112 U.S. DEPT. OF AGRICULTURE MISC. PUB. 939 



P. coulteri Don 



P. halepensis Mill. 



P. jeffreyi Grev. & Balf . 



P. latifolia Sarg. 



P. nigra poiretiana (Ant.) Aschers. & Graebn. 



P. muHcata Don 



P. pinaster Ait. 



P. pinea L. 



P. ponder osa var. scopulorum Engelm. 



P. radiata Don 



P. sdbiniana Dougl. 



P. sylvestris L. 



P. thunbergii Pari. 

 Literature : 



Siggers, P. V. The brown spot needle blight of pine seedlings. 



U.S. Dept. Agr. Tech. Bui. 870 : 1-36. 1944. 

 Wolf, F. A., and Barbour, W. J. Brown-spot needle disease of 

 pine. Phytopathology 31 : 61-74. 1941. 



Septoria Canker of Poplars 



J. E. Bier 



Department of Biology and Botany, University of British Columbia, 

 Vancouver, British Columbia 



Septoria musiva Pk. (Perfect Stage — Mycosphaerella populorum 

 G. E. Thompson) is a leaf disease and perennial stem canker of exotic 

 and hybrid poplars in North and South America. The first leaf 

 lesions appear from 3 to 4 weeks after the opening of the buds, 

 mostly confined to leaves on the lower branches. Later the infection 

 becomes general throughout the trees. The fungus produces necrotic 

 spots of various shapes and sizes which often coalesce to involve large 

 areas of the leaf. The individual lesions are brown with yellowish 

 to white centers, and small black pycnidia develop throughout the 

 lesions on both leaf surfaces. Under moist conditions the conidia are 

 discharged from the pycnidia as curled, pinkish cirri. The conidia 

 are hyaline, continuous to four (mostly two) septate, measuring from 

 17 to 57/x long. 



The canker stage originates in the bark of twigs of the current year, 

 entering the host through mechanical wounds, lenticels, stipules, or 

 leaf petioles. By early summer a very conspicuous symptom is the 

 presence of one or more dead leaves on the leaders, at the ring scars, 

 or on the axillary branches produced on 2-year-old stems. At the bases 

 of the dead leaves cankered bark is evident, which is usually black, 

 frequently enclosing yellowish to white areas in which the pycnidia 

 mav be found. 



The cankers may girdle and kill the leader and axillary branches 

 during the first year and later spread from the axillary branches into 

 the main stems. On entering the main stem the pathogen may produce 

 a perennial canker resulting: in considerable malformation of the main 

 stem. Isolations from the diseased bark at the margin of older cankers 

 frequently produce cultures of Cytospora chrysosverma (Pers.) Fr., 

 and it is possible that advanced cankers mav result from a combined 

 attack of Septoria and other fungi such as Cytospora. 







