Expat plant communities useful biosecurity sentinels

Adventurous kiwis on their OE have been known to get into the odd spot of bother over the years. So too can our expatriate plant communities. Their problems are not with local constabulary, but with local pests and diseases. By monitoring communities of New Zealand native plants in overseas situations – especially in climates similar to our own – we gain a valuable insight into how they might be affected by foreign organisms that have so far been kept out of our country (see also Biosecurity 68:20, 15 June 2006).

In 2002, the National Research Council recommended that plants native to the United States growing in other countries' botanic gardens and arboretums be monitored to help predict which non-native species could present risks if they arrived in the United States. To our knowledge, New Zealand is the only country evaluating this 'expatriate plant communities' concept to see if it can add value to pre-border risk analyses.

The project aims to:

  • identify where New Zealand plants are growing overseas
  • determine which overseas localities are most climatically matched to New Zealand
  • develop protocols for collecting long-term monitoring data
  • interpret data on potential pest and disease threats.

Up to 20 staff from Crop & Food Research, AgResearch and Scion are contributing to this project, which will be reviewed in June 2008 by its potential end users, MAF Biosecurity New Zealand (MAFBNZ) and the Department of Conservation.

Overseas, New Zealand native plantings have historically been for plant conservation purposes. Utilising existing botanical garden conservation networks and the internet, the project team has communicated with the guardians of more than 107 overseas New Zealand plant collections in 13 countries (see Table 1). Curators at each garden were surveyed on the extent of their New Zealand planting, a species list, climate and soil type, history of pest and disease problems and a range of other details. Information was collated and entered into a newly constructed database intended for future phases of this project and for other biosecurity and conservation initiatives.

To best target future monitoring and response efforts, climate matching was used to identify regions of the world where temperatures and climatic conditions closely match those typically experienced by native plants growing in New Zealand. New Zealand host plants growing in similar conditions overseas could harbour future pests and diseases. The most suitable sites were situated in Australia, north-eastern Europe and parts of western USA (Figure 1).

Another task undertaken by the project team was developing a standard survey and sampling protocol for the long-term monitoring of these overseas plant collections. Entomologists and plant pathologists developed a symptom-based field protocol designed for use by non-experts. The protocol includes how to collect samples, deliver samples to overseas diagnostic collaborators or import non-viable materials into New Zealand for identification.

Twelve overseas botanic gardens have been visited since the project began two years ago. Gardens in the United Kingdom (Kew gardens, Ventnor gardens), Canada (UBC gardens), United States (Hawaii), Australia (Hobart, Melbourne, Adelaide) and New Zealand (Christchurch gardens) were visited on an ad hoc basis to help develop and trial the protocols. A number of damaged or diseased New Zealand plant species were identified using the symptom-based protocol. The pests or diseases were then confirmed as not being present in New Zealand using organism records collected by MAFBNZ and the Department of Conservation as well as the new Plant-SyNZ database (Biosecurity 78:25, 15 September 2007), which will help determine their risk to New Zealand natural ecosystems.

Information collected from overseas visits is entered into the Expatriate Plant Communities Database, which will allow searches to be made on the basis of plant species, region, pest or pathogen. The internet-linked database also allows photographs of damage symptoms to be submitted to assist with preliminary diagnoses or identifications.

Now that the conceptual phase of the project is nearing completion, it is anticipated that the second phase of a full-scale monitoring trial for pests or diseases in the selected New Zealand overseas gardens will proceed. Potential methods to achieve long-term monitoring data to increase MAFBNZ's pre-border readiness and response may include New Zealand biosecurity researchers travelling overseas to conduct surveys, or by reciprocal monitoring projects with overseas collaborators. Regardless, informal inspections of overseas plantings by MAFBNZ staff while attending other business will assist in the compilation of expatriate plant community data.


Anon 2002. Predicting invasions of nonindigenous plants and plant pests – Committee on the Scientific Basis for Predicting the Invasive Potential of Nonindigenous Plants and Plant Pests in the United States. Washington D.C., National Academy Press.

Oates M 1999. New Zealand Plants and Their Story. In: Oates M ed. New Zealand plants and their story.

To access Plant-SNZ database:

Table 1

Figure 1
Figure 1: Expatriate plant communities (red dots) where New Zealand plant collections are located compared with the climate match index (CMI) indicating the location’s climatic similarity to New Zealand growing conditions (CMI of 0.9–1.0 is the best match to New Zealand conditions).

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Page last updated: 18 June 2008