Farm Forestry New Zealand
PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND
Gum leaf skeletoniser response continues
From Biosecurity Issue 24, December 2000.
Gum leaf skeletoniser (Uraba lugens) caterpillars were detected at the Omanu Golf Course in Mt Maunganui during MAF Forest Biosecurity’s seventh full survey, conducted in October this year.
The Australian pest was first discovered in June 1997 at the Mt Maunganui Golf Course.
All eucalyptus trees within 1.5 kilometres of the Omanu Golf Course, as well as host trees on Mt Maunganui Golf Course, Waitui Reserve and Berescourt Place were included in the October survey undertaken by forest health advisers (VIGIL). Of the 375 host trees inspected, a single silver dollar tree (Eucalyptus cineria) was found to harbour the caterpillars.
The tree was about 300 metres east of the last known area of infestation, detected a year earlier in October 1999. Following detection of the caterpillars, the ground was immediately treated around the infested tree and nine neighbouring host trees were also sprayed with the synthetic pyrethroid insecticide, deltamethrin (trade name Decis Forte).
The discovery of the insect within the boundaries of the Omanu Golf Course is not, in itself, surprising. All gumleaf skeletoniser finds over the last two years have been within 300 metres of the infested tree.
The latest find may be attributed to a residual population of adult moths relocating from a previously infested shelterbelt located nearby. As directed by MAF Forest Biosecurity, the shelterbelt trees were destroyed in December 1999. Surviving moths may have flown to host trees within the immediate vicinity when the shelterbelt was destroyed.
The latest survey indicates that the gum leaf skeletoniser has not extended its range outside the known infested area. As such, eradication is a distinct possibility. Further surveys have been scheduled for 2001.
Closely related to the white spotted tussock moth that was eradicated from central Auckland in 1998, painted apple moth larvae are clothed with dense hairs arranged in tufts, and sport a row of distinctive white ‘tussocks’ along their back.
Mark Ross, National Adviser, (Forest Pest Surveillance and Response), MAF Forest Biosecurity
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