Red needle cast
Symptoms, identifying factors, spread and treatment for Red needle cast (RNC).
- 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.
RNC is abundant in parts of the Waikata, 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.
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 does not recommend spraying affected trees until at least 35% of the tree's leaves show signs of infecton. This percentage can vary – more valuable trees should, in general, be treated more promptly.
Farm Forestry New Zealand has further information on RNC, including pictures and links to the latest research.