Pathogen: Sclerotinia homeocarpa, Lanzia sp., Moellerodiscus sp. Susceptible grasses: bermudagrass, annual bluegrass, fescue, ryegrass, Seashore paspalum, zoysiagrass Symptoms: small, circular spots from 1–5 inches in diameter; spots might merge to form large, irregular areas; leaves appear watersoaked then brown, often exhibiting a reddish band across the leaf; fine, white cobwebby threads seen in early morning Conditions favoring disease: moderate temperatures (60°–80°F); excess moisture or water stress; fog; thatch; survives in soil as hard, dark structures (sclerotia) Prevention: fertilize adequately; reduce thatch; water appropriate length of time to a depth of 4–6 inches but don’t extend interval too long; maintain air circulation; compost top dressings can suppress disease Chemical treatment: if present in previous years, fungicide might be useful; apply in early spring or fall before symptoms occur
Pathogen: Agrocybe spp., Marasmius oreades, Lepiota spp., other Basidiomycete spp. Susceptible grasses: all lawn grasses Symptoms: a dark green band of turf develops in a circle (4 inches up to 30 feet) or semicircle in moist turf; mushrooms might or might not be present; an area of brown, dying grass might occur just behind the dark green band; a second ring of dying grass might appear inside the circle; weeds commonly invade Conditions favoring disease: soils high in thatch or undecomposed organic matter containing lignin Prevention: apply adequate nitrogen; aerate soil for better water penetration, water heavily in holes for several days; verticut if more than 1/2 inch of thatch accumulates; rake mushrooms to improve appearance of turf; to eliminate, remove turf and root zone containing white, cottony mass to a depth of 12 inches and 2 feet beyond outer edge of the ring; refill with clean soil and reseed or resod Chemical treatment: fungicides available, but control has been erratic
Pathogen: Fusarium culmorum, F. tricinctum Susceptible grasses: Kentucky bluegrass Symptoms: small, circular, grayish green areas, ranging from a few inches up to a foot in diameter; some plants in center can survive, giving a frog-eye appearance; the crown or basal area of dead stems has a reddish rot and is hard and tough; dead foliage appears bleached Conditions favoring disease: daytime temperatures of 85°–95°F; drought-stressed areas in full sun; survives in thatch and grass residues Prevention: water appropriate length of time; don’t apply more than 1 pound nitrogen/1,000 square foot/application or more than 6 pounds annually; use a mixture of 20% perennial ryegrass when seeding bluegrass; mow at highest recommended height; verticut if more than 1/2 inch thatch Chemical treatment: fungicides don’t give complete control in California; make application in spring before or just after symptoms appear
Pathogen: Pyriculria grisea Susceptible grasses: fescues, kikuyugrass, ryegrasses, St. Augustinegrass Symptoms: irregular blighted patches of turf with bleached spots with dark margins on leaves; ryegrass develops a fishhook appearance Conditions favoring disease: daytime temperatures of 85°–95°F; high humidity or rainfall; overwatered and overfertilized turf Prevention: irrigate properly; don’t overfertilize; reduce shading; increase air movement Chemical treatment: fungicides are available, but cultural controls are more practical
Pathogen: Microdochium nivale Susceptible grasses: annual bluegrass, bluegrasses, fescues, ryegrasses, zoysiagrass Symptoms: circular patches of 1–2 inches that can enlarge to 12 inches; leaves first appear watersoaked, then reddish brown, and finally bleached; minute, gelatinous spore masses sometimes seen on dead leaves; white or pinkish fungal threads might be seen in early morning; more prevalent in Central and Northern California Conditions favoring disease: consistently cool temperatures (40°–65°F) and wet conditions; high nitrogen applications in fall; neutral or alkaline soil pH; pathogen survives in grass residues Prevention: reduce shade and improve soil aeration and water drainage; water appropriate length of time; avoid excess nitrogen, especially in fall; maintain soil pH between 6.5–6.7. Chemical treatment: if a serious problem in past, have licensed applicator apply fungicide in fall before symptoms appear
Pathogen: Bipolaris spp. and Helminthosporium spp. Susceptible grasses: bermudagrass, bluegrasses, fescues, kikuyugrass, ryegrasses, zoysiagrasses Symptoms: circular to elongated brownish spots with brown centers and dark brown or purple borders on leaf blades, sheaths, and stems; crowns and roots frequently have a dark brown rot; crown-infected plants might die in hot, windy weather, leaving thinned areas throughout the turf; spores are windborne Conditions favoring disease: warm temperatures (70°–90°F) for bluegrasses, ryegrasses, and fescues; cool temperatures (60°–70°F) for bermudagrass and zoysiagrass; high humidity; low clipped turfgrass; most severe with excess nitrogen fertilization or deficiency Prevention: reduce shade; improve soil aeration and water drainage; avoid dry spots and too much nitrogen fertilizer; maintain as high a cutting height as possible Chemical treatment: fungicides available but often not warranted
Pathogen: Pythium spp. Susceptible grasses: all grasses Symptoms: small, circular spots (2–6 inches) that run together; blackened leaf blades rapidly wither, turn reddish brown, lie flat, stick together, and appear greasy; roots might be brown; in humid conditions, masses of fungal mycelium might appear Conditions favoring disease: low spots that remain wet; warm temperatures (80°–95°F daytime, >68?F night time); survives as spores in soil for long periods Prevention: reduce shading; improve soil aeration and water drainage; water appropriate length of time; avoid mowing wet grass and applying high levels of nitrogen during hot, humid weather Chemical treatment: fungicides available but primarily prevented by cultural practices in California
