Your Guide to Identifying 15 Common Lawn Diseases
Does your grass appear uneven, discolored, or strange in any way? It’s critical to take prompt action to detect and eradicate grass disease before it spreads across your property since it may significantly harm your lawn quickly.
This book details the symptoms and underlying causes of 15 prevalent lawn illnesses.
Brown Patch
Description: During hot and muggy conditions, a leaf disease called brown patch may develop on your lawn. Initially, Brown Patch frequently manifests as rough, round patches ranging from a few inches to several feet wide. Fungal growth is what you can see in the early morning dew that resembles purple or grayish-brown cobwebs. Tall fescue, perennial ryegrass, and creeping bentgrass are susceptible to severe damage from the disease, although Kentucky bluegrass is rarely harmed.
Causes: The fungus Rhizoctonia infects the leaves and crowns of grass, resulting in brown patches. Under stressed circumstances, this fungus can cause illness in the grass plant by colonizing the organic debris in the thatch layer. When temperatures rise over 85°F and relative humidity levels are high, brown patches will likely appear on cool-season grasses.
Dollar Spot
Description:The fungus Rhizoctonia infects the leaves and crowns of grass, resulting in brown patches. Under stressed circumstances, this fungus can cause illness in the grass plant by colonizing the organic debris in the thatch layer. When temperatures rise over 85°F and relative humidity levels are high, brown patches will likely appear on cool-season grasses.
Causes: The fungus Sclerotinia homoeocarpa, which causes Dollar Spot, grows best in warm, humid environments and spreads through grass blades via airborne contact. Additionally, shoes, other yard tools, and mowing equipment might spread it.
Fairy Ring
Description: Dark green, circular rings on the grass signify Fairy Ring disease in the early summer. Though observing an unformed circle is sometimes normal, the Fairy Ring typically develops in a circular pattern. The width of bands can range from 4 to 12 inches, while the diameter of rings can reach up to 50 yards. Mushrooms and toadstools may sprout around the rings under rainy weather conditions.
Causes: The fungus known as Marasmius oreades, or the Fairy Ring Mushroom, is the cause of the Fairy Ring. As deep as 12 inches beneath the surface, the fungus is confined to the soil and produces mushrooms that can vary in size from a few inches to several feet across. Along the inner edge of the rings, it spreads outward after attacking at a central place, where the grass weakens and frequently momentarily dies off. The weakening grass may cover the whole core region in tiny rings. The fungus consumes decomposing organic waste in the soil and can also change the development of grass, making it either thinner or thicker than the grass around it. Dead organic materials, such as leaves or tree stumps, high soil moisture content, and inadequate drainage can all lead to the formation of the Fairy Ring.
Leaf Blight
Description: Cool-season turfgrasses, including Kentucky Bluegrass, Tall Fescue, and Perennial Ryegrass, are commonly afflicted by Leaf Blight disease. Long, water-soaked sores on the leaves are a sign of leaf blight. These lesions gradually become yellow or brown and may even kill the leaves. The damage frequently forms Large, bleached regions, manifesting as circular patches in strongly infected grass. A closer look at the lawn shows that each blade of grass is turning yellow from the tips down.
Causes: After the lawn is cut in the evening and then overwatered at night, leaf blight typically infiltrates the grass plants. The fungus that causes the sickness is especially prevalent in warm, humid climates. Both foot traffic and mowing or watering machinery can spread it. All things considered, homeowners may find Leaf Blight disease to be a difficult issue, but it is manageable with the right care and attention.
Gray Leaf Spot
Description: In the warm, humid parts of the United States, warm-season grasses including Bermuda, Zoysia, St. Augustine, and Tall Fescue are susceptible to a fungal disease called Gray Leaf Spot. The disease manifests as tan, round or oval lesions with brown or purple edges on the turf’s leaf blades. In extreme situations, the leaves may wither and die, and lesions may appear on the leaves, sheaths, and stems. Large sections of the lawn may occasionally be destroyed as the illness worsens and the afflicted region gets bigger. The grass may also start to thin down, turn brown, and die. The illness can cause terrible harm if it is not managed.
Causes: The fungus Pyricularia grisea, which grows best in warm, humid areas, is the source of gray leaf spot.
Leaf Spot
Description: Because of their comparable symptoms and effects on turfgrass, Leaf Spot and Melting Out disease are frequently combined. On the grass plant’s leaves, leaf spots will show up as tiny, round or elongated patches. Usually brown or tan in hue, these patches have purple or reddish edges. The patches may get larger and meld together as the condition worsens, ultimately resulting in the grass blades becoming brown or yellow and dying.
