رویان

بزرگترین مجله کشاورزی اینترنتی

رویان

بزرگترین مجله کشاورزی اینترنتی

Diseases شناسنامه بیماریهای گیاهی

One of the best weapons against disease in turf's is to create a healthy plant. In almost every case, weeds, insects and disease seek plants that are in stress. If a grass is growing in a healthy, balanced soil, if it is mowed correctly and watered properly it will be able to withstand almost anything that comes it's way. If it is deficient in any of these categories, it can be taken over or killed quit easily.

If chemicals are needed, first identify the disease. This section will help you. After you have succeeded this, then you can come to our fungicide page. This will help you decide which chemical will be best suited for your needs.

Diseases

Turfgrasses affected in distinct patches are: Dollar Spot, Fairy Ring, Pythium Blight, Brownpatch, Fusarium blight and Spring Dead Spot.

Turfgrasses not affected in distinct patches are: Rust, St. Augustine Decline, Gray Leaf Spot, Helminthosporium Leaf Spot and Powdery Mildew.

Spots not distinct on leaf blades are: Summer Brownpatch, Nematodes, Nitrogen or Iron deficiencies.

Turfgrasses affected in distinct circular patches or streaks are: Poor application of fertilizer, Improper mowing, chemical burn or petroleum spill.

DOWNY MILDEW

Turf Affected:

St. Augustine, Kentucky bluegrass, bentgrasses, ryegrasses, tall fescue and creeping red fescue.

Season:

Spring, early summer, and fall.

Conditions For Development:

Cool humid weather in the 60 to 70 degree range.

Early Symptoms:

White raised linear streaks that develop parallel to the mid-vein of the leaves.

Late Symptoms:

A fungal growth appears on the leaves and the tips of the leaf die. It can be confused with St. Augustine decline but it can be distinguished by less yellowing and more striping.

FAIRY RINGS

Turf Affected:

All lawn grasses.

Season:

Early spring to late fall.

Conditions For Development:

Introduced into new areas as bits of mycelium. Two to three years are required from the time of placement until the first-formed ring appears.

Early Symptoms:

Continuous circles of bands that are darker green and faster growing than the surrounding areas.

Late Symptoms:

Fruiting bodies of fungi appear. Usually called mushrooms, these structures may be quite abundant throughout the infected areas.

FUSARIUM BLIGHT

Turf Affected:

Kentucky bluegrass, bentgrasses, ryegrasses, tall fescue and creeping red fescue.

Season:

Spring and summer.

Conditions For Development:

High humidity with daytime temperatures ranging from 80 to 95 degrees F.

Early Symptoms:

Scattered light green patches 2 to 6 inches in diameter.

Late Symptoms:

Patches change within 2 days to a dull reddish brown, then tan and finally a light straw color.

FUSARIUM PATCH (Pink Snow Mold)

Turf Affected:

Kentucky bluegrass, bentgrasses, ryegrasses, tall fescue and creeping red fescue.

Season:

Late fall, winter and early spring.

Conditions For Development:

Cold wet weather. High humidity and temperatures from 32 to 45 degrees F. Snow cover provides an ideal environment for the development. Severe outbreaks can also occur during periods of prolonged rainfall and temperatures from 30 to 40 degrees F.

Early Symptoms:

Pale yellow irregularly circular patches.

Late Symptoms:

Affected areas change color to a whitish gray. Individual leaves take on a bleached appearance and feel slimy when wet. The borders may become covered with a dedicated network of "cobwebby" threads which will turn from white to a light pink.

GRAY LEAF SPOT

Turf Affected:

St. Augustinegrass.

Season:

Spring, summer and fall.

Conditions For Development:

Cool wet weather.

Early Symptoms:

Minute brown dots.

Late Symptoms:

Spots enlarge rapidly to form oval spots. The center becomes a depressed gray area with an almost black ring around the edges.

HELMINTHOSPORIUM LEAF SPOT

Turf Affected:

Kentucky bluegrass, bentgrasses, ryegrasses, tall fescue and creeping red fescue.

Season:

Late Spring and summer

Conditions For Development:

Warm wet weather. Most common when temperatures are ranging from 80 to 90 and there are extended periods of rain.

Early Symptoms:

Same as Melting-out.

Late Symptoms:

The infection of the sheath isn't as common as with melting-out. Most of the damage is done to the blade itself. It causes a rapid drying-out of the leaf tissue turning the leaf a light straw color.

MELANOTUS WHITE PATCH

Turf Affected:

Tall fescue.

Season:

Summer.

Conditions For Development:

Most frequently seen if the fescue is under 12 months old or is seeded to heavy.

Early Symptoms:

Circular off white patches.

Late Symptoms:

Patches may mat together and become closely pressed to the soil surface. Restricted to the leaf blades only.

MELTING-OUT

Turf Affected:

Kentucky bluegrass, ryegrasses, and tall fescue.

Season:

Late winter and early spring.

Conditions For Development:

When temperatures are between 55 to 70 degrees F, and extended periods of rainfall or overcast weather.

Early Symptoms:

Minute water-soaked areas.

Late Symptoms:

Areas turn dark pruplish-red, then turn brown and finally a dull white. Damage is mostly seen on the entire sheath of the grass causing the leaves to drop off.

NECROTIC RING SPOT

Turf Affected:

Kentucky bluegrass, bentgrasses, ryegrasses, chewing fescue, tall fescue and creeping red fescue.

Season:

Late winter, spring and fall.

