T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Phytophthora pluvialis (Red needle cast)

unranked): SAR
Superphylum: Heterokonta
Class: Oomycetes
Subclass: Incertae sedis
Order: Peronosporales
Family: Pythiaceae
Genus: Phytophthora
Species: P. pluvialis
Binomial name: Phytophthora pluvialis
Common names: Red needle cast, RNC

Phytophthora pluvialis is a new semi-papillate, homothallic fungi that infect the pine species. This fungus-like organism is more closely related to algae than fungi. It is native to the Pacific Northwest in the United States where it affects Douglas-fir trees. This fungal disease turns pine trees red after heavy rain. The needles of pine trees first turn yellow then red and then they fall off the trees a few months after symptoms appear. RNC affects trees of all ages.

In New Zealand, it was first recognised in the winter of 2008 in plantation forests on the eastern coast of the North Island. Phytophthora pluvialis causes RNC on Radiata pine as well as Douglas-fir. In New Zealand, the symptoms start any time between March and September, usually peaking from July onwards. 
Since the small sporangia of Phytophthora pluvialis are carried in airborne water droplets. Wet conditions are necessary to spread this organism. Damp, misty rains are the ideal conditions for this disease to develop.
This disease is now widespread in pine blocks and plantations in the North Island and in pine trees in the northwest of the South Island.

RNC usually attacks trees 10 years or older. It doesn't kill the tree but can temporarily stunt its growth for a year following defoliation. Within three years the tree’s growth will return to normal. There is no damage to the wood so it does not pose a direct threat to New Zealand's log trade. The spores only affect live foliage and do not contaminate logs.

A stand of Pinus radiata trees affected by red needle cast disease. 

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/