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 does Gum leaf skeletoniser look like?

Gum leaf skeletoniser goes through four different life stages, each looking very different from the other:

Gum Leaf Skeletoniser Moth

  • Eggs are about 1 mm in diameter and are laid in groups of 100 to 200 in parallel rows on young leaves. The eggs are yellow-green at first and turn brown as they develop.
  • Caterpillars are hairy and coloured pale yellow with black and grey markings. Older caterpillars have a distinctive 'hat' on their heads.
  • Cocoons are usually formed under bark or in leaf litter and are rarely seen.
  • Moths are dull grey with silver-grey forewings and a wingspan of 20-30mm.

Two gum leaf skeletoniser life cycles are completed each year, one in summer and one in winter. For more information on the biology of this insect, see the Uraba lugens Factsheet Link to PDF document (181 KB).

Are there plans for a didymo eradication programme?

No, there are no plans to eradicate. Past experience with invasive species indicates that eradication of didymo is unlikely. No country has ever attempted to control or eradicate didymo. In New Zealand, a range of management options have been investigated including control, reducing the spread, minimising impacts and protecting high value sites. We are mindful that any control action must not create more environmental problems than it might solve. Advocating Check, Clean, Dry cleaning procedures to waterway users is used to prevent the further spread and establishment of didymo and other freshwater pests.

Who nominates when the PCN soil survey is undertaken and how do they do this?

The grower decides what surveys are needed. We have now updated the registration form to allow the grower to nominate the type of survey required for each production being registered.

Is New Zealand free from echinococcus/hydatosis?

New Zealand has not had any case of Echinococcosis/hydatidosis since 2000. Under the Biosecurity (Declaration of a Controlled Area) Notice – Echinococcus granulosus (Hydatids) it states raw offal from livestock shall not be accessible by dogs:

i. Slaughter and dressing of livestock shall take place in a dog-proof enclosure.
ii. Owners shall control their dogs at all times in such a manner as to prevent them from having access to raw offal of livestock.
iii. Offal shall be cooked by boiling for a minimum of 30 minutes before feeding to dogs.

Further information is found here: Link to PDF document

This is not to be confused with sheep measles (Taenia ovis or Cysticerious ovis) which is present in New Zealand. Further information is found on this link: (offsite link to

Does varroa harm humans or livestock?


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.

How do I develop my Operating manual?

Operating manual templates will be made available on the MAFBNZ website. They provide a basis only for the development of your operating manual, because it must be specific to your facility. The Operator training course also provides information and help with development of an operating manual.

How does avian influenza spread to humans?

Human cases of the H5N1 strain have been caught mainly by people in very close and prolonged contact with poultry in places such as markets and poultry farms, where there is a high density of different species of bird mixing, and where they are exposed to both live and dead birds and their droppings.

New Zealand does not have similar poultry rearing and marketing environments and there is little risk of people in New Zealand being infected through normal contact with birds.

What are the chances that GM corn has cross-pollinated with other corn?

There is no cross-pollination risk because the crops have only just germinated.