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Cultural management of turf diseases

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Though it can be challenging to maintain intensively-managed turfgrass without fungicides, good cultural practices will reduce the need for fungicide applications and make necessary applications more effective. In fact, effective and well-timed cultural practices may minimize or eliminate the need for fungicide applications in lawns and other less intensely maintained turfgrass areas.

Starting right 


Prepare the site well. Remove stumps, construction materials and other debris. Improve drainage where necessary, and fill in low areas. Test soil pH and adjust to 6.0 to 7.0 if required. Break up soil clumps to provide a uniform area for seed or sod.

Choose seed or sod carefully (see Turfgrass Selection: Species and Cultivars). Inspect sod for diseases or other problems. Choose high quality, pathogen-free seed. Many disease resistant cultivars are now available and should be included in blends and mixtures. Genetic variability in turfgrasses will reduce the chance for epidemics that kill or damage large areas of turf.

General landscaping decisions can have significant impacts on turf health. Pruning of tree branches may increase light penetration to allow better turfgrass growth. Trees, shrubs, and other plantings should be placed to allow good air circulation, so turf will dry quickly after rain or dew. In very shady areas, shade-tolerant turfgrass cultivars or other groundcovers should be planted.

Seed should be planted only in well prepared soil with good drainage when temperatures stay in the range to allow rapid germination and establishment. Keep soil and seed moist, but do not over-water.

Routine Care

Fertilizers - Apply according to current recommendations and based on a soil test. Excess nitrogen will cause succulent growth that is more susceptible to disease. Avoid nitrogen applications (especially water soluble/quick-release fertilizers) during leaf spot season early in spring, during hot, humid weather, and just before dormancy in fall, which may leave turf more susceptible to snow molds and winter injury. Be sure, however, to meet the minimum nitrogen requirement for the turfgrass species and use as some diseases (e.g. red thread, rusts, and dollar spot) are encouraged when nitrogen is deficient.

Herbicides - Herbicides can stress turfgrasses and make them more susceptible to diseases. Apply carefully according to label directions and with attention to environmental conditions.

Some herbicides may have fungistatic effect and provide some degree of disease control. Noting fungistatic occurrences may be useful for reducing the amount of fungicide applied, by applying fungicides in combination with fungistatic herbicides.

Liming - Adjust pH according to soil test recommendations. Disease occurrence may increase at pH extremes (too high or too low). Lime applied late in autumn can increase Microdochium patch (pink snow mold) incidence and high pH can predipose turf to take-all patch infection during the spring. 



Mowing - Mowing wounds turfgrasses and can spread pathogens (disease-causing organisms). Minimize wounding and shredding of grass blades by keeping mower blades sharp and adjusted properly. If possible, mow when the turf is dry. Mow as high as possible for species and the turf use, using the maximum mowing height in hot weather. Avoid mowing more than one-third of the total height at each cutting to reduce stress to the root system. Mowing in autumn until turf stops growing can help to reduce damage from snow molds.

Watering - Water is necessary for good plant growth, but too much water floods open spaces in the soil, depriving roots of oxygen. Disease-causing fungi reproduce by spores that, like seeds, need water to germinate and infect turf. Dry turfgrass blades reduce disease by reducing infection. Deep and infrequent watering is strongly preferred to shallow, frequent watering to minimize leaf wetness and to encourage an extensive root system. Every effort should be made to not extend the duration of time blades are wet from dew or irrigation. Do not water in late afternoon or early evening. Night irrigation after dew appears may help conserve water, but is not recommended on hot, humid nights because it can increase some diseases (Figure 2). Avoid light, frequent sprinklings (syringing) except to prevent wilting in close-cut or shallow rooted turf and during hot, dry weather. In certain situations, keeping upper soil layers moist may help to reduce the occurrence of necrotic ring spot and summer patch.

Figure 2. When NOT to water turf

 

Thatch - Thatch is mostly composed of partially decayed above- and below-ground lateral stem tissue (stolons and rhizomes). A thin layer is beneficial in most turf situations. When thatch is more than 1/2” thick, it reduces nutrient and water absorption and harbors insect pests and disease pathogens. Prevent excessive thatch formation by providing adequate fertility in combination with aeration, verticutting and topdressing when needed. Mechanical removal of thatch is disruptive and should be accomplished in spring and late summer when time and conditions will allow for sufficient turf recovery.

Compaction - Several diseases (e.g. necrotic ring spot, summer patch, or athracnose basal rot) are worse in areas with compacted soil. Core aeration can help relieve soil compaction and improve turf quality. On some sites, traffic management may also be appropriate to minimize soil compaction.

Targeted cultural practices

Some sites have a history of disease problems, while others exist in a growing environment conducive to certain diseases.  For some pathogens, targeted cultural practices can go a long way towards preventing disease occurrence, reducing severity of disease when it does occur, and promoting recovery from damage. Table 18 details cultural management strategies for some of the most common turf diseases encountered in the Northeast.

Table 18. Cultural management strategies for common turf diseases.

Disease (Pathogens) Turfgrass Hosts* Season Cultural Management Strategies
Algae, Mosses all turfgrasses Apr – Nov Improve fertility and drainage. Alleviate compaction. Modify shade-causing agents to increase light penetration.

Anthracnose (Crown/Basal Rot)
Colletotrichum cereale

bentgrasses, annual bluegrass Mar – Sept Provide adequate N fertility. Avoid stress from too little or too much water and compaction. Raise mowing height.
Bentgrass Dead Spot Ophiosphaerella agrostis bentgrasses less than 6 years old on sand-based root zones. June – Sept Add N. Rake out and reseed.