Causes: A disease that causes the most harm in the summer months is frequently the source of leaf spot.
Melting Out
Description: Leaf Spot disease and Melting Out disease both affect turfgrass and have comparable symptoms. As the condition worsens, the fungus penetrates the base of the plant and targets the crown and roots, although Melting Out is initially identified by the discolored patches on the grass blades. The lawn is thin, scruffy, and yellowish, with sporadic areas of dead grass. Raking is simple to remove dead grass plants from these impacted regions. It can harm most cool-season grasses, although it usually damages warm-season grasses like bermudagrass and zoysiagrass the most.
Causes: In chilly, rainy conditions, the Melting Out pathogen is active.
Necrotic Ring Spot
Description: A fungus called Necrotic Ring Spot damages cool-season turfgrass, including Kentucky Bluegrass, Perennial Ryegrass, and Fine Fescue. It produces circular areas of dead grass with a healthy-looking core surrounded by a noticeable brownish-yellow rim. Though they can vary in size, the rings typically have a diameter of one foot. Because of the form of the rings, it is also referred to as “Frog Eye.”
Causes: Although signs of Necrotic Ring Spot are most obvious in the cold spring months, they can appear at any time throughout the growing season when the fungus is active. Symptoms typically reappear during the hot, dry summer months because the sickness is often made worse by stress from drought and heat.
Powdery Mildew
Description: Although any turfgrass can get powdery mildew, annual bluegrass, bentgrass, and fescues are the most susceptible. The fungus damages plant tissue by feeding on it and producing a white or grayish powdery covering on the leaves and stems. The grass may weaken and grow stunted, and the afflicted leaves may also become yellow or brown.
Causes: The most prevalent seasons for powdery mildew to occur are spring and fall, when temperatures range from 55°F to 70°F. It may spread quickly in places with a lot of shadow, at times when light is weak, and when air circulation is poor.
Pythium
Description: All kinds of turfgrass, including lawns, golf courses, and sports fields, are susceptible to the fungal disease known as Pythium Blight. Pythium Blight turns grass brown and kills it, often in a matter of hours, if the right circumstances are present for the fungus. The grass will seem oily, the leaves will suddenly wilt or turn yellow, and the afflicted region will smell bad. A cottony, purplish-gray, or white mass known as mycelium will clump together water-soaked leaves. Because the spores and mycelium are dispersed by mowing machinery or drainage patterns, damage to the lawn frequently manifests as lengthy streaks.
Causes: High nitrogen fertility from fast-release nitrogen aggravates pythium blight, which is mostly seen on poorly drained soils with a pH higher than 7.0. Controlling the illness is challenging because it spreads quickly and flourishes in warm, humid conditions. The fungus develops more slowly in cooler weather and usually does not infect foliage; however, it might occasionally cause the roots to rot.
Red Thread
Description: Common fungal diseases like Red Thread disease, or “Pink Patch,” impact cool-season turfgrasses like Kentucky Bluegrass, Perennial Ryegrass, and Fine Fescues. Red Thread is extremely difficult to regulate or avoid since it can emerge overnight under the right circumstances. The fungus causes the ends of the brown grass blades to take on a round or irregular form, producing thread-like strands or web-like masses that vary in color from coral pink to deep red.It is called “Red Thread” because the strands are visible and can extend up to 1⁄2 inch above the blade. The condition can cause patches that are uneven or round, and they can get up to 6 inches in diameter. As the illness worsens, the patches may grow, blend together, and become more noticeable, resulting in a weak, thin, and unsightly lawn.
Causes: Red thread disease is most common in warm, humid weather, especially in nutrient-deficient or poorly drained soils. It is most common in temperatures between 60°F and 75°F during humid spring and fall seasons.
Rust
Description: Numerous kinds of turfgrasses are susceptible to the fungal disease rust. It gets its name from the rust-colored patches it leaves on the grass blades, which are either orange or brown. Thin and uneven lawns can result from the disease’s ability to cause grass plant leaves to wilt, become yellow, and eventually die. Rust prefers warm, humid weather, and it is most common in late summer and fall when there is little light and temperatures between 70°F and 80°F.
