| Disease |
Symptoms |
Pathogen/Cause |
Management |
| Crytodiaporthe Canker |
At first, a few twigs are killed. The fungus
spreads rapidly to cause many variously shaped cankers, killing
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. |
