Common Lawn Diseases and How To Treat Them
Common Lawn Diseases and How to Treat Them
A lush, green lawn is a source of pride for homeowners, but sometimes, despite your best efforts, lawn diseases can strike. This can be frustrating, and humbling as you try and identify and treat these areas of concern. And don't worry, this can happen to anyone! Most likely it's not your fault, but you can control how you take care of it, and if you're here, you clearly care about your outdoor green space, and are already on the right path to keeping it healthy.
Early diagnosis and treatment of these diseases is crucial to maintaining a healthy lawn. Here’s a guide to some common lawn diseases and how to effectively manage them:
(Please note: I recommend herbicides and fungicides many times throughout this article, but I will always recommend cultural practices first that you can try. I always try and limit the amount of chemicals I use on green spaces, and only recommend if it is absolutely necessary.)
Table of Contents:
Brown Patch
Dollar Spot
Powdery Mildew
Fairy Ring
Red Thread
Rust
Pythium Blight
Anthracnose
Leaf Spot
Slime mold
1. Brown Patch
Symptoms: Circular patches of brown, dead grass surrounded by a dark ring.
Cause: Brown patch thrives in warm, humid conditions, often exacerbated by overwatering or excessive nitrogen fertilization.
Treatment: Improve air circulation by pruning nearby trees or shrubs. Avoid watering in the evening, as wet grass overnight can promote fungal growth. Apply a fungicide labeled for brown patch according to manufacturer instructions.
2. Dollar Spot
Symptoms: Small, round, straw-colored patches that can grow and merge into larger areas. This common disease can affect even the most manicured lawn, so don't worry if you see this in your yard.
Cause: Dollar spot thrives in warm, humid conditions with low nitrogen levels and often occurs during periods of drought or excessive moisture.
Treatment: Increase nitrogen levels through fertilization, but avoid excess nitrogen in late summer. Water deeply and infrequently to promote healthy root growth. Apply a fungicide specifically designed for dollar spot if outbreaks occur.
3. Powdery Mildew
Symptoms: White, powdery fungal growth on the surface of leaves and stems, often in shady areas with poor air circulation.
Cause: Powdery mildew thrives in cool, humid conditions and can spread rapidly in overcrowded or poorly ventilated lawns.
Treatment: Prune overhanging branches to improve air circulation. Water in the morning to allow foliage to dry during the day. Apply a fungicide labeled for powdery mildew if cultural practices alone are insufficient.
4. Fairy Ring
Symptoms: Rings or arcs of dark green, fast-growing grass often accompanied by mushrooms or toadstools.
Cause: I remember when my daughters were little, these 'fairy rings' would elicit wild imaginings of magical happenings going on in our yard through the night. A circle of mushrooms magically grown by fairies to encircle their frivolities and dancing! And if you choose to believe this (no judgments here!) you can stop reading this section now. For everyone else, feel free to read on.
Fairy rings are caused by soil-inhabiting fungi that break down organic matter, leading to nitrogen accumulation or depletion.
Treatment: Aerate compacted soil to improve drainage and reduce fungal activity. Fertilize and water the affected area to promote uniform grass growth. Remove mushrooms promptly to prevent spore spread.
(A quick safety note: There over 10 000 different kinds of mushrooms, and many of them are poisonous. Never ingest a mushroom unless you are 100% sure of it's identification.)
5. Red Thread
Symptoms: Pinkish-red threads or webs visible on grass blades, which later turn brown and die.
Cause: Red thread thrives in cool, moist conditions and is often associated with nitrogen-deficient lawns.
Treatment: Improve nitrogen levels through fertilization, particularly with slow-release nitrogen sources. Avoid excessive nitrogen in late summer to prevent disease recurrence. Water deeply and infrequently to promote healthy grass growth.
6. Rust
Symptoms: Orange or yellowish-brown dust-like spores on grass blades, giving the lawn a rusty appearance.
Cause: Rust thrives in dry, low-nitrogen conditions and spreads rapidly during warm, humid weather.
Treatment: Improve nitrogen levels through fertilization, but avoid excess nitrogen in late summer. Increase mowing frequency to remove infected grass blades. Apply fungicides if rust outbreaks are severe and cultural practices alone are ineffective.
7. Pythium Blight
Symptoms: Irregularly shaped patches of water-soaked, slimy, or greasy-looking grass that quickly turn brown and die. Pythium blight can look very similar to other grass diseases
Cause: Pythium blight thrives in hot, humid conditions with excessive moisture, often exacerbated by overwatering or poor drainage.
Treatment: Improve soil drainage and avoid overwatering. Water in the early morning to allow grass to dry during the day. Avoid mowing wet grass to prevent disease spread. Apply fungicides labeled for pythium blight if outbreaks occur.
8. Anthracnose
Symptoms: Irregularly shaped patches of sunken, water-soaked, or yellowing grass that can develop into large dead areas. This is also a common fungal disease of shade trees that results in leaf spots, cupping or curling of the leaves as well as early leaf drop.
Cause: Anthracnose thrives in hot, humid conditions and can be exacerbated by poor soil drainage or excessive thatch buildup.
Treatment: Improve air circulation and reduce thatch through aeration. Avoid overfertilization with quick-release nitrogen sources. Apply fungicides labeled for anthracnose if cultural practices alone are insufficient. Anthracnose is generally not a significant threat to the health of the plant and often does not require treatment.
9. Leaf Spot
Symptoms: Small, dark-colored spots on grass blades or plant leaves that can merge and cause extensive damage.
Cause: Leaf spot thrives in cool, wet conditions and can spread rapidly in overcrowded lawns or areas with poor air circulation.
Treatment: Improve air circulation and reduce thatch through aeration. Avoid overhead watering and water in the early morning to allow grass to dry. Apply fungicides labeled for leaf spot if outbreaks occur despite cultural practices.
It's important to note that once a plant is infected the contaminated areas won't respond to treatment, so prevention is very important and is a more effective treatment. Affected foliage should be removed at the first sign of the bacteria or fungus, making sure to remove the whole infected leaf. Of course this is harder with grass. In this case just treat the infection and mow as usual.
Bacterial vs Fungal: Bacterial leaf spots typically have a more angular appearance that the fungal leaf spots.The spots tend to be bound between the veins, while the fungal leaf spots will cross the veins. This is because the bacteria is inside the plant and cannot cross the vein easily, while the fungal leaf spots grow on the surface and can then cross the veins easily. Knowing how to identify this will assist you in knowing the proper way to treat the infection.
10. Slime Mold
Symptoms: Gelatinous or powdery gray, yellow or white fungal growth on grass blades that can appear overnight.
Cause: Slime mold is typically harmless to grass and thrives in cool, moist conditions with organic matter present.
Treatment: Slime mold usually disappears on its own within a few days. If aesthetic concerns arise, gently rake the affected area to break up the mold and promote drying.
Conclusion
Maintaining a healthy lawn involves proactive management of common lawn diseases. I know from experience that at times, it can be frustrating to see your lawn suffer when you put effort into having the best lawn on the street. By implementing proper cultural practices, such as good watering habits, adequate fertilization, and improving soil conditions, you can minimize the risk of lawn diseases and ensure your grass remains green and vibrant throughout the growing season. Regular inspection and prompt treatment of any disease symptoms are key to preserving the beauty and health of your lawn, allowing it to be an oasis for your family all throughout the warm weather months.