Causes: A kind of fungus that is frequently present in soil and plants is the source of rust. It lives on dead and living leaf tissue on the lawn’s thatch layer. The illness will spread quickly when the right circumstances are met. Several things, such as poor irrigation, excessive humidity, and erratic weather patterns, can cause the growth of rust. Large quantities of reddish-orange spores form on the grass plants’ leaves. They are easily transferred to shoes, clothes, animals, lawnmowers, and other items that come into contact with the affected areas. However, the grass usually recovers when circumstances improve and cultural behaviors change.
Slime Mold
Description: On occasion, the slime mold will cover the leaf blades with a thin coating of a sticky, paste-like substance. It can take on a variety of hues and eventually dry down to produce powdery growths on the leaves. It does not immediately injure lawns and poses no threat to people or animals. However, householders who are unfamiliar with the organism may find it ugly and worry.
North America is home to several species of slime molds. Their appearance and behavior vary, but they all have the trait of being slimy and gelatinous. Both warm- and cool-season grasses can be impacted, and they are not exclusive to certain kinds of grass. Among the most popular types of slime mold are Black Slime Mold, Dog Vomit Slime Mold, Yellow Slime Mold, and Purple Slime Mold.
Causes: A fungus-like creature called slime mold may grow on lawns, especially in wet or humid environments. It can quickly cover a lot of grass. Slime mold may be a sign of too much organic matter in the soil, such as decaying leaves or other detritus because it feeds on bacteria and other microbes.
Snow Mold
Description: In areas with snow cover and severe winters, residential lawns are frequently affected by the fungus known as snow mold. Pink and gray snow mold are the two varieties of snow mold. The more prevalent of the two, gray snow mold manifests as round areas of light brown or grayish-white lawn grass. Less frequent but more severe, pink snow mold manifests as round patches of sticky, pinkish grass.
Causes: Fungal spores proliferate and become active under the snow throughout the winter, which is what causes snow mold. Snow that remains on the grass for a long time creates a damp, humid atmosphere that is perfect for the development of fungus spores. Snow mold is more common in grass areas that are shaded or have inadequate drainage.
SUMMER PATCH
Description: The annoying lawn ailment known as “summer patch” usually appears during the hot, muggy summer months, when grass should flourish. Cool-season grasses, including Kentucky Bluegrass, Tall Fescue, and Fine Fescue, are most impacted. Your yard is much more at risk if it has a lot of thatch or inadequate drainage. Patches of the grass will begin to turn yellow or brown; in certain places, it may appear as though the lawn is withering entirely. These patches, which occasionally form rings or are merely asymmetrical blotches, might be tiny or extend for many feet. It’s unattractive and may be a major pain if you’ve put a lot of effort into your grass.
Causes: Magnaporthe poae is a fungus that infects the turfgrass plant’s roots and crown, causing Summer Patch. Where the grass is exposed to direct sunlight, such as on south-facing slopes or close to sidewalks, roadways, buildings, or other stressed places, damage from this disease is likely to develop. The grass can start to grow back into these dead spots in the chilly fall temperatures.
YELLOW PATCH
Description: Yellow patch symptoms include areas on the grass that are yellow, brown, or tan, which can be anywhere from a few inches to several feet across. There can be a noticeable golden border around the spots. The grass could seem thin or sparse in the impacted regions and be stunted. In extreme situations, the patches can combine to create huge, asymmetrical swathes of dead or dying grass. The lawn’s general health may deteriorate due to the impact on the grass plants’ roots and crowns. Although the damage is often superficial, thinning may happen with extended rainy spells in the late winter or early spring.
Causes: Yellow patch is a fungus that may affect grasses that grow in both warm and cool seasons. From late fall to early spring, it is most prevalent when temperatures are lower, and there has been more rainfall than normal.
Controlling Lawn Diseases
The best defense against lawn disease is always thick, healthy, and well-kept grass. Changes in weather and temperature will usually slow the disease’s progress, but you may also modify some cultural practices to enhance grass health and slow its spread.
- When grass disease is active, do not water.
- When grass disease is active, do not mow. To reduce the transmission of illness, if you must mow, make sure the blades are sharp.
- Apply fertilizer on a regular basis.
- By allowing water and nutrients to permeate the soil, improving drainage, and lowering compaction, aeration lowers the risk of grass disease.
Other methods of control could be required, and you might need to use sod or the proper grass seed to restore severely damaged areas, depending on the extent of the infestation and the extent of the damage.
If you think your lawn may be suffering from any of the aforementioned ailments, contact your neighborhood Weed Man for a diagnosis and personalized treatment advice.
