 | | Diplodia Tip Blight |  | | Dogwood Anthracnose |  | | Dogwood Anthracnose |  | | Ash Anthracnose |  | | Maple Anthracnose |  | | Oak Anthracnose |  | | Sycamore Anthracnose |
|  Additional Information | | | |
The Leaf Blight
Wet weather conditions often allow leaf diseases to infect tree leaves in the spring. The most common group of fungal leaf blights are the
anthracnose diseases. Several species of trees are affected by an anthracnose disease, each one caused by a separate and specific fungus. So, while oak, maple, sycamore, ash, and
dogwood trees are commonly affected by an anthracnose disease, each one is caused by a different fungus.
Each disease has unique symptoms, but generally the leaves will develop brown or black spots and blotches. Leaves will often drop from the trees as the disease develops during extended periods of wet weather. These leaf blights do not usually significantly harm the tree. Sycamore anthracnose may be slightly more serious, since it can also infect twigs when conditions are favorable for the disease. Dogwood anthracnose can be fatal when trees are infected for several years because twigs and even larger branches are often infected.
Austrian pine is also affected by a common needle disease called diplodia tip blight. This disease is not in the anthracnose group, however, wet conditions also allow this disease to infect newly expanding needles causing them to be stunted and discolored. Chronic fungal infections on the tree may result in dead branches and poor tree vigor.
Dogwood Anthracnose
Dogwood anthracnose was first reported in the mid-1970s in New York. The origin of the disease in not known although most pathologists believe it is not native. This anthracnose fungus is now present throughout much of the the range of flowering dogwood. Pacific dogwood in the northwestern United States and British Columbia is also infected. The states of the Northeastern Area where infection has been confirmed are New Hampshire, Massachusetts, Rhode Island, Connecticut, New York, New Jersey, Pennsylvania, Maryland, West Virginia, Ohio, and District of Columbia.
Weather and conditions of the growing site contribute to the severity of the disease. The causal agent of dogwood anthracnose is a fungus that prefers cool, moist conditions. Trees in wooded areas are more likely to be infected, particularly at higher elevations or along waterways. Dogwoods of all ages and sizes are susceptible, and after initial infection, trees can die within 2 to 5 years depending upon the site. Symptoms appear first in the lower crown affecting leaves and twigs. Tan spots with purple rims occur on the leaves in spring and there may be twig dieback and epicormic branching. Cankers develop on twigs, branches, and trunk as the disease progresses.
The flowering dogwood has tremendous economic value as an ornamental tree. Nurseries became concerned as sales plummeted after media reports that dogwoods were doomed. In response, they launched a public relations campaign and supported numerous research efforts. Their message is that well-maintained landscape trees are far less vulnerable to the disease than woodland trees.
Research has shown that care and cultural practices are critical to the health of dogwood and its resistance to the disease. Trees do much better in sunny areas with good air circulation and good drainage. Sufficient water, nutrients, and absence of mechanical injury also contribute significantly to tree health.
Pruning of epicormic sprouts and raking of dead, fallen leaves helps eliminate fungal spores that spread the disease. Future research is needed to address more precisely the conditions that contribute to health. It is not known how spores infect the trees or why certain native trees show some resistance. Despite heavy losses to the dogwood resource, it appears that the flowering dogwood will continue to be a part of our eastern forests and landscapes.
Butternut Canker
Butternut canker is causing decline and mortality throughout the butternut’s Ohio range. In an attempt to protect the remaining resource and its potential genetic resistance to the disease, the Ohio Department of Natural Resources Division of Forestry developed and implemented a butternut management policy in 1994. The policy requires retention of healthy butternut trees on State forest lands. The policy also encourages education of private woodland owners regarding proper health assessment and management of this threatened species. The USDA Forests service has a factsheet on Butternut Decline.
Guignardia Leaf Blotch
High moisture levels during the spring and early summer of 1996 encouraged the development of Guignardia leaf blotch on Ohio buckeye. This fungal leaf disease produces brownish-red foliage and leaf drop each year on Ohio buckeye, yellow buckeye, and horse chestnut trees. Disease levels were heavier than usual in 1996 due to weather conditions favorable for infection. The disease develops after most of the annual growth of the host plant is complete, so overall health effects are minimal. Ohio buckeye trees subjected to excessive heat show symptoms similar to Guignardia leaf blotch.