The threat of myrtle rust to New Zealand and how science is contributing to our preparedness - Beccy Ganley - nzppi

The threat of myrtle rust to
New Zealand and how science is
contributing to our preparedness.
           Beccy Ganley

What is myrtle rust?

▪ Rust disease – Austropuccinia psidii                                   Myrtle rust
▪ Can affect foliage, flowers and fruits
▪ Wide and expanding host range - over 445 known host species
▪ Wind-dispersed over long distances
▪ Spores can be transported on cars, clothing and personal effects

         Acknowledge Angus Carnegie (NSW Department of Primary Industries) for photos

Guava rust                  Eucalyptus rust                Ohia rust

Cryptic symptoms

A. psidii across the Pacific
                                              2005

                    2013
           2010
                           Raoul Is.   2017

Climate suitability

                                                       ▪ Variety of different models
                                                       ▪ Modelled to Austropuccinia psidii
                                                         species complex

                                                       ➢ All predict suitability of areas in NZ

                                                       ▪ Models have not been completed
                                                         for the strain of A. psidii in the
                                                         Pacific
http://www.fs.fed.us/rm/pubs_other/rmrs_2012_hanna_j
001.pdf

Host susceptibility
▪ Infects in excess of 445 species in 73 genera worldwide.
▪ All myrtaceous genera considered potentially susceptible.
▪ Species vary in their susceptibility to different pathogen
  strains
▪ Evidence of variation in susceptibility within a species.
▪ Most susceptible hosts include:
Agonis flexuosa (willow myrtle), Chamelaucium uncinatum
(Geraldton wax), Decaspermum humile (silky myrtle),
Eugenia reinwardtiana (Cedar Bay cherry), Gossia inophloia
(thready-barked myrtle), Melaleuca quinquenervia (paper
bark tea tree), Rhodamnia angustifolia, R. maideniana, R.
rubescens (scrub turpentine), Rhodomyrtus psidioides
(native guava) and Syzygium jambos (rose apple).

Risk to New Zealand natives
Almost 30 native myrtaceous species
▪ Kunzea
▪ Leptospermum
▪ Lophomyrtus
▪ Metrosideros
▪ Neomyrtus
▪ Syzygium

   ➢ Several species known to be susceptible
   ➢ Degree of susceptibility unknown

Control of myrtle rust
▪   Prevent spread
▪   Destruction of infected material
▪   Chemical control
▪   Host resistance

                          Unsprayed    Sprayed

How science is contributing to our preparedness

Myrtaceae barcoding project

▪ MPI-funded; completed by Matt Buys and Beccy Ganley, Scion
MPI recognised various difficulties with plant identification during an
incursion:
    • wide variety of Myrtaceae species in NZ
    • difficult to distinguish some species
    • lack of structures for identification
    • number of plants to identify/extent of incursion

Barcode database of Myrtaceae in NZ
▪ 104 species of Myrtaceae
   • covers the range of species in NZ
   • includes species of economic and cultural importance
▪ Sequenced ITS, ETS and matK regions
▪ Rapid and accurate identification method
   • only a small amount of plant material needed.

Host susceptibility – expat plant survey

▪ Scion-B3 funded; completed by Peter Scott and Elizabeth Miller, Scion

   ‘Expatriate survey of native NZ Myrtaceae planted throughout
  Australia to determine their susceptibility to Puccinia psidii and
                       improve management’

▪ Focused on Botanic Gardens, Private Gardens, Research Institutes
  and Nurseries in Brisbane, Sydney and Melbourne, Australia.
▪ NZ native Myrtaceae found to be susceptible to P. psidii included
  Metrosideros excelsa, M. kermadecensis, Lophomyrtus obcordata and
  L. x ralphii

Metrosideros kermadecensis, Sydney          Lophomyrtus obcordata,Victoria

                   Lophomyrtus. x ralphii, Victoria

Host susceptibility – Masters student

▪ Peter Scott, Beccy Ganley, Elizabeth Miller (Scion), Mike Wingfield,
  Jolanda Roux (FABI), Carlos Rodas (Colombia), Rebecca Stanley
  (Auckland Botanical Gardens), Amanda Black and Nick Waipara (Māori
  Biosecurity Network)
      ‘Identifying myrtle rust resistance in key NZ Myrtaceae’
▪ Determine susceptibility of 5 keystone Myrtaceae species to the two
  main Austropuccinia psidii (myrtle rust) isolates
    • Pacific/Australian strain
    • South African strain
    Capability development in biology, epidemiology and
    control of myrtle rust disease

Biosecurity networks interventions
▪ Biological Heritage National Science Challenge
  funded; Philip Hulme (LU), Daniel Stouffer
  (UoC), Beccy Ganley (Scion), Nick Waipara
  (AC), plus others
▪ Develop network models that link the potential
  for pest or pathogen spread through
    • Nursery pathways
    • Natural areas
▪ Models will allow stakeholders to identify
  opportunities for interventions to either contain
  or slow the rate of spread of unwanted
  pathogens,
▪ Provide new methods to safeguard New
  Zealand’s native flora and ecosystems.

Future Research
▪ MBIE Catalyst Fund Proposal – PFR (lead), Scion & Australian
  colleagues
    • Host susceptibility
    • Seed banking
    • UAV surveillance
▪ Better Border Biosecurity (B3) meeting in May to identify biosecurity
  research priorities