Identifying & Preventing Fusarium Blight
Fusarium blight is a particularly destructive lawn disease that can cause extensive damage to your grass. Unlike some fungal infections that primarily affect the grass blades, Fusarium blight can attack both the foliage and root system, leading to significant thinning and even permanent loss of turf.
To help our readers preserve their lawns and combat this damaging lawn disease, we have put together this guide to identifying and preventing Fusarium blight on your property!
What Does Fusarium Blight Look Like?
Fusarium blight often starts as small, circular patches of wilting or dead grass that are typically 2 to 6 inches in diameter. These patches may initially appear sunken, with the grass taking on a reddish-brown, straw-colored, or light tan hue. Over time, the affected areas can expand, sometimes forming irregularly shaped patches up to 2 feet wide.
One of the most recognizable characteristics of Fusarium blight is the development of "frog-eye" patterns. In these cases, the center of the dead patch may recover slightly, leaving behind a ring of dead grass surrounding a patch of still-living turf. The distinct pattern is often a strong indicator of Fusarium blight, though other diseases, such as necrotic ring spot, can sometimes create similar symptoms.
Grass affected by Fusarium blight often appears dry and brittle, as if suffering from drought stress. However, watering the lawn does not revive the affected areas, which is a key difference between Fusarium blight and simple moisture stress. Upon closer inspection, you may notice darkened, rotting roots and crowns, which indicate that the fungus has infiltrated the lower parts of the plant, cutting off essential nutrients and water.
Key Characteristics:
- Circular or irregular patches of dead or dying grass (1–2 feet wide)
- Straw-colored or reddish-brown grass in affected areas
- Dark, water-soaked lesions on grass blades
- "Frog-eye" pattern featuring dead center with a green halo
- Thin, wilted, or matted turf in humid conditions
Conditions That Cause Fusarium Blight
Fusarium blight is caused by fungi in the Fusarium genus, with Fusarium culmorum and Fusarium roseum being the most common culprits in lawn infections. This disease thrives in hot, dry weather, particularly when daytime temperatures exceed 85°F and nighttime temperatures remain above 70°F. The combination of high heat and moisture stress weakens turfgrass, making it more susceptible to fungal attack.
Extended periods of drought or improper irrigation practices, such as shallow and frequent watering, create an ideal environment for Fusarium blight to develop. Lawns that experience excessive foot traffic or soil compaction are also at greater risk, as poor soil structure can hinder water absorption and weaken the root system.
- AVOID EXCESS THATCH! A thick thatch layer (over ½ inch) provides an ideal breeding ground for fungal spores while also preventing water and nutrients from reaching the roots effectively. Maintaining a healthy thatch layer is key to preventing Fusarium blight.
Grass Types Affected By Fusarium Blight
Fusarium blight primarily affects cool-season grasses in cooler climate regions. While warm-season grasses like Bermudagrass and Zoysiagrass are generally more resistant, they are not completely immune, especially if the lawn is already weakened by environmental stress or improper maintenance. The most commonly affected grasses include:
- Kentucky Bluegrass: One of the most vulnerable grass types to Fusarium blight, particularly in hot and dry conditions.
- Perennial Ryegrass: Susceptible, though typically not as severe as in Kentucky bluegrass.
- Fine Fescues: Can develop Fusarium blight, especially when stressed by drought or poor soil conditions.
- Tall Fescue: Less commonly affected but may still develop symptoms in extreme conditions.
How Does Fusarium Blight Spread?
Fusarium blight spreads primarily through fungal spores, which can be carried by wind, water, lawn equipment, and even foot traffic. The fungus can persist in the soil and thatch layer for long periods, even when symptoms are not visible. Fusarium blight is often considered a type of snow mold, and its web-like mycelium will creep along and infect grass blades.
The disease often becomes active when conditions favor fungal growth, such as hot, dry weather followed by high humidity. Spores can germinate rapidly in moist environments, especially when dew or irrigation keeps the grass wet for extended periods. This is why overwatering, particularly in the evening, can exacerbate Fusarium blight rather than alleviate it.
Lawns with poor drainage or compacted soil are more susceptible because they trap moisture at the surface while preventing deep root growth. The combination of shallow roots and fungal infection leads to rapid turf decline, allowing the disease to spread even more quickly.
Will Fusarium Blight Kill Your Grass?
Fusarium blight can cause severe damage, but whether it kills your grass depends on the extent of the infection and the health of your lawn. In the early stages, affected patches may recover with improved lawn care practices. However, if the disease is left untreated, the fungus can destroy the crown and root system of the grass, leading to permanent turf loss.
The most significant danger of Fusarium blight is its ability to weaken the lawn, making it more susceptible to other diseases, drought stress, and weed infestations. Even if some grass survives, the remaining turf may be patchy, thin, and less resilient to future problems.
How To Prevent & Treat Fusarium Blight
Aeration & Thatch Management: Core aeration helps relieve soil compaction and improves water infiltration, reducing stress on the root system. Dethatching is also essential if your lawn has excessive thatch buildup, as thick layers create a breeding ground for fungal spores. Aim to dethatch your lawn every few years if necessary, particularly if the thatch layer exceeds half an inch.
Proper Watering Practices: Water your lawn deeply and infrequently to encourage strong root growth. The best time to water is early in the morning, allowing the grass to dry throughout the day. Avoid watering in the late afternoon or evening, as prolonged moisture on the blades promotes fungal growth.
Fertilization & Soil Health: A well-balanced fertilization program can help prevent Fusarium blight by keeping your grass healthy and resilient. Avoid excessive nitrogen applications in the summer, as too much nitrogen can promote lush, weak growth that is more susceptible to fungal infections. Instead, use a slow-release fertilizer that provides consistent nutrients throughout the growing season.
Mowing Best Practices: Mow your lawn at the correct height for your grass type, keeping it slightly taller during hot weather to reduce stress. Always use sharp mower blades to avoid damaging the grass, and never remove more than one-third of the blade length in a single mowing session.
Fungicide Treatments (If Necessary): If Fusarium blight persists despite cultural control methods, fungicides may be required to stop the spread. Fungicides containing azoxystrobin, propiconazole, or thiophanate-methyl are effective against Fusarium blight. However, fungicides should only be used as a last resort, and they should only be applied by experienced professionals.
If you are looking for professional lawn disease control in Lincoln, Nebraska, call Summit Lawns today to restore your lawn to full health!
