This guide covers the basics of several common lawn diseases you might encounter, including their symptoms, underlying causes, and what you can do to manage them effectively.
Brown Patch
- What It Looks Like: Brown Patch is a common lawn disease that often appears during periods of warm, humid weather. You’ll notice circular patches of brown or dead grass, which can range in size from a few inches to several feet. Early in the morning, you might see what looks like a web of purple or grayish-brown threads—this is actually fungal growth. While Kentucky Bluegrass is fairly resistant, grasses like Tall Fescue, Perennial Ryegrass, and Creeping Bentgrass are more susceptible to damage.
- What Causes It: The fungus responsible for Brown Patch, Rhizoctonia, thrives in the thatch layer of your lawn, especially when temperatures soar above 85°F combined with high humidity. The fungus attacks the foliage and crowns of the grass, particularly when the lawn is under stress.
Dollar Spot
- What It Looks Like: Dollar Spot is named for the small, round, straw-colored spots it creates on lawns, which are roughly the size of a silver dollar. Over time, these spots can merge into larger areas of damaged grass. This disease primarily affects cool-season grasses such as Kentucky Bluegrass, Perennial Ryegrass, and Fine Fescue.
- What Causes It: The fungus Sclerotinia homoeocarpa is behind Dollar Spot. It thrives in warm, moist environments and can be spread through contact with contaminated mowing equipment, shoes, or lawn tools.
Fairy Ring
- What It Looks Like: Fairy Ring is easily recognized by the dark green circles or arcs that appear in the lawn during early summer. These rings can vary greatly in size, sometimes growing up to 50 yards in diameter. Mushrooms or toadstools often sprout along the edges of the rings during wet weather.
- What Causes It: Caused by the fungus Marasmius oreades, Fairy Ring feeds on organic matter in the soil, such as dead leaves or tree roots. This fungus grows outward from a central point, weakening or killing grass in its path, which can result in a circular pattern of affected turf.
Leaf Blight
- What It Looks Like: Leaf Blight typically affects cool-season grasses like Kentucky Bluegrass, Tall Fescue, and Perennial Ryegrass. The disease causes water-soaked lesions on grass blades that eventually turn yellow or brown. In severe cases, large areas of the lawn can appear bleached or dead.
- What Causes It: Leaf Blight is often triggered by mowing the lawn in the evening followed by heavy watering at night. The fungus responsible for this disease thrives in warm, humid conditions and can spread via mowing equipment, watering tools, or foot traffic.
Gray Leaf Spot
- What It Looks Like: Gray Leaf Spot primarily affects warm-season grasses like Bermuda, Zoysia, St. Augustine, and Tall Fescue. The disease creates tan-colored lesions with brown or purplish borders on the grass blades. As it progresses, large areas of the lawn may turn brown and die.
- What Causes It: The fungus Pyricularia grisea causes Gray Leaf Spot. It thrives in warm, humid climates and can cause extensive damage if not controlled promptly.
Leaf Spot
- What It Looks Like: Leaf Spot disease, often grouped with Melting Out, creates small, circular or elongated spots on the grass blades. These spots are usually brown or tan with reddish borders, and as the disease worsens, the grass can turn yellow or brown and die.
- What Causes It: Leaf Spot is often caused by a pathogen that becomes particularly destructive during the heat of summer, leading to significant damage if not managed effectively.
Melting Out
- What It Looks Like: Melting Out presents similar symptoms to Leaf Spot, with discolored spots on grass blades. As the disease progresses, it attacks the base and roots of the grass, leading to yellow, thinning patches and dead grass.
- What Causes It: This disease is caused by a fungus that becomes active during cool, wet weather and can cause severe damage if left untreated.
Necrotic Ring Spot
- What It Looks Like: Necrotic Ring Spot is characterized by circular patches of dead grass with a brownish-yellow ring surrounding a healthier center, sometimes referred to as “Frog Eye.” These rings can vary in size but are generally about a foot in diameter.
- What Causes It: The fungus that causes Necrotic Ring Spot is most active during cool weather, but symptoms can appear throughout the growing season, especially during hot, dry summer months when the grass is under stress.
Powdery Mildew
- What It Looks Like: Powdery Mildew appears as a white or grayish powdery coating on the leaves and stems of grass, causing the affected areas to become stunted and weakened. This disease is most common on cool-season grasses like Annual Bluegrass, Bentgrass, and Fescues.
- What Causes It: Powdery Mildew thrives in cool, humid conditions, particularly in shaded areas with poor air circulation. It is most active during the spring and fall.
Pythium Blight
- What It Looks Like: Pythium Blight can cause grass to turn brown and die rapidly, often within a few hours. The disease leaves a greasy, water-soaked appearance on the grass, sometimes accompanied by a foul odor. It is common on poorly drained soils.
- What Causes It: Pythium Blight is caused by a fungus that thrives in warm, wet weather. The disease can spread quickly, particularly on lawns with high nitrogen levels or poor drainage.
Controlling Lawn Diseases A thick, healthy lawn is the best defense against lawn diseases. While changes in temperature and weather often reduce the spread of diseases, you can also improve your lawn’s health by adjusting your care practices. Avoid watering or mowing when diseases are active, and ensure your mower blades are sharp to minimize damage. Regular fertilization, aeration, and proper lawn maintenance can help prevent diseases and promote a stronger, more resilient lawn.
If you suspect your lawn is suffering from any of these diseases, contact Green Seasons Professional Lawn Services for a thorough diagnosis and customized treatment plan to restore your lawn’s health and beauty.