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Quick Reference Guide to Major Diseases Affecting California Turfgrasses
Frank Wong, Urban Plant Pathologist, UC Riverside
The information listed below is an alphabetical list of common turf diseases followed by a short summary. More detailed information on diseases, insects, weeds and other pests, and cultural practices that encourage healthy turf are available at the University of California Integrated Pest Management website (http://www.ipm.ucdavis.edu).
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Disease
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Symptoms and Signs
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Turfgrasses Affected
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Conditions Favorable For Disease Devlopment
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Cultural Controls
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Notes
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Anthracnose
(Colletotrichum graminicola)
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Irregular shaped dead patches of turf, up to several inches in diameter. Plants appear yellow to reddish bronze. Black, setate aceruvli on dead leaves.
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Annual and Kentucky Bluegrass, Ryegrasses, Fescues
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High temperatures (80ºF +), drought, high salt, low nitrogen.
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Provide adequate N-fertility, avoid drought stress followed by overwatering.
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Commonly seen on dying turf affected by heat, drought or salt stress.
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Bipolaris or Dreschlera Leaf Spot
(Bipolaris and Dresclera spp.)
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Irregular thinning patches of turf, several inches to feet in diameter. Plants yellow to brown with black spots or discreet lesions on leaves. Roots, crowns and stolons may be dark and rotted.
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Kentucky Bluegrass, Bentgrasses, Bermudagras, Fescues, Ryegrasses
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Temperature of 70 to 90ºF (ccol season grass) or 50 to 70ºF (bermudagrass) with high humidity, drought and salt stress, and high nitrogen.
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Avoid excess N, drought and salt stress, and manage irrigation to avoid prolonged leaf wetness.
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Common on stressed turf, usually found in areas with high humidity and shading that increases leaf wetness periods.
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Curvularia Blight
(Curvularia spp.)
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Irregular brown patches of dead turf, several inches to feet in size.
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Annual and Kentucky Bluegrass, Bentgrass, Bermudagrass, Fescues, Ryegrasses
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High temperatures (80ºF +), drought, high salt, low nitrogen.
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Provide adequate N-fertility, avoid drought stress followed by overwatering.
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Commonly seen on dying turf affected by heat, drought or salt stress.
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Dollar Spot
(Sclerotinia homoeocarpa)
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Small white to tan dead spots, about an inch in diameter or less. Hourglass shaped lesions on leaf blades. Small areas of cottony mycelia on dead turf.
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Annual and Kentucky Bluegrass, Bentgrass, Bermudagrass, Fescues, Ryegrasses
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Temperatures between 60 to 90ºF with high humidity or rainfall, and low nitrogen.
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Provide adequate N-fertility, manage irrigation to avoid extended periods of leaf wetness.
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Mostly on very closely mowed turf (less than an inch).
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Fairy Ring
(40+ species of different fungi)
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Dark green to yellow rings or crescents, up to several feet in diameter. Rings may become hydrophobic and necrotic. White mycelia often seen in thatch or soil.
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All turf types
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May occur under many temperature conditions (32 to 100ºF). Associated with high soil moisture and organic matter.
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Avoid excessive organic matter, manage thatch accumulation and aerify and deep water hydrophobic areas.
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Difficult to manage, areas that become hydrophobic are at risk for turf loss. Mask greening symptoms with N-applications.
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Disease
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Symptoms and Signs
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Turfgrasses Affected
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Conditions Favorable For Disease Devlopment
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Cultural Controls
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Notes
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Fusarium Blight
(Fusarium culmorum, F. rosea)
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Greyish green patches that turn tan to straw colored, several inches to a few feet in diameter. Areas may have a frog-eyed appearance. Crowns and stems dark black or reddish brown.
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Annual and Kentucky Bluegrass, Bentgrass, Fescues, Ryegrasses
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Day temperatures from 85 to 95ºF with night temperatures above 70ºF, high nitrogen, and drought stress.
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Avoid excess N, manage thatch and avoid drought stress. Use Kentucky Bluegrasses tolerant to the disease.
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Occurs mainly on drought stressed turf, but most common on Kentucky Bluegrass.
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Gray Leaf Spot
(Pyricularia grisea)
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Irregular shaped patches (several feet in size) of yellowing turf that dies out. Tan leaf spots with dark borders and white to grayish sporulation. On ryegrasses, plants appear “blasted”, on warm season grasses and fescues, distinct leaf spots are seen.
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Kikuyugrass and St. Augustinegrass (warm season)
Ryegrasses and Fescues (cool season)
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Moderate temperatures (70 to 90ºF), high humidity or rainfall, and high N-fertility.
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Manage irrigation to avoid extended periods of leaf wetness, increase air movement and reduce shading, avoid high N-fertility in the summer.
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Very severe on ryegrasses. Moderate on kikuyugrass, St. Augustinegrass and fescues.
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Microdochium Patch / Pink Snow Mold
(Microdochium nivale)
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Circular dead patches with a whitish to pink color; plants usually brown. Pinkish mycelia or spore masses usually seen on dead plants.
