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Mycosphaerella dearnessii

EPPO code

SCIRAC

Anamorph

Lecanosticta acicola (syn. Lecanosticta pini)

Synonym

Scirrhia acicola

Common names

English names: Brown spot needle blight
Nordic names: Brunpletnålefald hos fyr (DK)
Estonian name: Pruunvöötaud

Major host plants

The most important hosts in Europe are: P. contorta, P. halepensis, P. muricata, P. palustris, P. pinaster, P. pinea, P. radiata, P. strobus, P. sylvestris and P. taeda. However, P. banksiana is highly resistant.

Symptoms

Symptoms appear on the needle as small (3 mm), yellow, resin-soaked spots, which later become dark-brown with a prominent yellowish-orange border. As the disease develops, these spots enlarge and girdle the needle. Infected needles present three distinct zones: dead tips, central areas with spots in green tissue, and green bases. Round black spots of fruiting bodies can be seen in the dead parts of the needles. When pines are heavily attacked, the whole needle turns brown and falls prematurely. In less severe attacks, needle fall may be delayed for one or two years. Successive years of severe disease may result in the death of the branch or the entire tree. Disease can affect trees of any age but seedlings are most susceptible.

Mycophaerella dearnessii. Courtesy of EPPO - D Jurc, Forestry Institute, Ljubljana (SI)

See more pictures on EPPO´s website

Distribution

Mycosphaerella dearnessii appears to originate in America and has spread from there to other continents including the EPPO Region.

A map can be downloaded from EPPO's website. See instructions here.

Biology

Conidia are produced during moist periods and spread each spring to susceptible hosts. The spores grow on the needle surface and penetrate via stomata into the needle. The period for infection is from spring to late summer. The period from inoculation to display of symptoms and mature fruiting bodies varies with temperature, time of year and species of pine; from about 1-2 months on young foliage to 4-7 months on old foliage. Ascospores are formed and mature 2-3 months after infected needle tissue die. Both spore forms overwinter in dead and infected needle tissue.

Major pathway(s)

Conidia can be carried short distances by rain splashes or by insects and on forestry equipment. Airborne ascospores may play an important role in long-distance dispersal of the pathogen. Most likely is long-distance spread through movement of infected nursery stock and in seed contaminated with needle debris.

Detection and inspection

An indication of the presence of M. dearnessii in pine needles is the appearance of yellow, occasionally resin-soaked spots which later become brown with the prominent yellowish border. The macroscopic symptoms at the beginning of disease development can easily be confused with those due to M. pini (red band needle blight) or M. gibsonii if no reddening is visible. Laboratory examination is required for positive identification.

Pest status and importance

In Europe, although M. dearnessii is only established on a few sites and usually spreads slowly, eradication efforts have only been partly successful to date. The fungus kills the foliage and retards the growth of many pine species. Attack over several years can kill the trees.

Source of information

See further information here:

Author: Christiane Scheel
Editor: Dorthe Vestergaard

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