Dothistroma needle blight
Symptoms, identifying factors, spread and treatment for Dothistroma needle blight (DNB).
- 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 flush of needles around December or January.
- Disease development continues through to winter – when it slows but does not stop.
- Peak disease occurs about September.
- Affects pines from planting age up to about 15 years.
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 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.
Plan your copper fungicides spraying for early summer for any trees with less than 15% of the crown affected (at the time of assessment during winter).
Farm Forestry New Zealand has further information on DNB, including pictures and links to the latest research.