Dothistroma needle blight

Dothistroma pini

This fungus kills pine needles and affects pine tree growth. The disease could cost our forestry industry millions of dollars each year.

About dothistroma needle blight (DNB)

DNB lives only on pine needles. DNB is caused by a more than one fungus species. One species, Dothistroma septosprum, is found all over the world, including New Zealand. Dothistroma pini also causes DNB, but it is not present in New Zealand.

D. pini is found mostly in north-central United States. It has also been found in Ukraine, Russia, France, and Hungary.

Global distribution of D. pini

World map showing distribution of Dothistroma pini

Why this is a problem for New Zealand

There are many unknowns about what D. pini could do in our unique environment. We don't know:

  • what pine species it would most likely affect
  • how it would interact with D. septosprum.

Hopefully these are questions we'll never have to answer.

We do know D. pini causes DNB. DNB kills the needles, reducing the growth of the tree. Serious infections can kill a pine tree. The wood of the tree becomes denser, making it harder to process.

The disease could cost the forestry industry millions of dollars each year in crop losses and disease control.

How it could get here

The fungus could get here on pine nursery stock or pine needles. Biosecurity New Zealand has strict measures in place to reduce the chance of pine diseases like DNB getting through the border.

How to identify DNB

Pine needles with brown discolouration
Close up of pine needles infected with DNB.
Image: CC 2.0 US Department of Agriculture

Needles:

  • turn red-brown – there is a clear distinction between the red zone and the remainder of the needle
  • remain rigid and are not easily removed from branches
  • remain on the tree after they have died.

The lower half of the crown is usually affected. In severe cases, the entire crown can turn red-brown.

Other identifying factors

  • Symptoms start on the new flush of needles around December or January.
  • Disease development continues through to winter – when it slows but doesn't stop.
  • Peak disease occurs about September.
  • Affects pines from planting age up to about 15 years.

Tell us if you find it

If you're a forester and you find similar symptoms:

  • photograph it
  • don't touch it as you could spread the fungus
  • call 0800 80 99 66
  • ensure you follow good biosecurity procedures to prevent the spread of disease.

Note: This information is a summary of this disease's global distribution and potential impacts on New Zealand. 

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