Brown Patch
Rhizoctonia solani

all turfgrasses, tall fescue, bentgrasses, perennial ryegrass July – Sept In hot weather, avoid excess N and excess water. Avoid night watering. Remove dew from putting greens.

Brown Ring Patch (Waitea Patch)
Waitea circinata

annual bluegrass, rough bluegrass, creeping bentgrass Dec – July Apply adequate N for rapid recovery from damage. Dethatch and improve drainage. Symptoms can often be masked with N or iron.

Copper Spot
Gloeocercospora sorghi

bentgrasses June – Sept Avoid excess N. Minimize leaf wetness. Plant resistant cultivars.
Damping-off, Seed Rot
several fungi including Pythium spp., Fusarium and Rhizoctonia solani
all turfgrasses Apr – Oct Ensure careful seedbed preparation. Use good quality seed. Maintain soil moisture but avoid overwatering.

Dollar Spot
Sclerotinia homoeocarpa

all turfgrasses, bentgrasses, annual bluegrass June – Sept Avoid N deficiency and water stress. Minimize leaf wetness. Relieve compaction and excess thatch. Raise mowing height.
Downy Mildew (Yellow Tuft) Sclerophthora macrospora all turfgrasses May – Sept Avoid excess N and excess watering. Iron sulfate may mask symptoms. Improve drainage.
Fairy Ring (various fungi) all turfgrasses April – Nov Mask symptoms with N or iron. Core aerate and water. Fumigate or remove soil in severe cases.

Gray Leaf Spot
Pyricularia grisea

perennial ryegrass, tall fescue July – Nov Avoid excess N. Minimize leaf wetness. Reduce shade, lower mowing height.

Leaf Smuts
Ustilago striiformis

bentgrasses, Kentucky bluegrass April – Nov Avoid excess N in spring. Avoid water stress. Plant resistant cultivars. Collect clippings and discard.
Leaf Spots and Blights/ Melting Out
“Helminthosporium” spp. Ascochyta, Bipolaris, Curvularia, Drechslera, Nigrospora, Septoria, Leptosphaerulina
all turfgrasses, Kentucky bluegrass, bentgrasses, fine fescues April – Oct Avoid excess N, especially in spring. Raise mowing height. Minimize leaf wetness. Plant resistant cultivars.
Necrotic Ring Spot Ophiosphaerella korrae Kentucky bluegrass, esp. sod (3-4 yrs old), fine fescues, annual bluegrass June – Sept Avoid water and fertility stress. Avoid compaction and excess thatch. Utilize slow release N sources.

Powdery Mildew
Blumeria graminis

Kentucky bluegrass, fine fescues July – Sept Reduce shade and increase air circulation. Avoid excess N.

Pythium Blight
Pythium spp.

all turfgrasses, perennial ryegrass, bentgrasses June – Aug Avoid excess N and night watering in hot weather. Do not mow when wet or when disease is active. Improve drainage and air circulation.
Pythium Root Dysfunction Pythium volutum creeping bentgrass Sept – June Avoid excess N. Improve drainage. Aerate Regularly.

Pythium Root Rot
Pythium spp.

all turfgrasses, bentgrasses and annual bluegrass in sand greens Mar – Nov Improve drainage. Increase soil organic matter.
Red Thread Laetisaria fuciformis and Pink Patch Limonomyces roseipellis all turfgrasses, perennial ryegrass, fine fescues April – Oct in mild, wet weather Avoid N deficiency, water stress, and low pH. Minimize leaf wetness. Water deeply and infrequently. Improve light penetration and air circulation.

Rusts
Puccinia spp.

all turfgrasses, Kentucky bluegrass, perennial ryegrass July – Oct Avoid N deficiency and water stress. Minimize leaf wetness. Plant resistant cultivars. Reduce thatch. Raise mowing height and collect clippings. Water deeply and infrequently.

Slime Molds
various organisms

all turfgrasses June – Sept Mow or hose away. Fungicide applications are not necessary.
Snow Molds: Pink Snow Mold (Microdochium Patch) Microdochium nivale and Gray or Speckled Snow Mold (Typhula Blight) Typhula spp. all turfgrasses, bentgrasses Nov – April Avoid lush growth in fall. Continue mowing until autumn growth ceases. Avoid prolonged snow cover; do not allow excessive piling of snow on turf and reduce drifting with placement of snow fences. Fertilize lightly in spring to promote re-growth.

Summer Patch
Magnaporthe poae

fine fescues, annual bluegrass, Kentucky bluegrass July – Sept Avoid water stress and overwatering. Avoid compaction. Maintain adequate fertility. Lower pH in top inch of soil. Raise mowing height. Utilize slow release forms of N. Apply 2 lb/A MnSO4 annually in spring.

Take-all Patch
Gaeumannomyces graminis var. avenae

bentgrasses Mar – June Sept – Nov Avoid heavy lime applications. Lower pH in top inch of soil. Improve drainage. Apply acidifying fertilizers.

Yellow Patch (Cool Weather Brown Patch)
Rhizoctonia cerealis

bentgrasses, Kentucky bluegrasses, perennial ryegrass Nov – April Avoid excess N. Minimize leaf wetness. Improve drainage and air circulation.
* The most susceptible turfgrass species are in bold italics.