number of New Zealand caterpillars. Unfortunately although preliminary data suggest that the wasp is capable of attacking some species, it remains to be seen if this attack is successful (i.e., results in the death of the caterpillar), or is ecologically significant. Analysis is still under way, and further experiments will be done to answer these questions before ruling out this species as a potential biological control agent.
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(Scion is the trading name of the New Zealand Forest Research Institute Limited.)