Lawn Disease can affect the healthiest of lawns. Diseases are enough to perplex all of us to no end. Many lawn diseases are not easy to identify and to distinguish from other problems such as pests or poor maintenance. Much like human diseases, lawn diseases can be difficult to properly diagnose and even harder to treat correctly.
The most common controls is to use a fungicide on your lawn. But before you head off to the nearest nursery or big box hardware store, be aware that treating everything with a fungicide is not the answer.
Some diseases do not respond to fungicides. However, good turf management practices usually are adequate to prevent serious damage. Integrated cultural practices for turf management andpest control will limit the need for fungicides. Disease development often is associated with the lack of proper application of these turf management practices: 1) selection and planting of an adapted grass variety, 2) sufficient water at the correct time, 3) timely fertilization with the right amounts and balanced nutrients, 4) regular mowing at the recommended height, 5) adequate sunlight and air movement, 6) maintenance of good soil aeration and drainage, and 7) thatch management.
The key factor is in identifying the disease before trying to create a regimen to cure the disease. This can be problematic for all but those specifically trained in identifying certain lawn diseases. A few diseases like red-thread are obvious in their identification. But other diseases are remarkably similar in appearance and require drastically different methods of treatment.
Some key factors and symptoms to help recognize disease include: size and shape of dead and dying plants, specific spots on leaves, quality of root system, leaf color and growth characteristics, time of year, and temperature when disease developed. When diagnosing a lawn disease it is helpful to have a record of treatments such as fertilizer, herbicides, mowing height and frequency, watering frequency and amounts.
Tips in Preventing Lawn Disease
Turf selection: When establishing a new lawn or renovating an existing lawn, select a turf species or mixture of species that is adapted to your site conditions and the level of
Management that you are willing to do to keep the turf growing well. Cool-season grasses (Kentucky bluegrass, perennial ryegrass, tall fescue, red fescue) are stressed during our hot, dry summers, and the warm season grasses (Bermuda grass, Zoysia grass) which turn brown after a frost and are invasive. Most peopleprefer the cool-season grasses, and of the cool-season grasses turf-type tall fescue under most situations is the best adapted for normal lawn use. It is more droughts tolerant, disease resistant, insect resistant and requires less fertilizer than bluegrass, ryegrass and fine fescues. It can be seeded or sodded. Turf-type tall fescue sod usually contains about 10 percent bluegrass for sod strength and ability to repair bare spots. Perennial ryegrass can be added when seeding for quick germination, because tall fescue is slower to germinate. Plant only high-quality seed or sod from a reputable supplier.
Soil and fertility management: Soil conditions including fertility are crucial for establishing and maintaining a lawn successfully. A balanced fertility program based on soil test results every 3 to 5 years and before seeding a new lawn will improve the vigor of plants and their resistance to diseases. Establishing lawns on new construction sites where topsoil may have been removed or only a thin layer is present is particularly difficult. The addition of organic matter in the form of topsoil, leaf mold, compost, or other source of organic matter is recommended.
Soil compaction: Soil Compaction can be a serious problem in a newly constructed lawn as well as in older lawns. Compacted soil excludes air and impedes water movement, which reduces root function, thus causing a decline in plant vigor and disease resistance. In new lawns, it is important to prepare the soil well. Make sure the seed bed is firm but not compacted. In established lawns, core aeration will relieve compaction and reduce thatch accumulation.
Nitrogen management: Nitrogen is the most significant influence on disease severity. Excessive applications of highly soluble nitrogen can favor diseases, such as brown patch, Pythium blight, and leaf spot. The succulent grass has thinner cells walls, which are more easilypenetrated by fungi. Conversely, turf grown in nutrient-poor soil can be prone to dollar spot, rust and red thread. Light applications of nitrogen to turf in this condition will stimulate turf to produce leaves faster than the fungus can infect them. Most of the nitrogen requirements for your lawn should be applied in the fall or early spring before April 30. Apply no more than 0.5 lb of nitrogen in the early spring with the balance applied in the fall. Most lawns require a total of 2-3 pounds of actual nitrogen per 1,000 sq. ft. per year. Kentucky bluegrass lawns are heavy feeders and require the upper limit, while tall fescue lawns require the lower suggested rate.
Mowing: Regular mowing is necessary to maintain quality turf. Mowing favors fungal infection by creating wounds and, in some cases, disseminating the fungus. Height of cut also influences disease susceptibility. Mowing too closely predisposes turf to several diseases by removing the youngest, most photo synthetically productive tissues. This causes a depletion of food reserves in the plant, which are needed for disease resistance and recovery from stress and injury. Remove no more than 1/3 of the leaf tissue at one time. Keep mower blades sharp. When grass is mowed regularly, clippings can remain on the lawn; they do not contribute to thatch and can reduce the nitrogen requirements of the lawn.
Water management: Water is necessary for spore germination and fungal growth. Proper use of irrigation can influence turf grass diseases. Frequency, timing, and duration of irrigation are important factors to avoid predisposing turf to diseases. At the extreme, over-watered turf is succulent and prone to infection. Waterlogged soils are not well aerated and root growth is hindered. Algae and mosses thrive in waterlogged soils, particularly where turf density is poor. On the other hand, droughty soils predispose turf to infection as well. Irrigate deeply but infrequently to avoid drought stress. This maintains the turf in good vigor and reduces the impact of diseases. In the summer, morning or afternoon is the preferred time to irrigate so that the turf has a chance to dry by nightfall. An alternative approach is not to water and let the
lawn go dormant and recover on its own when rainfall returns.
Thatch management: Thatch accumulation of more than ½ inch can restrict root growth and predispose turf to drought damage and diseases. Many turf grass pathogens can survive as saprophytes in the thatch layer. Summer patch, leaf spot, and melting-out diseases are a few of the diseases favored by excessive thatch accumulations. Regular core aeration in the spring or fall will reduce thatch accumulation and open compacted soils.
Rust: This foliar disease is usually seen in the fall. Rust-infected turf becomes reddish-brown or yellow. Rust begins as yellow-orange flecks on individual grass blades and develops into orange or brick-red pustules. Spores within the powdery pustule easily rub off when touched. A heavy rusting can cause leaf blades to die and thin strands of susceptible turf. Primarily perennial ryegrass and bluegrass are infected; most turf including Zoysia can be infected. Turf can be thinned but rarely is killed. Avoid low nitrogen and leaf wetness.
Fairy rings: This disease can be seen at any time of the year. Rings or arcs of dead grass bordered by inner and outer zones of dark green grass, or rings of very green grass without a dead zone. Rings can be from 1 to 4 feet in diameter or range up to 20 feet. Mushrooms may or not be present in rings. All turfgrass can be affected, especially at dry locations and poorly nourished turf. Avoid thatch, buried organic debris, and drought stress. Fertilize and rake mushrooms to mask symptoms. Core aeration of stimulated and dead zones and drenching with an organ silicone wetting agent may alleviate symptoms. Eventually the symptoms will disappear.
Summer patch: This root and crown rot occurs during the summer, especially during periods of high temperature and drought. Diseased areas are first light green then fade rapidly to a straw color (may be confused with wilting). These areas are often circular or sometimes irregular patches often with living grass or weeds in the center. Sometimes smaller patches can merge and blight large areas of turf. Patches can be sunken and leaves at the borders may have a bronzed appearance. Avoid high nitrogen, wet soil, compaction and low mowing.