Frequently Asked Questions

Could didymo spread to lakes throughout New Zealand?

Yes. Although didymo prefers a river environment with clear water flowing over stable substrate at depths sufficient for light penetration to drive photosynthesis, blooms have been found in South Island Lakes. Lake Wakatipu, for example, contains visible didymo on some parts of the lake shore.

What is pandemic human influenza?

All influenza viruses are unstable and constantly changing. New human influenza viruses emerge every year.

Human pandemic viruses are very rare but occur when a new virus, to which humans have no immunity, emerges. Genetic studies have shown that some human pandemic influenza viruses have been derived from avian influenza viruses.

How do I manage Tuber brumale?

If you don't have T. brumale: You should source seedlings that have been tested and certified as being free from T. brumale.

If you do have T. brumale: Many truffle growers are familiar with mycorrhizal species such as Scleroderma sp. and Tuber maculatum which compete with more valuable truffle species. The skills needed to manage T. brumale are similar and T. brumale has the advantage of being a marketable edible species.

What other areas of the world has didymo been found?

Didymo's native distribution is limited to cool temperate regions of the Northern Hemisphere, including the rivers of northern forests and alpine regions of Europe, Asia and parts of North America. Prior to its arrival in New Zealand didymo was not found in the Southern Hemisphere. Over the past twenty years, the distribution of didymo appears to be gradually expanding outside its native range and it is now also found in South America (Chile). Furthermore, even within its native range, there have been reports of excessive growths in areas where it previously existed only in low concentrations. 

Why is it taking so long to wipe it out?

Wiping out a pest like the painted apple moth takes time. It took three years to wipe out the white spotted tussock moth after it was discovered in Auckland in 1996. MAF has taken a less aggressive approach to the painted apple moth because it spreads more slowly and it was worth trying alternatives to aerial spraying first. Even so, MAF has successfully contained the painted apple moth to western Auckland and is on track to wipe it out.

What is European Foulbrood?

European Foulbrood is a bacterial disease of bees caused by Melissococcus pluton. It is not present in New Zealand, but is found in many other beekeeping countries. European Foulbrood does not form spores, but can be spread on bee products and beekeeping equipment. European Foulbrood is often considered internationally as a ‘stress’ disease - a disease that is usually not fatal to a colony unless the colony is already under stress for other reasons. Healthy colonies usually survive European Foulbrood. Overseas, outbreaks are controlled chemically by feeding antibiotics to infected colonies.

When does the 1m separation of potatoes for Taiwan in storage start?

We have checked the Taiwan requirements. These state that the potatoes must be segregated in storage. We have therefore removed the word “packed” from section and now say to “segregate potatoes for Taiwan from others in the storage facility”. we have also reduced the segregation distance to 100mm.

Are there any avian influenza viruses in New Zealand?

Over 5000 samples have been taken from wild birds (migrating and resident species) in New Zealand since 1976. A small number of low pathogenic notifiable avian influenza viruses (H5 or H7 subtypes) have been found in healthy mallard ducks.

How can I find out if I have Tuber brumale?

It is possible for a skilled mycologist to identify T. Brumale mycorrhizae on root samples using a microscope, and DNA testing can be used to confirm its presence. The NZTA is investigating options to help growers establish if they have T. brumale in their truffières.

Is Gum leaf skeletoniser dangerous?

The gum leaf skeletoniser caterpillar is covered with protective spines that sting and may cause irritation. The stiff spines are hollow and contain venom, which can be injected into the human skin upon contact. This often results in local pain (sometimes severe) and welts (swollen patches on the skin) that tend to become itchy. The reaction to gum leaf skeletoniser may last for many days. Note that the spines of dead caterpillars or on shed skin retain their ability to sting.

In case of reaction to gum leaf skeletoniser caterpillars, the following first aid is advisable:

  1. Apply ice packs to the exposed area.
  2. In case of eye contact, wash area thoroughly and seek medical attention.
  3. If ingestion of caterpillar occurs, seek medical attention immediately.
  4. If symptoms develop beyond the immediate area of the sting (e.g. widespread rash, shortness of breath or collapse) call an ambulance straight away.

Biosecurity NZ has prepared fact sheets providing more specific public health information:

For further information, see Derraik JGB. 2006. Erucism in New Zealand: exposure to gum leaf skeletoniser (Uraba lugens) caterpillars in the differential diagnosis of contact dermatitis in the Auckland region. New Zealand Medical Journal 119 (1241) (offsite link to