If the green leaves in your landscape are turning brown (and winter is far from the horizon), then your plants may be suffering from anthracnose. The reality of a fungal disease taking over your landscape isn’t comforting, but with the right control measures put in place, you can help restore your yard’s greenery.
Anthracnose can affect many plants in the yard, including flowers, fruits, vegetables, grass, shrubs, and trees. In this anthracnose guide, we’ll focus on how anthracnose affects your turfgrass and beloved trees.
- What is anthracnose?
- Anthracnose in your lawn
- Anthracnose in your trees
- Who has the time for fungus?
What is anthracnose?
Anthracnose is a general term that describes related fungal diseases that typically cause dark lesions on plant leaves, including trees, shrubs, and turfgrass. Anthracnose also can attack fruits, flowers, and vegetables.
A single fungus doesn’t cause anthracnose. Many different types of fungi cause anthracnose, including Colletotrichum sp., Kabatiella sp., and Apiognomonia sp.
Anthracnose in your lawn
Types of grass affected by anthracnose
Annual bluegrass and creeping bentgrass are the most vulnerable turfgrasses. Other grasses that anthracnose can infect are:
- Kentucky bluegrass
- Perennial ryegrass
- Fine-leaf fescues
- Tall fescue
How to identify anthracnose in the lawn
The fungus that causes anthracnose disease in turfgrass is called Colletotrichum cereale (formerly Colletotrichum graminicola).
Anthracnose symptoms may appear as foliar blight or basal rot. Foliar blight is limited to the leaves and causes the leaves to appear yellow to reddish-brown. Basal rot is more destructive than foliar blight and causes the leaf sheaths, stolons, and crowns to darken and rot.
Key anthracnose symptoms to look out for include:
- Yellowish or reddish patches of grass that may fade to brown
- Elongated, reddish-brown lesions with yellow halos developing on the grass leaves
- Black, pad-like structures on the infected leaves and sheaths –– these structures are called acervuli, and they have protruding black spines. You can see the acervuli with a small microscope or magnifying glass.
- Crown tissue may appear water-soaked and black.
What causes anthracnose in the lawn?
A pathogen requires two things: A host (your grass) and the right environmental conditions.
The weather and how well you maintain the lawn have a significant role in developing a pathogen’s desirable conditions. Anthracnose thrives in yards that are stressed from poor maintenance. If you haven’t been showing your lawn some love, then your yellowing grass may be in the grips of anthracnose.
Here are some factors that can cause anthracnose in the lawn:
- Cool temperatures in early spring
- Warm temperatures and high humidity in summer
- Long periods of leaf wetness
- Poor drainage
- Thatch buildup
- Excessive traffic
- Low mowing heights
- Compact soil
- Low or unbalanced fertility
Pro Tip: If you don’t treat anthracnose right away, it may spread to other areas of your lawn. Remember those small black structures we mentioned earlier, called acervuli? They produce spores that infect healthy grass tissue. The spores are spread most often by splashing rain and mowing equipment.
How to get rid of anthracnose in the lawn
When something weird starts growing in our lawn, our first instinct is to spray the affected area with harsh chemicals. After all, that’s how many of us get rid of the mildew and mold growing in our bathrooms. Shouldn’t the same technique work in our rotting yards?
Although fungicides can help cure some lawn diseases, fungicides are more effective against anthracnose when used as a preventative treatment. In other words, you’ll have more success against anthracnose when using the fungicide to prevent the disease rather than cure it.
So how can you cure anthracnose without fungicide? Well, you’ll need to reverse what made your lawn so appealing to the disease in the first place. Were you watering the turf in the evenings instead of the morning? Have you not been aerating the soil? The key to removing anthracnose is to modify your lawn care routine.
When anthracnose is growing in your yard, here are some curative measures you can take:
- Correct your fertilization regime. If your lawn doesn’t get enough nutrients, it may struggle to grow healthy turf. Performing a soil test is the best way to determine what nutrients your lawn needs.
- Relieve your lawn’s compacted soil with an aerator. Compacted soil limits the root system’s access to water, nutrients, and oxygen.
- Remove excessive thatch. A thick thatch layer in the lawn can harbor fungi.
