Lawn Diseases

Brown Patch

Brown patch is a fungus disease that’s most common to Bermuda, Kentucky bluegrass, centipede grass, bentgrass, St. Augustine and ryegrasses in regions with high humidity and/or shade. Brown patch starts as a small spot and can quickly spread outward in a circular pattern. Often, the inside of the circle will recover, leaving brown areas that resemble a smoke ring. Symptoms first appear as small, circular patches of water-soaked, dark grass that soon wilts and turns light brown.

Brown patch can be controlled somewhat by following a strict fertilization schedule that only applies the proper amount of nitrogen and trace elements during the ideal times. Mowing the grass a little taller with a sharp mower blade and bagging lawn clippings (when possible) can also decrease the chances of brown patch. Fungicide applications are most effective when used preventively before the disease has become established in the lawn. The best prevention for brown patch is to aerate often, reduce shade in affected areas, and follow a fertilization schedule that avoids excess amounts of nitrogen.

Necrotic Ring Spot

Necrotic ring spot frequently occurs on two- to five-year-old sodded lawns and is especially prevalent in vigorously growing turf. These lawns often develop a thick thatch layer that stimulates fungal growth. Necrotic ring spot is also common in lawns that have layered soil: 1″ to 2″ of topsoil laid down over hard, compacted native soil (but not mixed together). This effect produces a lawn with shallow roots and poor drainage. Damage is most evident in the summer. During hot, dry weather, damaged root systems can no longer support the plant – and the entire plant dies.

Fungicides can manage the disease preventively, but they’re of limited use once disease symptoms are visible. Lawns that are compacted or have thick thatch layers promote the development of necrotic ring spot. Aeration and dethatching will reduce compaction, increase nutrient and water penetration, and increase microbial activity to help decompose the thatch layer. Reseeding dead areas with resistant varieties of bluegrass may expedite the recovery process.

Dollar Spot

Dollar spot attacks grasses such as bentgrass, hybrid Bermuda grasses and zoysia. The disease occurs from spring through fall, and is most active during moist periods of warm days (70° to 85° F) and cool nights (60° F). Dollar spot is spread from one area to another by water, mowers, other equipment or shoes.

The disease appears as round, brown, sunken spots approximately the size of a silver dollar. Dollar spot is identified by lesions on the leaf blades of live plants near the border of the affected area. The lesions are light tan with a reddish-brown border, and usually radiate from the margins of the leaf blade. On fine-bladed grasses such as bentgrass, the lesions usually girdle the leaf blade. To prevent dollar spot, fungicide applications during moist weather in the spring, early summer and fall are most effective.

Rust

Rust first appears as small, yellowish flecks in infected leaf blades. Later, hundreds (if not thousands) of orange to reddish-brown spores are released from the leaf. Leaf infections occur when days are dry and windy followed by heavy dew formation at night. The dry, powdery spores are easily spread by wind currents.

Fertilizing and irrigating to promote grass growth are the best ways to control rust. Deep, infrequent watering is best, along with frequent mowing and clipping collection when possible. Several fungicides will aid in the control of rust, but multiple applications are generally required.

Snow Mold

Patches of matted, silver-gray or bleached-white turf signal snow mold. It often shows up in the spring after the ground thaws and new snow falls on the unfrozen lawn surface. It rarely does permanent damage, but to speed break-up, affected areas can be raked lightly. Prevention by mowing late in the fall and fertilization from The Turf Doctor to speed recovery are good ideas.

Red Thread/Pink Patch

A pinkish cast to the lawn is an early sign of red thread. Gelatinous pink fungus forms red, thread-like strands. Areas then brown and dry out. If this is a persistent problem in your lawn, overseeding with a more resistant variety of grass may help.

Leaf Spot

Leaf spot shows up as purplish-brown spots with lighter centers on grass blades. The tips often die as spots girdle blades, and dead lawn patches may result. It can progress to a more serious condition known as melting out. To keep ahead of leaf spot, control thatch (through core aeration from The Turf Doctor), mow a little longer, and have us fertilize appropriately.

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