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Forest Protection SSIF research on species other than radiata pine 2021/22

By Nicolas Meurisse, Toni Withers, Andrew Pugh, Mike Davy, Darryl Herron, Te Whaeoranga Smallman, Stuart Fraser, August 2022.

Download SWP-T151 (pdf)

Executive summary

Plantation species other than Pinus radiata (radiata pine), such as Douglas-fir, cypresses and eucalypts, continue to be of pivotal importance to ensuring New Zealand has a diversified forest estate resilient against biosecurity threats. As part of the Specialty Wood Products Partnership (SWP), Forest Protection (now the Ecology and Environment research group) contributes with Strategic Science Investment Fund (SSIF) research that is highly responsive to biosecurity threats in the diverse species areas, to ensure sustainable growth of alternative tree species. This report summarises research findings in the last financial year in the aligned projects.

A new polyphagous ambrosia beetle known as GAB, Xylosandrus crassiusculus, has been introduced into New Zealand in 2019. It is native to East Asia and has been a highly successful invader worldwide. Like most invasive ambrosia beetles, X. crassiusculus can attack a wide range of woody plants. Adult females colonize physiologically stressed trees by excavating galleries in which they lay eggs and inoculate a symbiotic fungus, Ambrosiella roeperi. Both the founding female and its larval progeny feed on the fungus, not on the wood. Often the first sign of an attack is the sawdust released by the excavating adult, which takes the form of compacted “noodles” extruding from the tree trunk. Scion completed monitoring in Kumeu using flight intercept traps and wood bolts. Wood bolts not soaked in ethanol received zero attacks. We hypothesize that Eucalyptus trees (among other hardwoods), but only those under stress (emitting ethanol as a stress response), will be under threat of attack from this pest, but may not be as susceptible as other species of woody trees in New Zealand. The manuscript has been submitted to Agricultural and Forest Entomology.

Significant progress has also been made through the Better Border Biosecurity collaboration ( on the safety of insect releases for biological control (through the development of a risk assessment model). Recognition of biosafety risks associated with introduced biocontrol agents (BCAs) is globally increasing, and pre-release assessments of these agents have become more rigorous in many countries, especially New Zealand. We advocate for adoption of a more comprehensive, ecologically- based, probabilistic risk assessment approach to BCA releases. An example is provided using a Bayesian network that can integrate information on probabilities and uncertainties of a BCA to spread and establish in new habitats, interact with non-target species in these habitats, and eventually negatively impact the populations of these non-target species. The new model, BAIPA (for “Biocontrol Adverse Impact Probability Assessment”), could eventually be incorporated into a structured decision-making framework that has potential to support national regulatory authorities such as the EPA (Environmental Protection Authority) in New Zealand. The authors have completed the publication and initiated testing the model with seven additional case studies. The manuscript is now published, but it would violate copyright for a copy to be made freely available on the FGR website. The link is supplied in this report and individuals can obtain copies directly from the author.

Cypress canker disease expression is observed irregularly within New Zealand; however, it tends to be more severe in warmer areas. Because species of Seiridium on Cupressaceae in New Zealand have not been well characterised, there is a lack of knowledge regarding pathogenicity and distribution. Molecular research has continued this year with an additional gene region sequenced. Maximum Likelihood analysis grouped the 47 isolates into four different clades, representing two known species, namely Seiridium cancrinum and C. neocupressi, and two novel clades. Future work should seek to accurately identify the isolates within the NZFS collection and provide pathogenic data. This information will help us understand which are the more important Seiridium species and the threat they pose to cypress and pine in New Zealand. Scion had insufficient resources to complete this research to publication stage.


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