- Raise your mowing height. Scalping the lawn and mowing too low is stressful for your turf.
- Water early in the morning (before 10 a.m.) instead of in the evening. If you water in the evening, the water will cling to the grass and create a moist environment for fungi.
- Use fungicide as a last resort. If the disease continues to spread despite the maintenance adjustments you are making, the Clemson Cooperative Extension recommends applying a fungicide containing propiconazole or azoxystrobin with propiconazole. Always use chemicals according to the product label directions.
How to prevent anthracnose (and other diseases) in the lawn
If you don’t want anthracnose and other fungi to infect your turf, you’ll need to prevent the desirable conditions for their growth. For anthracnose, that means eliminating wet leaves, compact soil, or nutrient-deficient soil.
If anthracnose or another lawn disease continues to return to your lawn, it may prove helpful to combine cultural measures with a preventative fungicide treatment. When spraying these chemicals on the lawn, reading and following the product’s instructions is always essential. Instructions will provide the best application method, how much to apply, and what time of year to spray the solution.
But remember, you don’t want to rely solely on preventative fungicides. When you incorporate the following lawn care treatments into your maintenance routine, you’ll boost your lawn’s health and make it more resilient against disease:
- Remove leaves and other plant debris from the lawn. Leaves make excellent real estate for fungi that are looking to overwinter in the yard.
- Mow the grass regularly (and correctly). Adjust your mowing height so that you’re not mowing so low that you scalp the lawn. And remember to mow regularly, because grass that’s too tall is very inviting to pests and disease. Finally, never cut more than ⅓ of the grass blade at a time; otherwise, you’ll stress the turf.
- Leave behind grass clippings. When your grass is infected with a fungal disease, you don’t want to leave grass clippings on the lawn (otherwise, the disease will spread). But when you’re mowing healthy turf, leaving the grass clippings behind gives your lawn a nutritional boost.
- Water the lawn the right way. Watering the lawn less often and for long periods promotes a healthy root system. Watering the lawn too often and for short periods encourages a weak root system. Secondly, the best time to water the grass is in the early morning, before 10 a.m.
- Invest in a sprinkler system. Watering the lawn is a chore you can’t skip. An automatic sprinkler system takes the burden off your shoulders and creates a watering schedule that meets your lawn’s specific moisture needs.
- Plant grass seed that’s disease-resistant and suitable for your lawn. To achieve a healthy lawn, you must grow grass that is suited for the local climate. For example, if you live somewhere with long, boiling summers and short, mild winters, you’ll want to grow warm-season grass instead of cool-season grass. When planting grass seed, consider planting a variety that’s resistant to common diseases.
- Test your soil. Testing your soil allows you to determine what nutrients your turf is missing and how you can make the appropriate amendments.
- Fertilize your grass. Many lawns will struggle to remain healthy if the soil lacks nutrients. After you take a soil test, develop a fertilizing schedule for your turf.
- Aerate compacted soil. Aeration relieves compacted soil by creating small holes in the ground. This treatment allows water, oxygen, and nutrients access to your turf’s roots.
- Remove thatch that exceeds ½-inch thick. Thatch is the dead organic matter that accumulates between the soil and the grass. Too much thatch can create the perfect environment for fungus.
- Overseed the lawn. Does your lawn keep thinning year after year? The trick is to plant new grass seed before that lawn begins to thin. Routine overseeding encourages a dense, thick lawn.
- Remove existing weeds. Weeds don’t grow with your lawn’s health in mind. They compete with your grass for nutrients, space, light, and moisture. If a weed invasion becomes severe, it may weaken your turf. Remove existing weeds by hand-pulling them or applying a post-emergent herbicide.
- Apply pre-emergent herbicide. Pre-emergent herbicides help prevent new weeds from growing in the yard. They are not an ideal solution for weeds that already exist.
- Control grubs and other pests. Grubs live just underneath the soil’s surface. As they munch on the lawn’s root system, the turf begins to weaken.
- Spread a ½-inch layer of compost across the lawn. Compost acts as organic fertilizer by adding nutrients to the soil. You can spread a compost top dressing with a rake or brew a compost tea to spray on the lawn.
What other grass diseases can infect my lawn?
