Pine needle diseases

There are 4 main pine needle diseases in New Zealand. Find out what the diseases are and how to recognise and treat them.

Blight in Radiata pine

Blight is a type of plant disease commonly caused by fungi. There are different sorts of fungi that can cause blight, including mildews, rusts and smuts.

If your pine trees look like they may be suffering from blight, check the table to narrow down the likely cause.

 

Cyclaneusma needle cast

Physiological needle blight

Red needle cast Dothistroma needle blight
When
September to November June to November April to October All year
Tree age
6 to 20 years 15 years + Usually 3 years + Planting to 15 years
Spread

No pattern

Very severe

Small area affected

More than 50% of trees within the affected area

Small to medium-sized area affected

Almost all trees within affected area

Widespread

Almost all trees within affected area

Wide variation between trees

Needles

Yellow

Gold

Brown

Brown

Red-brown

Grey

Olive (with or without black bands)

Yellow

Red

Olive (with or without black bands)

Brown

Grey

Red bands with black spots

Wilt
None Only at later stages None Slight
Retention
Needles detach easily Needles are retained Needles detach easily Needles are retained but die
Cambium & bark

No damage

No lesions

No resin

No damage

No lesions

No resin

No damage

No lesions

Some resin blobs may appear at base of affected trees

No damage

No lesions

No resin

If you're unsure what may be affecting your forest, NZ Farm Forestry has a step-by-step identification guide that may help.

Detailed disease descriptions

The 4 main diseases present in New Zealand differ from each other in a number of small but important ways.

Expand All
Cyclaneusma needle cast (CNC)

Symptoms

Needles:

  • turn mottled yellow then brown
  • often develop transverse (horizontal) bands during the later stages of disease development.
  • remain rigid and are very easily removed from branches.

After the needles are cast, the tree crown appears very thin.

Other identifying factors

  • The entire tree crown may be affected.
  • Disease is not uniform in a stand unless the trees are genetically identical – affected trees are scattered amongst unaffected trees.
  • Symptoms start September or October, with a second (usually less severe) cast occurring around April.
  • Trees aged between 6 and 20 years are most affected.

Spread

CNC is abundant in the Waikato and Taranaki regions and very common in Northland and on the east coasts of both the North and South islands.

It is uncommon in Otago and the greater Wellington-Wairarapa region.

No areas in New Zealand are known to be free of CNC.

Treatment

No treatment is believed to be economically viable.

Physiological needle blight (PNB)

Symptoms

Needle colouring:

  • In the initial stages, needles have distinct olive or olive-with-black resinous bands.
  • In later stages, needles turn red-brown.
  • After one year, needles turn grey.

Needles droop and wilt and are not easily removed from branches.

Other identifying factors

  • Symptoms develop on foliage that flushed in the previous year.
  • The entire tree crown may be affected.
  • On affected branches, nearly all foliage shows symptoms.
  • Symptoms start between May and November.
  • Disease peaks between October and November.
  • Trees older than 14 years are most affected.

Spread

PNB is abundant in parts of the Waikato region and very common in Northland and on the east coast of the North Island.

It is uncommon in the greater Auckland region, Taranaki, the greater Wellington-Wairarapa region and all but the west coast of the South Island.

PNB is known to be absent in the areas surrounding the Abel Tasman National Park.

Treatment

Phosphite spray may be effective in treating PNB. Research is still being done to work out how much phosphite should be used and how frequently it should be applied.

Scion doesn't recommend spraying affected trees until at least 35% of the tree's leaves show signs of infection. This percentage can vary – more valuable trees should, in general, be treated more promptly.

Red needle cast (RNC)

Symptoms

Needle colouring:

  • In initial stages, needles have distinct olive or olive-with-black resinous bands.
  • In later stages, needles turn yellow then red-brown.

Needles remain rigid but are easily removed from branches.

Other identifying factors

  • The entire tree crown may be affected.
  • Symptoms may start anytime between March and September but are rare during summer.
  • Peak disease occurs from July to September, depending on the region.
  • Needles are cast or blown off the branch within a few months of symptoms. After the needles are cast, the tree crown appears very thin.
  • Affects trees of all ages.

Spread

RNC is abundant in parts of the Waikato, Central Plateau and Gisborne regions and is very common in Northland, the upper South Island and the Bay of Plenty.

It is uncommon in the greater Auckland region, Taranaki, the greater Wellington-Wairarapa region, Hawkes Bay and the area surrounding Abel Tasman National Park.

PNB is known to be absent in most of the South Island.

Treatment

Phosphite spray may be effective in treating RNC. Research is still being done to work out how much phosphite should be used and how frequently it should be applied.

Scion doesn't recommend spraying affected trees until at least 35% of the tree's leaves show signs of infection. This percentage can vary – more valuable trees should, in general, be treated more promptly.

Dothistroma needle blight (DNB)

Symptoms

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 branch
  • 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.

Spread

DNB is abundant in parts of the Waikato and Central Plateau regions and is very common in the Bay of Plenty and upper South Island.

It is uncommon in the greater Auckland region, Taranaki, the greater Wellington-Wairarapa region, Hawkes Bay and the area surrounding Abel Tasman National Park.

No areas in New Zealand are known to be free of DNB.

Treatment

Plan your copper fungicide spraying for early summer for any trees with less than 15% of the crown affected (at the time of assessment during winter).

Find out more

Who to contact

If you have questions about the information on this page, email info@mpi.govt.nz

Last reviewed: