Identifying Florida Lawn Diseases


Identifying Florida Lawn Diseases

 

Brown Patch Fungus Disease - Brown patch disease is caused by a species of Rhizoctonia fungus. It usually occurs in St. Augustine, Bermuda, Bahia, and Centipede grasses. Brown patch fungus typically begins in a small area of the lawn, but can spread quickly. The initial sign of the disease is a yellowing of the foliage. Affected blades are easily pulled from the stolon because the fungus destroys the tissue at the leaf base. Infected areas will typically appear in a circular pattern. Surviving sprigs will often sprout in the center, giving a ring appearance. Brown patch thrives in warm, humid conditions. A fungicide is necessary to control Brown Patch Fungus.

Brown Patch

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Grey Leaf Spot Disease - Grey leaf spot disease is caused by the fungus Pyricularia grisesa, mainly affects St. Augustine grass, and it occurs during warm, humid weather. Oblong leaf spots are the most diagnostic disease symptom. The center of the leaf spot may have gray felt-like growth of sporulation after extended periods of warm, moist conditions. A leaf spot may appear olive green to brown in color, with a dark-brown border when sporulation is not present. When the disease is severe, grass may appear thin and generally unhealthy. Entire shoots or blades can turn brown if the disease progresses. Gray leaf spot can significantly reduce the vigor of the turf. The disease develops more rapidly and more severely on lush leaf tissue. Extended periods of leaf wetness favor infection and spread of the pathogen and increase the likelihood of disease. Best application results occur when fungicides are applied preventatively, according to the label, and while environmental conditions are favorable and while environmental conditions are favorable for disease development during the grow-in. If this disease becomes a serious issue, then contacting a lawn care service is recommended.

Grey Leaf Spot

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Fairy Ring Fungus - Fairy Ring fungus appears as rings of dark green or dead grass.  This fungus usually appears in hot conditions during period of ample rain. It grows underground, in an outward fashion, along the root system of the grass. This fungus grows in a circular pattern that breaks down the organic matter in the soil. This biodegradation of organic matter releases nitrogen causing the infected grass the appear dark green. Fairy ring fungus fruits mushrooms which appear on the outer edge of the ring. The fungi produce a mass of cotton-like webbing called mycelium. As the mycelium dies, it may harden to a point where water will not be able to penetrate through it. This results in the death of the grass above it. Fairy Rings can be difficult to control. In the areas where the grass has died, increased water penetration must be achieved by core aeration or by creating holes in the rings. This can create an opportunity for a fungicide containing dichlorophen to reach the infected area, although fungicide applications have had an inconsistent history controlling Fairy Ring. In severe cases, a resodding/resoiling of the area may be needed to eradicate the fungus. One of the most effective ways to prevent Fairy Ring is to remove large piece of woody material (stump, dead tree roots) before turf is placed. Another proven method is to have a turf management program consisting of proper fertilization and a regular dethatching and aerating schedule. 

Fairy Ring

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Dollar Spot - Dollar Spot is caused by the fungus Lanzia spp. and Moellerodiscus spp., which produces 2”-6” blotchy, circular areas. These patches can coalesce to become large straw-colored areas of turf. It develops in humid conditions at temperatures ranging from 60-85 degrees. In the initial stages of disease, leaves develop tan spots and bands and a reddish-brown border can often be seen on the leaf spots. Lesions on leaves have a distinctive hourglass shape with necrosis on the outer edges of the blade and healthy tissue in the middle. Fine, white, cobweb-like hyphae (fungal threads) may be noticed early in the morning.  Dollar Spot can be controlled by various methods of biological control including composted materials, bacterium, fungus, and the application of nonpathogenic strains of S. homoeocarpa. BioJect Spot-Less and EcoGuard are two biological control products that are currently registered for dollar spot control. Worldwide, more money is spent on the chemical control of dollar spot than any other turfgrass disease. 

Dollar Spot

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Rust - Rust is a relatively easy lawn disease to identify in your lawn. Temperatures between 60-85 degrees (early Spring-Fall), low-light/low-nitrogen areas  and drought-stricken areas are favorable development conditions. In the beginning disease stages, it causes yellow flecks on the grass blades and sheaths. The flecks enlarge and elongate over time, turning dark-yellow in color. These areas then rupture, releasing spores that are yellowish-orange to reddish-brown in color (hence the name “Rust”). A severe disease infection can cause the entire turfgrass shoot to turn yellowish to reddish-brown in color and slow growth in your lawn. Turf may appear to be thin as individual shoots begin to die. Towards the end of the Rust disease infection cycle, leaves may become shredded and point downward if the infection is severe enough. Also, plants infected by rust are more susceptible to infection from other turfgrass diseases. Rust can be controlled by the use of the fertilizers with adequate levels of nitrogen, reducing thatch with core aeration, and appropriate watering cycles. Treatment of Rust can be provided by fungicides like Triadimefon and Anilazine.

Rust

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Take-All Root Rot - Take-all Root Rot usually initially appears in the spring and summer as yellowing patches of grass, ranging in size from a few inches to a few feet in diameter. Turfgrass roots will be whitish in color with sporadic black lesions. The stolons and rhizomes of the grass plants may also have black lesions. Affected areas of the turf will be easily removable, whereas healthy turf is difficult to remove, since the roots remain unaffected by rot and are firmly attached to the soil. By attacking the roots of the grass, Root Rot limits its ability to effectively absorb water and vital nutrients. Tips for controlling Root Rot include raising lawn mowing height during high-risk disease conditions, applying high levels of potassium with a balanced fertility program, and using slow-release forms of nitrogen applications. If these methods are ineffective, there are professional products on the market to control Take-all Root Rot.

Take-All Root Rot

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