It would be a lift-off your lawn’s shoulders if anthracnose were the only grass disease you needed to worry about. But several lawn diseases can infect your turf, which is why it’s so important to keep your lawn healthy. Various lawn diseases can be a pain in the yard, including:
- Brown patch
- Dollar spot
- Fairy ring
- Gray snow mold
- Leaf spot and melting-out
- Pink snow mold
- Powdery mildew
- Red thread
- Summer patch
Anthracnose in your trees
Types of trees affected by anthracnose
In general, anthracnose does not kill trees (it’s mostly a cosmetic issue). However, if defoliation, branch dieback, or cankering occurs for several years, the tree will weaken and become susceptible to other problems, such as insects and other diseases.
Trees that are susceptible to anthracnose include:
How to identify anthracnose in trees
Tree leaves infected with anthracnose develop dark lesions similar to those on grass blades and other plants. Here are the symptoms to look for if you think your tree may have anthracnose:
- Small dead spots develop on the leaves
- Dead leaf margins
- Dead leaf tips
- Dead areas along leaf veins
- Leaves fall prematurely
- Twig death
- Infected twigs and the underside of infected leaves have small, fungal fruiting structures (you may need the help of a magnifying glass or microscope to see them)
- The lower and inner leaves and branches show the most severe symptoms
- Cankers develop on twigs, branches, and the trunk; cankers often appear as sunken lesions
- Cankers cause girdling and dieback by restricting the flow of water and nutrients
- The tree is defoliated from the ground up, leaving undamaged foliage at the top of the tree
What causes anthracnose in trees?
If you never felt inclined to remove leaves from the yard, you certainly will now! Raking leaves can be back-aching work, but doing the job can save your favorite trees from losing their beauty. Why? Because anthracnose pathogens overwinter in infected leaves and twigs.
In spring, the overwintering anthracnose fungi produce microscopic spores that spread via irrigation water, splashing rain, and wind to young tree buds. The spores then germinate under cool, moist weather conditions and infect leaf tissue. If favorable conditions persist, a new generation of spores develops in the leaf tissue and is spread via splashing rain to create new infections in the host.
How to manage anthracnose in trees
Once symptoms begin to develop in your tree, it becomes challenging to control anthracnose. But don’t let this information deter you from saving your tree. Here are some measures you can take to help prevent reinfection, reduce the disease, and protect other trees:
- Rake and dispose of (or burn) fallen leaves and twigs during autumn and the growing season.
- Prune infected trees in the winter to increase air circulation and remove diseased twigs and branches.
- Destroy or dispose of disease twigs and branches after pruning.
- Do not irrigate near infected leaves. Avoid sprinkler systems that wet the leaves.
- When planting new trees, choose cultivars that are resistant to anthracnose. Plant the trees far enough apart to maximize air circulation and sunlight (this helps leaves dry faster).
- Keep trees healthy by watering and fertilizing adequately. You can determine what fertilizer your tree needs by conducting a soil test. Stressed trees are more susceptible to anthracnose infection.
- Apply preventative fungicide in the spring, just before buds break. You’ll likely need to make multiple applications to ensure disease resistance. Always refer to labeled instructions for when to apply the fungicides and how often. The University of Arkansas Division of Agriculture recommends fungicides containing chlorothalonil, thiophanate-methyl, or propiconazole for many landscape trees.
What other diseases can infect my trees?
Anthracnose-causing fungi aren’t the only pathogens that can infect your trees. If your tree is wilting, has powdery leaves, or develops cankers, it may be battling a disease. Common tree diseases include:
- Cytospora canker
- Hypoxylon canker
- Phytophthora bleeding canker
- Phytophthora root rot
- Powdery mildew
- Shot hole
- Sooty mold
- Thousand cankers disease
- Verticillium wilt
Who has the time for fungus?
Mowing the lawn, fertilizing the grass, spraying fungicides –– who has time for all that? Preventing fungal disease and encouraging healthy grass and trees is no piece of cake.
Hire a local lawn care professional or tree care specialist to treat your landscape’s existing anthracnose disease and to prevent future fungal growth from occurring. If your busy schedule only allows a few hours of free time, why spend that time sweating over fungus when you can ask for professional help?
Main Photo Credit: Scot Nelson | Flickr | public domain