Poplar trees are fast-growing deciduous trees that are often used in landscaping and are also grown for their wood. While poplar trees are generally free from pests, sometimes cankers can occur on the trunk and limbs of the a tree. Caused by an infection, the canker is unsightly and can threaten the health of the tree if left untreated.
Signs and Symptoms
A canker is a sunken area in the bark on the trunk or branches of a tree. It is caused by a pathogen of some kind attacking the soft tissues beneath the bark. Cankers vary from being barely visible to a noticeable round, sunken area on the tree that may appear yellow, brown or black. Eventually, the bark will split open and the sore can ooze sap. Small fruiting bodies of the fungi may also be visible as tiny pimple-like protrusions. If left untreated, the infection can eventually girdle the affected part of the tree, killing branches or the tree itself.
Means of Infection
Different pathogens cause cankers in different species of trees. Cankers that attack poplars are caused by fungi. The spores of the fungi are most often dispersed by wind or rain and will enter the tree through wounds. Some pathogens can infect the tree through the leaves. Occasionally, pruning tools, insects or animals can also be infected and can transmit the disease.
Known pathogens of poplar trees includes the fingi Cytospora chrysosperma and Leucocytospora nivea, which attack all poplars but are more prone to attack more susceptible varieties, such as Carolina, Silverleaf and Lombardy poplars. Lombardy poplars are also affected by Crytodiaporthe populea fungus, although it has been seen on other poplars, as well. White poplar can become infected with Hypoxylon mammatum.
No known pesticides are effective against a canker infection. To treat an infected tree, the diseased area must be pruned out, including the bark and any underlying tissues. The cut should be made all the way down to healthy wood. If the main trunk is infected, there is no pruning that will be effective and the tree should be removed to prevent infecting other trees nearby.
Increasing the strength of poplar trees through good horticultural practices is important. Maintaining the tree's health with regular watering, fertilizing and pruning can increase the tree's ability to defend itself from infection. Sanitizing tools that may come in contact with trees after each cut is also recommended. Reducing the level of pests may also help to lessen the risk of cankers forming. Development and planting of disease-resistant varieties of poplar can also help.