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26 February 1997
An insect identified as a European species of sawfly (Nematus oligospilus) has been found on a property in the Auckland suburb of Onehunga.
The sawfly is thought to infest mostly species of willows, and occasionally poplars. Willows are mainly used in New Zealand for shelter belts, to provide shade for stock and to prevent erosion.
The larvae of this species eats the willow leaves, leading to defoliation. More information on the long term effects of such defoliation on the trees is being sought.
This sawfly is native to Britain and Ireland and has recently established in South Africa. The origin of the infestation in New Zealand is unknown at this stage, but will be investigated.
Although it is referred to as a fly, it belongs to the 'bees and wasps' group of insects, and its larvae look more like caterpillars. The larvae have dull, dark green bodies, similar to that of the common white butterfly caterpillar, and light yellowish-brown heads with a distinctive dark triangular mark on the front. The adult sawflies are light green.
A formal survey involving staff from the Ministry of Agriculture and the Ministry of Forestry will be undertaken to determine how widely it has spread. The results, which should be available at the end of next week, will assist in determining any further action. Preliminary investigation following identification of the insect by Landcare Research indicates that the infestation is not confined to the property on which it was found.
Members of the public who suspect they have found sawfly larvae on their willow trees should contact staff at the Ministry of Agriculture's Plant Protection Centre at Lynfield in Auckland (09) 626 6026.
Media inquiries to:
Dr Ruth Frampton, National Advisor, Plant Pest Surveillance (025) 350 801
Debbie Gee, Manager, Corporate Communications (04) 474 4258