Abstract: The poplar canker caused by Phomopsis sp. is a new disease occurring on poplars in China. Two shapes of conidia are found. One is fusiform, hyaline, single-cell, 1.64—2.74×9.59—13.70μm, and another is linear with curved top, 1.37—1.78×15.00—27.40μm. The suitable growth temperature of fungus is 25-32℃, its suitable pHis 6—10, and potato dextrose agar, malt agar media and bean cake are suitable for its growth. The disease occurs in the last ten days of April, conidia matures in the second and last ten days of May, and the dispersing peak of conidia is in the second and last ten days of June. Experiments with poplar cuttings treated by carhendazim, thiopanate methyl and asomate (200-fold concentration) are carried out in laboratory. The results show that the harm of fungicides is produced on cuttings in30,60 and 90 minutes, but, a concentration of 100—200-fold is harmless in10 minutes and shows a good effectiveness for controlling the disease. An effect of 87.5% is obtained on young trees in afforested plantation when the above mentioned fungicides (100-fold) concentration are used.

Key words: Poplar, Canker disease, Phomopsis sp., Poplar cutting, Control, wheat, lodging resistance, lignin., lodging index, hemicelluloses