Farm Forestry New Zealand
PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND
New Eucalyptus leaf beetle detected in New Zealand
A new Eucalyptus leaf beetle has been found to be well established following a recent investigation by Biosecurity New Zealand
In October 2024, a suspected new to New Zealand Eucalyptus leaf beetle was encountered by a member of the public in Whakarewarewa forest, Rotorua and reported to Scion. A Scion entomologist identified this as Paropsisterna morio, a new to New Zealand leaf beetle, and reported this to Biosecurity New Zealand (BNZ).
Adult Paropsisterna morio. (Source: Biosecurity New Zealand)
Larvae Paropsisterna morio. (Source: Biosecurity New Zealand)
The subsequent BNZ Investigation, which included a field visit alongside Scion specialists to the area that it was first detected, found numerous adults and larvae, which were confirmed as P. morio. Subsequently further detections have been confirmed from other locations in Rotorua and in Hamilton as well.
In February 2024, BNZ investigated a report by a kiwifruit grower of an unusual beetle detected on a kiwifruit plant. This was reported to Kiwifruit Vine Health, the kiwi fruit sectors biosecurity agency, who subsequently reported it to BNZ. An investigation at the time found no further signs of the beetle or its larvae, and no obvious signs of leaf damage were observed either. However, it did find that a grower took a photo of a very similar looking beetle in Nov 2023 which was likely to be the same species. The beetle could not be identified to species using morphological techniques as only a single specimen was detected, and it was the wrong sex required for species determination. Its species has subsequently been confirmed by using molecular techniques.
Biosecurity New Zealand’s investigation concluded that P. morio is widely established and that eradication is not feasible. Its cryptic and nocturnal nature means that the effectiveness of surveillance and control options are very limited. BNZ has concluded its investigation and is not planning any further action.
Why is it important
Unfortunately, P. morio is now too well established and widespread to eradicate which means that it is now part of the community of potential eucalyptus leaf beetle pests that we will need to contend with. BNZ’s investigation found little information on its biology or impacts in its native range that would suggest that it would be any more damaging than leaf beetles already present in NZ.
In 2018, the Forest Biosecurity Committee engaged Scion to prepare a report on “New Eucalyptus Pests and Diseases: what is the risk and how should we respond?” to inform consideration of response options to future detections of eucalyptus pests or diseases. This report concluded that introductions of Eucalyptus pests and diseases were expected to be ongoing given Australia is our closest neighbor, and that eradication was generally not a feasible or cost-effective option, except if the pest of pathogen was detected very early and its distribution was very limited.
Next steps
Dr Toni Withers, Scion, will be preparing a short technical article for Tree Grower on P. morio and the potential for exploring biological control options.
Brendan Gould, Director Biosecurity and Risk, NZFOA
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