Informational table showing disease name, symptoms, pathogen/cause, and management of Poplar diseases. Disease Symptoms Pathogen/Cause Management Cryptodiaporthe canker) At first, a few twigs are killed. The fungus spreads rapidly to cause many variously shaped cankers and kill large branches as it does so. Perennial canker formation leads to leaf yellowing, premature defoliation, and water sprout formation. Green-brown material filled with spores oozes out of the canker during wet weather and dries to a brown color. When the tree walls off the canker, the bark covering the canker may crack, fall away, and thereby expose inner wood to decay fungi. Trees most susceptible are those under drought or other stress. Cryptodiaporthe populea Irrigate to prevent drought stress in the late summer and autumn. Remove infected trees. Cytospora canker Twigs and larger branches die. Brown, circular, sunken cankers form on the bark. During wet weather, yellowish threads of spores ooze out of fruiting structures in the canker. Lombardy poplar is very susceptible. Cytospora Remove infected branches cutting well below the canker. Remove severely infected trees. Rust Small, yellowish-orange areas of powdery spores form on the underside of leaves. These spores spread to the alternate host, hemlock. Melampsora No control is recommended since little damage occurs. Scab and shoot blight Branch tips and young leaves blacken and die rapidly. Olive-green spores of the fungus develop on the surface of dead and dying tissue. Small trees are most susceptible. Venturia tremulae Remove severely infected trees.