Diseases
The introduction of exotic invasive tree pathogens to North America has resulted in large scale tree mortality and the replacement of once dominant native tree species. Sudden Oak Death, Laurel Wilt, White Pine Blister Rust, Chestnut Blight, Butternut Canker, and Dutch Elm Disease, all serve as grim reminders of successful establishment of invasives that have significantly altered our urban and forest landscapes.
Below are the top five diseases that impact Missouri trees.
Diseases/Pathogens
Butternut, also called white walnut, nuts are an important food source for wildlife. When butternut develops a canker, an oblong-shaped abscess that oozes, the wounds eventually cut off the trees nutrient supply and it dies.
For more information:
Chestnut blight is caused by Cryphonectria parasitica. The blight fungus causes cankers, dieback and ultimately death of the aboveground portions of the tree. The first sign of the disease is cankers.
For more information:
- APHIS ( HTML)
Oak wilt is caused by Ceratocystis fagacearum. White oak is more resistant to oak wilt than red or bur oak, but can still be killed if infected. American, Chinese, and European chestnuts, tanbark oak, and bush chinquapin are also susceptible. Susceptible trees will die within a few weeks of infection, while trees with some resistance will decline slowly for two to three years.
Signs of infection include leaf tips turning brown, wilting and falling off while still green. The die-off progresses down the tree, twigs and branches will die off. A fungal mat develops under the bark, sap-feeding and bark beetles will feed on the fungal mat and spread spores to other trees.
For more information:
HRD is most damaging in plantation-grown conifers (especially pine and spruce) where stumps of trees that were cut down offer a place for infection to start. Once a stump is infected, HRD spreads to other living trees through root contact underground.
For more information:
- Wisconsin Department of Natural Resources ( HTML)
A phenomenon known as Sudden Oak Death was first reported in 1995 in central coastal California. Since then, tens of thousands of tanoaks (Lithocarpus densiflorus), coast live oaks (Quercus agrifolia), and California black On these hosts, the fungus causes a bleeding canker on the stem.
The pathogen also infects Rhododendron spp., huckleberry (Vaccinium ovatum), bay laurel (Umbellularia californica), madrone (Arbutus menziesii), bigleaf maple (Acer macrophyllum), manzanita (Arctostaphylos manzanita), and California buckeye (Aesculus californica). On these hosts the fungus causes leaf spot and twig dieback.