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PESTS AND DISEASES OF FORESTRY IN NEW ZEALAND

Report on Paropsisterna beata at Waikanae, November 2016

November 2016.

The story goes that the NZ Forest Owners Association, as a partner in GIA (Government Industry Agreement), were informed by MPI of this beetle showing up in firewood sourced from Waikanae and transported to Upper Hutt during winter 2016. The beetle was confirmed to be P. beata (5 of them were found in the firewood), which confirms P. beata (Eucalyptus Leaf Beetle or ELB) has not been eradicated from New Zealand.

I spent half a day looking for P. beata at the location the firewood was sourced, along with an extensive search through Waikanae on eucalypt species known to be susceptible to chewing by Eucalyptus leaf beetles. I found plenty of Paropsis charybdis larvae and adults, but not one single P. beata.

This suggests to me one of two options. Either the beetle is well established in the Waikanae district (or greater Wellington region) and is not going to build up to damaging levels on Eucalyptus, or it has only just arrived in the area and is not yet well established. Eucalypt species at the incursion site include E. muelleriana, E. viminalis, E. botryoides, and E. saligna. P. charybdis (larvae and adults) was found on all species. Adjacent to that stand is a stand of E. nitens, with P. charybdis present. In Waikenae I found P. charybdis on E. leucoxylon and E. maidenii. No P. beata though, despite a very thorough search.

Given that MPI have decided to not even respond with a delimitation survey, this leaves industry (as a partner in incursion decision making) in a very awkward position, given that only a delimitation survey would allow MPI and industry to together become well enough informed for deciding on next steps regarding potential eradication and pest status.

The questions I have therefore are:

When P. beata was found in Whitemans Valley, on just a few trees, how abundant was it on those trees? And was it not found primarily on our most commercially important eucalypt species, Eucalyptus nitens? Seems there are more questions than answers regarding this forestry pest incursion that was supposedly eradicated, because at that time it was deemed to pose a threat to our plantation forest industry. So why does MPI now have no interest in it? I asked Don Hammond, a biosecurity and eradicatiion expert called in to the Whiteman's Valley eradication programme, about how abundant it was there and on what species of eucalypt it was found. He told me that it was originally discovered when someone felled a Eucalyptus nitens tree and found "hundreds of beetles on it". They were concerned and reported this to MPI. Don also found approximately 50 overwintering beetles in the bark of one tree and believes there was "quite a high infestation", but at that time limited to a small number of trees.

This suggests to me that Paropsisterna beata has the potential to become a serious pest of New Zealand's number one eucalypt plantation species E. nitens, but may currently be present only in one small pocket of eucalypts near Waikenae, that if ignored, will certainly establish. Seems only time will tell because MPI have decided it's here to stay.

Dean Satchell 29/11/2016

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