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Forest Protection SSIF research on species other than radiata pine 2019/20

By Toni Withers, Roanne Sutherland, Nicolas Meurisse, July 2020.

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Executive summary

Plantation species other than Pinus radiata (radiata pine), such as Douglas-fir and eucalypts, form an important part of a diversified forest estate. Eucalyptus species are planted over approximately 27,000 ha and contribute ~$40 million pa in hardwood chip exports. Throughout New Zealand the biggest threat to E. nitens plantations has historically been from the Eucalyptus tortoise beetle, Paropsis charybdis (Bain and Kay 1989). As part of the SWP partnership, Forest Protection also contributes research from its core funding (SSIF) to research on ensuring sustainable growth of diversified forest species. This report summarises progress made in the last financial year on Eucalyptus pest management, on the safety of biological control research (through research on the safety and lack of non-target impacts of biological control and the development of risk assessment models), and on a new polyphagous ambrosia beetle in Auckland, Xylosandrus crassiusculus.

New Zealand eucalypt forests are now under an additional threat to their health from the eucalyptus variegated beetle (EVB Paropsisterna variicollis). We report the name change due to synonymy to Paropsisterna cloelia, and update the prospects of locating a suitable biological control agent for Paropsisterna cloelia (= variicollis) from the collaboration with international entomologists. Ryan Ridenbaugh, University of Central Florida, has concluded his thesis during which he confirmed 37 rearings of Eadya annleckieae from Paropsisterna cloelia (= variicollis) that he collected from infested Eucalyptus globulus plantations in early December in Victoria, Australia. Fortuitously he also located two sites where Eadya daenerys were reared from Paropsisterna agricola and Paropsisterna m-fuscum (forming a new parasitoid-host association record). These collections will provide Scion with two possible sites (Mortlake and Heywood) in Victoria, Australia where we might be able to recollect E. daenerys for the biocontrol of P. charybdis in the future as Scion seeks a disease-free population for release in New Zealand.

Research was also completed on the likely geographic origin of P. cloelia (= variicollis) based on sequences from two gene regions of beetles from throughout Australia and New Zealand. The analyses reveal the beetle is invasive in both Western Australia and New Zealand, and is likely closest genetically to mainland Australian populations, rather than Tasmania, but the identical haplotype to the New Zealand incursion was not located. Research in the field and reports from the public and NZDFI have tracked Pst. cloelia (= variicollis) spread through both islands of New Zealand, including now being established in Marlborough and having reach the central North Island plateau. Observations on pest presence in Gisborne are included as a file note.

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