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Annual and Kentucky Bluegrasses, Bentgrasses, Fescues, Ryegrasses
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Cool, wet weather (32 to 65ºF), and high nitrogen fertility.
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Avoid excess N, increase mowing heights.
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Most common on closely mowed annual bluegrass or turf covered by snow.
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Kikuyugrass Decline
(Gaeumannomyces graminis var graminis)
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Yellowish patches of turf up to several feet in size that slowly decline and die. Black mycelia evident on roots and stolons
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Kikuyugrass
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High soil pH, water logged soils, drought stress, low soil Manganese.
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Lower soil pH and amend with manganese. Avoid saturating soils with water in cool weather, but provide adequate irrigation in the summer.
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Most common on drought stressed turf. Damage to roots occurs in cool weather, but sometimes may not be evident until plants are water stressed.
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Pythium Blight
(Pythium aphanidermatum, other Pythium spp.)
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Circular spots a few inches in diameter that may run together, often occurs in “streaks” across lawns. Affected plants reddish to black and greasy appearing. White, fluffy mycelia often present in morning.
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All turf types
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Hot humid weather (85ºF +, 90% RH) and above 68ºF at night, high nitrogen fertility, and excess water.
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Avoid excess N and overwatering. Avoid mowing when grass is wet.
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Can occur very rapidly, killing turf in 24 hrs or less. Avoid planting new turf or seeding turf when conditions are optimal for disease development.
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Disease
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Symptoms and Signs
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Turfgrasses Affected
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Conditions Favorable For Disease Devlopment
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Cultural Controls
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Notes
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Red Thread
(Laetisaria fuciformis)
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Pink to reddish circular patches up to several inches in diameter. Pink fungal crusts can be seen covering leaf blades.
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Annual and Kentucky Bluegrass, Bentgrass, Bermudagrass, Fescues, Ryegrasses
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Moderate, wet weather (60 to 75ºF) with low N-fertility.
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Provide adequate N-fertility, and manage irrigation to avoid prolonged leaf wetness.
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Most common on ryegrasses, rarely seen on other turf types in CA.
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Rhizoctnia Blight/Brown Patch
(Rhizoctonia solani)
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Circular brown patches or rings up to a few feet in diameter; edges may appear grayish. White mycelia often seen in the morning. Individual plants light brown or have lesions with reddish/purple borders.
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All turf types
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Cool season grasses usually attacked during periods of hot weather (above 85ºF) with excess irrigation. Warm season grasses attacked in cool wet weather or during spring/fall transition periods (60ºF range). Common on high N-fertility turf with heavy thatch accumulation.
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Avoid excess N-fertility, manage irrigation to avoid prolonged leaf wetness, and reduce thatch accumulation.
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Most common on over-irrigated fescue lawns in the summer and bermudagrass emerging from dormancy.
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Rust
(Puccinia spp.)
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Orange-tint to turf that usually occurs in large irregular patches. Orange pustules and spores visible on leaves.
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Bluegrasses, Fescues, Ryegrasses
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During moderate temperatures (70 to 80ºF) on low N-fertility turf. High humidity or excess leaf moisture help disease development.
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Provide adequate N-fertility, and manage irrigation to avoid prolonged leaf wetness.
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More common in shaded areas and those with poor air movement.
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Southern Blight
(Sclerotium rolfsii)
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Reddish rings or crescents, several inches to feet in diameter. Small light to dark brown sclerotia visible in soil and thatch. White mycelia visible at the margins of the rings.
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Bentgrasses, Bluegrasses, Fescues, Ryegrasses
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High temperatures (85 to 95ºF) with high humidity, rainfall or soil moisture.
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Provide adequate N-fertility, manage thatch accumulation and manage irrigation to avoid prolonged leaf wetness.
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Most severe on turf subjected to extreme wet/dry cycles. Sclerotia can be moved on equipment to new turf.
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Spring Dead Spot
(Ophiosphaerella korrae, Ophiosphaerella namari)
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Tan to straw colored patches of dead bermudagrass up to several feet in size that does not emerge from dormancy in the spring.
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Bermudagrass
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Excessive N-fertility in the fall, high soil pH
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Manage thatch accumulation, reduce fall N-fertility, reduce soil pH, promote healthy growth and establishment during spring and summer.
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A disease of bermudagrass only. Fungus attacks dormant stolons and roots resulting in turf that cannot recover from dormancy.
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Summer Patch
(Magnaporthe poae)
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Tan to reddish circular patches or rings, up to several inches in diameter. Affected crowns are dark brown.
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Bentgrasses, Bluegrasses, Ryegrasses
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High temperatures (above 85ºF), low N-fertility, drought and salt stress.
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Provide adequate N-fertility, manage irrigation to prevent drought stress, but do not over saturate soil.
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Most common on drought stressed turf. Infections occur when soil temperatures are above 68ºF, but symptoms not seen until warm weather.
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Disease
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Symptoms and Signs
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Turfgrasses Affected
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Conditions Favorable For Disease Devlopment
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Cultural Controls
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Notes
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Take-All Patch
(Gaeumannomyces graminis var avenae)
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Reddish rings or crescents, several inches to feet in diameter.
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