Dollar spot (Sclerotinia
homeocarpa, Lanzia sp., Moellerodiscus sp.) |
| SUSCEPTIBLE GRASSES |
SYMPTOMS |
CONDITIONS FAVORING DISEASE |
PREVENTION |
CHEMICAL1 TREATMENT |
| bermudagrass, fescue, ryegrass, annual bluegrass |
small, circular spots from 1-5 inches in diameter;
spots may merge to form large, irregular areas; leaves appear watersoaked,
then brown, often exhibiting a reddish band across the leaf; fine,
white cobwebby threads may be seen in early morning |
moderate temperatures (60° to 80°F), excess
moisture or water stress; fog; thatch; survives in soil as hard, dark
structures (sclerotia) |
apply up to 6 lb actual nitrogen/1,000 sq ft/year;
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 may suppress disease |
if present in previous years, fungicide may be useful;
apply in early spring or fall before symptoms occur |
Fairy
ring (Agrocybe spp., Marasmius oreades, Lepiota spp.) |
| SUSCEPTIBLE GRASSES |
SYMPTOMS |
CONDITIONS FAVORING DISEASE |
PREVENTION |
CHEMICAL1 TREATMENT |
| all lawn grasses |
a dark green band of turf develops in a circle (4 inches
up to 30 ft) or semicircle in
moist turf; mushrooms may
or may not be present; an area of brown, dying grass may occur just
behind the dark green band; a second ring of dying grass may appear
inside the circle; weeds commonly invade |
soils high in thatch or undecomposed organic matter
containing lignin |
apply adequate nitrogen; aerate soil for better water
penetration, water heavily in holes for several days; verticut if more
than 1/2-inch 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 ft beyond outer edge of
the ring; refill with clean soil and re-seed or re-sod |
fungicides available, but control has been erratic |
Fusarium blight (Fusarium
culmorum, F. tricinctum) |
| SUSCEPTIBLE GRASSES |
SYMPTOMS |
CONDITIONS FAVORING DISEASE |
PREVENTION |
CHEMICAL1 TREATMENT |
| bluegrasses |
small, circular, grayish green areas, ranging from
a few inches up to a foot in diameter; some plants in center may 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 |
daytime temperatures of 85° to 95°F; drought-stressed
areas in full sun; survives in thatch and grass residues |
water appropriate length of time; don't apply more
than 1 lb nitrogen/1,000 sq ft/application or more than 6 lb annually;
use a mixture of 20% perennial ryegrass when seeding bluegrass; mow
at highest recommended height; verticut if more than 1/2-inch thatch |
fungicides do not give complete control in Calif.;
make spring application before or just after symptoms appear |
|
| SUSCEPTIBLE GRASSES |
SYMPTOMS |
CONDITIONS FAVORING DISEASE |
PREVENTION |
CHEMICAL1 TREATMENT |
| annual bluegrass, bluegrasses, fescues, ryegrasses,
zoysiagrass |
circular patches of 1-2 inches that may 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
may be seen in early morning; more prevalent in central and northern
Calif. |
cool temperatures (40° to 60°F) and moist
conditions; high nitrogen applications in fall; neutral or alkaline
soil pH; pathogen survives in grass residues |
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 to 6.7; high levels of potassium
suppress disease |
fungicides do not give complete control in Calif.;
make spring application before or just after symptoms appear |
Leaf spot (Bipolaris spp.) |
| SUSCEPTIBLE GRASSES |
SYMPTOMS |
CONDITIONS FAVORING DISEASE |
PREVENTION |
CHEMICAL1 TREATMENT |
| bluegrasses, fescues, ryegrasses |
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
may die in hot, windy weather, leaving thinned areas throughout the
turf; spores are windborne |
warm temperatures (70° to 90°F), high humidity,
and closely clipped turfgrass; most severe with high nitrogen fertilization |
reduce shade; improve soil aeration and water drainage;
avoid dry spots and too much nitrogen fertilizer; maintain as high
a cutting height as possible |
fungicides available but often not warranted |
Pythium blight (Grease spot). (Pythium spp.) |
| SUSCEPTIBLE GRASSES |
SYMPTOMS |
CONDITIONS FAVORING DISEASE |
PREVENTION |
CHEMICAL1 TREATMENT |
| all grasses |
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 may be brown; under humid
conditions, masses of fungal mycelium may appear; survives as spores
in soil for long periods |
low spots that remain wet; temperatures in the 80° to
95°F range |
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 |
fungicides available but primarily prevented by cultural
practices in Calif. |
Rhizoctonia blight (Rhizoctonia
solani) |
| SUSCEPTIBLE GRASSES |
SYMPTOMS |
CONDITIONS FAVORING DISEASE |
PREVENTION |
CHEMICAL1 TREATMENT |
| bermudagrasses, bluegrass, fescues, ryegrasses, zoysia,
annual bluegrass |
first appears as small, irregular
brown patches or rings that may enlarge to many feet in diameter;
centers may 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 |
excess thatch and mat along with high temperatures
(80° to 95°F); high humidity; soft, lush growth due to excessive
nitrogen; most common in warm, inland areas |
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 |
fungicide useful if disease severe in past or for
seedlings in young turf |
Spring dead spot (Leptosphaeria
korrae) |
| SUSCEPTIBLE GRASSES |
SYMPTOMS |
CONDITIONS FAVORING DISEASE |
PREVENTION |
CHEMICAL1 TREATMENT |
| bermudagrass (mostly hybrid varieties) |
circular areas of dead grass 6-12 inches in diameter
appear in spring when growth resumes; spots may coalesce to form large
areas; typically affects turfgrass more than 2 years old |
affects dormant plants; most severe when temperatures
50° to 57°F; survives as sclerotia and in infected plant parts |
remove dead grass; fertilize in summer to maintain
vigor; don't overfertilize in late summer; water appropriate length
of time; overseeding with ryegrass may be beneficial |
fungicides available but primarily prevented by cultural
practices in Calif. |
Summer patch (Magnaporthe
poae) |
| SUSCEPTIBLE GRASSES |
SYMPTOMS |
CONDITIONS FAVORING DISEASE |
PREVENTION |
CHEMICAL1 TREATMENT |
| fine fescues; bluegrasses |
circular yellow or tan areas of dead and dying plants
up to 1 ft in diameter; may have green, apparently healthy plants in
center; roots, crowns, stolons have dark brown fungal hyphae on them;
vascular discoloration and cortical rot occur in later stages |
high temperatures (85° to 95°F) in late spring;
most severe when turf is mowed low or when soil moisture is excessive |
aerate soil and apply slow-release nitrogen; improve
drainage; reduce compaction; water appropriate length of time; do not
mow too low; control thatch; reduce soil pH if higher than 7 |
systemic fungicides in fall usually necessary when
disease has been severe |
