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

Dothistroma septosporum (Red band needle blight)

Kingdom: Fungi
Division: Ascomycota
Subdivision: Pezizomycotina
Class: Dothideomycetes
Order: Capnodiales
Family: Mycosphaerellaceae
Genus: Dothistroma
Species: D. septosporum
Binomial name: Dothistroma septosporum
Synonyms: Dothistroma pini. Eruptio pini, Mycosphaerella pini
Common names: Red band needle blight, Needle blight

Dothistroma septosporum is a fungal disease that affects the needles of conifers. 
Dothistroma needle blight was first observed near Tokoroa in 1962.  Over 60 species have been reported to be prone to infection (list below).
The first signs of infection can be seen are yellow and brown spots that develop on the living green needles. These develop into brick-red bands in midsummer, resulting in the death of needles and defoliation. There is a clear division between infected and uninfected regions. The infection starts on the base of the crown on older needles, which then turn a brownish red at the tip, while the rest of the needle continues to remain green. Small black spots (fruit bodies) develop in the red infected bands, these erupt spilling our spores. Mortality as a result of Dothistroma needle blight alone is extremely rare.

Life Cycle
Spread initially in moist conditions, the pathogen requires physical transport either through mist and rain or by direct contact with other infected needles. Once the needles have been exposed and the fungus germinates, the pathogen then penetrates the needle through the stoma. The ideal germination temperature is 12-18C, with high levels of humidity. The needles will then begin to show signs of infection, and eventually, the pathogen produces stromata, which is the pathogen's fruiting body. These are formed in the spring and early summer and usually coincide with above-average levels of rainfall. From these, the blight is then passed on to the following year's growth. The stromata can be seen as a clear or white mass exuding from red spots on the leaf.

Over 60 species have been reported to be prone to infection.
SCION the website of New Zealand Farm Forestry Association list the following host susceptibility list has been developed based on observations and field trials.

Very Highly Susceptible: Pinus attenuata
Highly Susceptible: Pinus nigra subsp. laricio, P. ponderosa (in the central North Island), P. jeffreyi, P. radiata (variable resistance after 15 years of age, depending on climate).
Moderately Susceptible: Pinus pinaster, P. canariensis, P. lambertiana, P. muricata blue strain (variable, but usually more resistant than P. radiata and exhibits resistance with age probably earlier than P. radiata).
Slightly Susceptible: Pinus contorta, P. elliottii, P. hartwegii, P. monticola, P. nigra subsp. nigra.
Slightly Susceptible: (usually infected only when growing near other highly infected species) Larix decidua, Picea omorika, Picea sitchensis, Pseudotsuga menziesii.
Very Slightly Susceptible: Pinus ayacahuite, P. coulteri, P. michoacana, P. montezumae, P. patula, P. pseudostrobus, P. sabiniana, P. serotina, P. strobus, P. sylvestris, P. taeda, P. torreyana.

Dothistroma septosporum(red band needle blight) on Pinus radiata, showing infection of both young and old foliage.
Courtesy: H.C. Evans, CABI Wallingford (GB).

Attack of Dothistroma septosporum on Pinus mugo over several years showing only last years needles (paintbrush-looking).

Symptoms of Dothistroma septosporum: on the needles of Pinus mugo.

Yellow spots and necrotic bands on needles of Pinus mugo caused by Dothistroma septosporum

Symptoms of Dothistroma septosporum: needles with brown necrotic tissue, showing fruit bodies breaking through the epidermis by longitudinal slits, raising a flap of the epidermis.

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