You may be unknowingly spreading disease all over your landscape. Those yellow, brown, or black spots on your tree may be anthracnose. Avoid hosing down your tree to try and clean it, you could be spreading this fungi everywhere!
Over time and repeated attacks, anthracnose can weaken your tree’s health and provide an opportunity for other disease and infestation. Once identified, tree anthracnose should be treated immediately.
toddsmariettatreeservices.com gathered this information to help you identify, treat, prevent anthracnose, and uncover the fungi responsible for causing it.
What Is the Cause of Anthracnose?
Tree anthracnose is caused by a fungal infection fueled by optimal weather conditions. The following are some of the fungi responsible for anthracnose and some of the tree species they infect:
- Apiognomonia Errabunda – Attacks tilia, Quercus, beech, oak, lindens, and Fagus (ficus) trees.
- Apiognomonia Veneta – Attacks london planes and sycamores.
- Colletotrichum Gloeosporioides – Attacks ash, tulip, and cacao or cocoa trees.
- Discula Fraxinea – Attacks maple, ash, and fringetree.
- Glomerella Fungi Species – Attacks banana, mango, papaya, and lemons.
- Gnomonia Fungi Species – Attacks oak, maple, sycamore, walnut, ash, and dogwood trees.
- Marssonina Fungi Species – Attacks aspen, poplars, and cottonwood trees.
- Stegophora ulmea – Attacks elm trees.
The above-mentioned fungi overwinter in either the leaves that have fallen to the ground, or in cankers on the tree’s bark. In springtime, the fungi’s reproduction process is favored by cool temperatures and prolonged periods of rain.
As the fungi generate spores, splashing rain, overhead watering, and/or the wind disperses them to leaf buds, shoots, or young leaves. The fungi then colonize the tissue of the new host and begin producing spores to be carried off in the same manner.
As long as temperatures remain mild and moist conditions persist, the fungi will continue to colonize leaf tissue, produce spores, and reinfect the same leaves or spread to others. Without intervention, this process can repeat itself throughout spring and into early summer.
Anthracnose and other fungal diseases that attack trees need water (moisture) to grow, propagate, and colonize new hosts. These diseases are less common in warmer regions that have less rainfall.
What Are the Symptoms of Anthracnose?
While anthracnose can be caused by several different species of fungi, the symptoms are the same. Here is how to identify an anthracnose infection:
- Bud death
- Twig death
- Dead spots on leaves
- Dead tissue along leaf veins
- Dead blotches between leaf veins
- Unseasonal or premature leaf-drop
- Lesions known as cankers in tree bark (open wounds)
A common symptom among all of the anthracnose diseases is the presence of acervuli. Use a magnifying glass to examine the underside of infected leaves. You are looking for dark colored pimple-like fruiting structures (acervuli).
In infected trees, these structures may also be found peppered along dead twigs.
How Do You Treat Anthracnose?
While damages resulting from anthracnose infections are generally inconsequential to the overall health of a tree, repeated attacks from the disease year after year can weaken a tree’s defenses enough to leave it susceptible to other diseases and insect infestations.
The following measures will help to treat the disease and reduce the potential for infection in the coming springtime:
Don’t Spray the Foliage – Anthracnose fungi depend on splashing water and wind to carry them from one host to another. If you try to wash off the foliage, you are doing more to help the fungi live than to save your tree.
Fallen Leaves – Collect and destroy fallen leaves. These dead leaves (if left on the ground) provide an optimal location for fungi to overwinter.
Pruning – For the fungi and acervuli found in blighted twigs, these areas should be pruned back and destroyed.
Crown thinning will allow more air and light to reach the inner branches and foliage, which in turn will help fight against the fungi.
Depending on the extent of the infection, excessive pruning may be necessary. If this is the case, contact a professional tree service to evaluate the situation.
Tip: To destroy the pruned portion of the tree and/or leaves, light up the fire pit or have a bonfire.
After pruning any diseased plant, shrub, or tree, make certain that your tools are sanitized before storing them or using them again. Use a 1 part bleach to 6 parts water solution to wash your tools.
Fungicides – In areas or with trees that have a history of anthracnose infections, fungicides can be used to further curtail its spreading.
Knowing the species of your tree will help you select the right fungicide. Many of them are labeled for use against specific fungi, and the fungi which cause anthracnose are typically host species specific.
How Can Anthracnose Be Prevented?
By providing plants and trees with well drained and enriched soil, nutrient-rich fertilizer, sufficient water, and annual pruning, you will help them maintain a vigorous defense system and enable them to resist diseases more handily.
If you use a sprinkler or overhead watering system, consider modifying it or replacing it with a drip system. Drip systems don’t create the splashing effect necessary to carry fungus spores from host to host.
Finally, take action against other fungal invaders and pests to prevent the tree’s health from weakening.
Tree Health and Disease Prevention
There is more to preventing tree diseases than just hosing down your trees. To stop the spread of anthracnose and prevent its return, it takes an understanding of what it is and how it spreads from host to host.
In this article, you discovered what causes anthracnose, how to correctly identify it by common characteristics, how to treat it, and the steps to prevent it.
Anthracnose, through repeated attacks, will eventually weaken your tree and allow other more invasive diseases and tree pests to attack. Treatment and prevention measures should begin as soon as this disease is positively identified.
For more signs and symptoms of a troubled tree, visit https://www.toddsmariettatreeservices.com/troubled-tree-signs-symptoms/
Photchana Trakunsukharat, Department of Agriculture, Thailand [CC BY 3.0 au], via Wikimedia Commons