Conditions For Development:

Cool wet spring and fall months.

Early Symptoms:

Irregular patches in shades of red, yellow or tan.

Late Symptoms:

Areas turn tan or brown. Patches are somewhat circular in shape. The thatch may decompose rapidly in the damaged area leaving depressions or a "sunken" area.

NEMATODES

Turf Affected:

All lawn grasses.

Season:

Late spring and summer.

Conditions For Development:

When soil temperatures are in the mid 50's, the population of hatched nematodes increases rapidly.

Early Symptoms:

Infected area begins to look under watered or under fertilized.

Late Symptoms:

Plants will lack overall vigor and will have difficulty with low soil moisture or high temperatures. Growth will be restricted in depth and density

POWDERY MILDEW

Turf Affected:

Kentucky bluegrass, bermudagrass and creeping red fescue.

Season:

Spring and early fall.

Conditions For Development:

Reduced air circulation, high humidity, low light and cool temperatures in the mid 60's F.

Early Symptoms:

Gray-white powdery growth develops on the leaf.

Late Symptoms:

Yellow-green lesions develop on the leaves. These enlarge turning a pale yellow. The entire leaf may be pale yellow in color.

PYTHIUM BLIGHT

Turf Affected:

Kentucky bluegrass, bentgrasses, bermudagrass, ryegrasses, tall fescue and creeping red fescue.

Season:

Spring and summer.

Conditions For Development:

High humidity.

Early Symptoms:

Small irregularly shaped areas that look water logged.

Late Symptoms:

The color fades to a light brown and the leaves shrivel. Areas will often be circular and the leaves will tend to be soft and slimy.

RHIZOCTONIA BLIGHT (Brown Patch)

Turf Affected:

Kentucky bluegrass, bentgrasses, ryegrasses, tall fescue, creeping red fescue, St. Augustine, Bermudagrass and zoysia.

Season:

Winter, spring and summer.

Conditions For Development:

When temperatures are in the low 70's and the leaf remains wet for 36 to 48 hours. If the temperatures are in the 80's the blade may only need to be wet for 8 to 12 hours.

Early Symptoms:

Irregularly blighted areas that are tan or brown. Size ranges from a few inches to several feet in diameter.

Late Symptoms:

Areas enlarge and develop reddish-brown margins and take on a dried out look.

RHIZOCTONIA YELLOW PATCH

Turf Affected:

Kentucky bluegrass, bentgrasses, bermudagrass, tall fescue and zoysia.

Season:

Late winter, spring and fall.

Conditions For Development:

Cool wet weather. Temperature range from 40 to 60 degrees F.

Early Symptoms:

Circles form that turn yellowish-green.

Late Symptoms:

Same as Necrotic Ring spot.

RUST

Turf Affected:

Kentucky bluegrass, bentgrasses, bermudagrass, ryegrasses, tall fescue, creeping red fescue and zoysia.

Season:

Late summer and early fall.

Conditions For Development:

Overcast or cloudy weather with temperatures in the low 70's. High humidity, fog or light rain showers followed by bright sunny days.

Early Symptoms:

Light yellow flecks on the leaves.

Late Symptoms:

The spots enlarge and are parallel with the veins of the leaves. The surface of the leaves rupture and yellow-orange or reddish-brown pustules develop.

SCLEROTINIA DOLLAR SPOT

Turf Affected:

Kentucky bluegrass, bentgrasses, bermudagrass, centipedegrass, creeping red fescue and zoysia.

Season:

Late spring and summer.

Conditions For Development:

When temperatures are between 70 to 80 degrees F. and high humidity.

Early Symptoms:

Yellow-green blotches.

Late Symptoms:

Areas begin to look water-soaked and finally bleach to a straw colored tan with reddish-brown margins.

SLIME MOLDS

Turf Affected:

All lawn grasses.

Season:

Spring, summer and fall.

Conditions For Development:

Prolonged periods of rainy weather.

Early Symptoms:

A creamy white to translucent slimy growth.

Late Symptoms:

The growth changes to distinctive small ash-gray balls. Affected areas will vary from a few inches to several feet in diameter.

SPRING DEAD SPOT

Turf Affected:

Bermudagrass, Kentucky bluegrass, bentgrasses, ryegrasses, tall fescue and chewing fescue.

Season:

Late winter and early spring.

Conditions For Development:

Long dormancy periods. Most severe when temperatures reach the mid 50's.

Early Symptoms:

When turf begins to green-up in the spring, well-defined circular patches become visible.

Late Symptoms:

Leaves take on a bleached straw color. The base of the grass, roots, rhizomes and stolons turn black to brown.

ST. AUGUSTINE DECLINE

Turf Affected:

St. Augustinegrass.

Season:

Any time.

Conditions For Development:

None.

Early Symptoms:

A mild yellow mottling of the blades.

Late Symptoms:

Spots progress a distinct stippling effect. In the second year most of the leaf will be yellow and the third year death of the leaf and stolons will occur.

STRIP SMUT

Turf Affected:

Kentucky bluegrass, bentgrasses, ryegrasses, and tall fescue.

Season:

Late winter and early spring.

Conditions For Development:

Cool air temperatures and bright sunny days 50 to 60 degrees F.

Early Symptoms:

Long yellow-green streaks develop on the leaves.

Late Symptoms:

Streaks become gray. The outer layer of the leaf ruptures and exposes the underlying black masses of spores of the fungus. The leaves split into ribbons and curl from the tips downward.