Pathogen: Rhizoctonia solani AG1-A, AG 3 Susceptible grasses: bluegrass, annual bluegrass, fescues, ryegrasses Symptoms: first appears as small, irregular brown patches or rings that can enlarge to many feet in diameter; centers might recover resulting in rings of diseased grass; leaves and sheaths become watersoaked, wilt, turn light brown, and die; in light infestations, roots usually not infected and plants often recover; soil-inhabiting fungus that forms fine, fungal threads in soil or on turfgrass Conditions favoring disease: excess thatch and mat along with high temperatures (80°–95°F); high humidity; soft, lush growth due to excessive nitrogen; most common in warm, inland areas Prevention: reduce shading and improve soil aeration and water drainage; water appropriate length of time to a depth of 4–6 inches; avoid excess nitrogen; maintain thatch less than 1/2 inch Chemical treatment: fungicide useful if disease severe in past or for seedlings in young turf
Pathogen: Rhizoctonia solani AG 2-2LP Susceptible grasses: bermudagrasses, kikuyugrass, St. Augustine grass, zoysiagrass Symptoms: first appears as small, irregular brown patches or rings that can enlarge to many feet in diameter; centers might recover resulting in rings of diseased grass; leaves and sheaths become watersoaked, wilt, turn light brown, and die; plants pull out easily from soil with rotten stolons, in light infestations, roots usually not infected and plants often recover; soil-inhabiting fungus that forms fine, fungal threads in soil or on turfgrass Conditions favoring disease: excess thatch and mat along with cool temperatures (60°–70°F); wet soil conditions Prevention: reduce shading and improve soil aeration and water drainage; water appropriate length of time to a depth of 4–6 inches; avoid excess nitrogen in the fall; maintain thatch less than 1/2 inch Chemical treatment: fungicide useful if disease severe in past
Pathogen: Laetisaria fuciformis Susceptible grasses: bentgrasses, bermudagrasses bluegrasses, fescues, ryegrasses Symptoms: red thread may kill turfgrass in patches that are 2–8 inches in diameter, or the disease may occur over large areas without killing the plants; pink web of fungal threads bind the leaves together; look for pink, gelatinous fungal crusts projecting from the leaves to help identify this disease Conditions favoring disease: common under conditions of mild air temperatures (60°–75°F) and extended periods of leaf wetness; often appears on plants deficient in nitrogen during periods of cool or warm temperatures if there is adequate moisture (e.g., excess irrigation or rainfall) Prevention: proper irrigation and fertilization can reduce the incidence; adequate nitrogen usually can prevent this disease from occurring; prevent drought stress by irrigating turfgrass based on evapotranspiration needs of the turfgrass; provide adequate air circulation; reduce shading Chemical treatment: fungicides rarely warranted except in severe cases
Pathogen: Puccinia species Susceptible grasses: all grasses Symptoms: irregular patches of weak turf covered with rust colored growth (spores) Conditions favoring diseases: moderately warm air temperatures (70°–75°F) and extended periods of leaf wetness favor development; turf that is deficient in nitrogen is more susceptible Prevention: maintain turfgrass vigor by following proper irrigation and fertilization requirements for turf species; mow regularly and remove clippings to reduce number of spores if lawn is infected Chemical treatment: follow proper cultural practices; fungicides shouldn’t be needed.
Pathogen: Ophiosphaerella korrae Susceptible grasses: bermudagrass, Seashore paspalum, zoysiagrass Symptoms: circular areas of dead grass 6–12 inches in diameter appear in spring when growth resumes; spots might coalesce to form large areas; typically affects turfgrass more than 2 years old Conditions favoring disease: affects dormant plants; most severe when soil temperatures are < 65°F; survives as sclerotia and in infected roots and stolons Prevention: remove dead grass; fertilize in summer to maintain vigor; don’t overfertilize in late summer; water appropriate length of time Chemical treatment: fungicides available but primarily prevented by cultural practices in California
Pathogen: Magnaporthe poae Susceptible grasses: bluegrasses, fine fescues Symptoms: circular, yellow or tan areas of dead and dying plants up to 1 foot in diameter; can have green, apparently healthy plants in center; roots, crowns, and stolons have dark brown fungal hyphae on them; vascular discoloration and cortical rot occur in later stages Conditions favoring disease: high temperatures (> 85°) in late spring through the summer; most severe when turf is mowed low or when soil moisture is excessive Prevention: aerate soil and apply slow-release nitrogen; improve drainage; reduce compaction; water appropriate length of time; don’t mow too low; control thatch; reduce soil pH if higher than 7 Chemical treatment: systemic fungicides in fall usually necessary when disease has been severe
Necrotic Ring Spot
So, Get Your Free Estimate
Our team consistently strives to make decisions that positively influence relationships with our co-workers and customers. Likewise, we commit ourselves to keeping strong company values, vision, and systems to provide measurable outcomes.