Will Anthracnose Go Away on Its Own?
An Annoyance, Not Usually a Threat
Anthracnose is the common name for a group of fungal pathogens that grow on the leaves and branches of trees of all kinds. While the fungus is unsightly, it isn’t deadly in most cases and usually clears up on its own. Here, we’ll go over how to spot anthracnose, how it affects trees, and what you can do to reduce the chances of it taking hold in the early months of spring.
How to Identify Anthracnose
The fungus group known as anthracnose affects most shade trees and shows up in spring when the weather is cool and moist, with temperatures in the 50s and 60s (Fahrenheit). Anthracnose might not show up every year since it tends to depend on the environmental conditions. The disease is worst in long, wet springs with high amounts of rainfall as flowers and leaves are opening. Young leaves, shoots, and buds are most at risk for infection.
An infected tree will show certain signs of anthracnose, including:
Well-defined black or brown splotches on leaves, flower petals, and branches
Fungal growth along the veins, where moisture is concentrated
Leaves that are shriveled, curled, or cupped
Leaf loss early in the year
A tree is most affected in the lower 10-15 feet of the crown, where moisture most easily builds up. Anthracnose affects a wide variety of trees, including maples and oaks, but dogwoods and sycamore trees are most often affected by the fungus. Most kinds of anthracnose are specialized, with each type only affecting a certain tree. This means anthracnose on a maple isn’t likely to spread to nearby trees of another kind.
While a severe, year-over-year infection of anthracnose on a tree can significantly stress it out through the loss of leaves and the resulting inability to photosynthesize, anthracnose will usually clear up without intervention. If it seems your tree isn’t doing well over spring and is showing signs of anthracnose, checking with a certified arborist is the best way to confirm the infection and set up a management plan to restore your tree to health.
Does Anthracnose Go Away?
In most cases, there isn’t any need to do anything to manage anthracnose on trees. They usually recover from the fungus, which tends to be superficial, only affecting the leaves, petals, and outer branches early in the year. As weather conditions dry up, so will the spread of the fungus. Some trees will self-prune and drop infected leaves and branches, putting out a second round of leaf growth that will be healthier than the first.
Anthracnose, however, will likely return the following spring if conditions are right. The spores survive in dead tissue, and they spread in the air undetected.
How to Treat Anthracnose
Unless it’s a severe infection, we don’t usually need to do anything to treat a tree for anthracnose. A fungicide isn’t necessarily recommended for mature trees, but a severe infection in a young tree (with 50% or more leaf drop) may require a fungicidal anthracnose treatment.
Otherwise, it doesn’t hurt to prune a tree to remove infected leaves and branches. This will help make sure that any spores that remain in dead tissue won’t be present in the coming spring season. A preventative fungicide can be applied to a tree when it seems to have a problem year after year. Connecting with an arborist when your tree is having an ongoing problem with anthracnose will help you understand the best course of action to take for the health of your tree.
How Do You Fight Anthracnose?
Weak, stressed trees are more susceptible to disease and pests, so promoting the health of your trees is the best way to help them defend themselves from an infection. Since anthracnose isn’t a deadly infection, mature, established trees usually don’t require chemical control. There are certain practical steps you can take to help decrease the chance of spreading anthracnose to the trees in your yard, including:
Raking up and disposing of infected leaves (either in the trash or in a hot compost)
Pruning infected branches and twigs to remove dead tissue and any spores
Pruning mature trees regularly to keep them healthy and well-aerated
Avoiding planting trees too closely together
Planting trees in sunny areas where they get lots of ventilation and good drainage
Using mulch around a tree to keep moisture in the ground
Avoiding over-watering trees
Watering trees and grass in the morning rather than at night so that excess moisture can evaporate during the day
For more tree care tips and information on Nashville’s canopy, subscribe to our newsletter! You can also volunteer with us to help keep our neighborhood green cover thriving. If you’d like to plant a tree (or a few!) in your yard this fall, consider purchasing through the Nashville Tree Conservation Corps’ annual tree sale, open from October through March.