Phytophthora pluvialis is causing a new disease on Pinus radiata in New Zealand
In 2013, Phytophthora pluvialis was described as a new species from isolates which had been collected from streams, soil and canopy drip in mixed tanoak-Douglas fir forests (Notholithocarpus densiflorus - Pseudotsuga menziesii) in Curry county, Southwestern Oregon (US), as well as from two additional streams in other areas of Western Oregon (EPPO RS 2015/169). Further studies conducted in Oregon have detected P. pluvialis in the foliage of P. menziesii but associated with mild symptoms only.
In 2014, P. pluvialis was reported to be the cause of red needle cast on Pinus radiata in New Zealand. This new disease is characterized by discrete olive-coloured bands on needles, and these lesions are frequently accompanied by small, dark, resinous spots or narrow bands. The lower part or the entire crown of affected trees turn reddish brown, and is followed by premature needle cast. In New Zealand, these symptoms were first noticed during winter 2008 in forest stands on the Eastern coast of the North Island. Subsequent monitoring surveys showed that symptoms usually started in late autumn to late winter, but that newly developing spring and summer foliage was seldom affected. It was also observed that both disease incidence and severity varied among areas and years. The presence of P. pluvialis was consistently found in diseased P. radiata samples. It is noted that on rare occasions, P. kernoviae was also recovered from needles presenting the same symptoms. Although no direct tree mortality could be attributed to P. pluvialis in New Zealand, it was considered that control strategies (e.g. chemical control and breeding programmes) should be developed and implemented to minimize the impact of red needle cast disease in P. radiata plantations.
Sources
Dick MA, Willimas NM, Bader MKF, Gardner JF, Bulman LS (2014) Pathogenicity of Phytophthora pluvialis to Pinus radiata and its relation with red needle cast disease in New Zealand. New Zealand Journal of Forestry Science 44(6), 12 pp. http://nzjforestryscience.springeropen.com/articles/10.1186/s40490-014-0006-7
Ganley RJ, Williams NM, Rolando CA, hood IA, Dungey HS, Beets PN, Bulman LS (2014) Management of red needle cast, caused by Phytophthora pluvialis, a new disease of radiata pine in New Zealand. New Zealand Plant Protection 67, 48-53.
Hansen EM (2015) Phytophthora species emerging as pathogens of forest trees. Current Forestry Reports 1, 16-24.
Hansen EM, Reeser P, Sutton W, Gardner J, Williams N (2015) First report of Phytophthora pluvialis causing needle loss and shoot dieback on Douglas-fir in Oregon and New Zealand. Plant Disease 99(5), p 727.
Reeser P, Sutton W, Hansen E (2013) Phytophthora pluvialis, a new species from mixed tanoak-Douglas-fir forests of western Oregon, U.S.A. North American Fungi 8(7), 1-8.