EXAM 1 PLSC 401

Diseases To Know:

Cool Season

• Dollar Spot

  • Clarireedia jacksonii

  • Symptoms

    • Small Sunken Circles

    • Tan/ Reddish Brown Leaf Lesions

    • Hourglass shaped lesions

  • Signs

    • Fungal Mycelium From Morning Dew

  • Favorable Conditions

    • 59-86°F

    • Late Spring to Late Fall

    • War, Humid Days, Cool Nights, Heavy Dew

    • Low Nitrogen

• Brown Patch

  • Rhizoctonia solani

  • Symptoms

    • Patch appearance (brown or yellow)

    • Leaf lesions are tan with dark brown edges

  • Signs

    • Mycelium in humid conditions

    • Smoke rings

  • Favorable Conditions

    • High leaf wetness

    • Hot, rainy, humid weather

    • 70-90°F

    • Poorly Drained Soil

• Pythium Blight

  • Pythium aphanidermatum

  • Symptoms

    • Circular Spots

    • Oily lesions

  • Signs

    • Coenocytic mycelia

  • Favorable Conditions

    • Hot, Humid, Rainy weather

    • 86-95°F

    • High Humidity for 14+ hours

    • High nitrogen and alkaline soils

• Anthracnose

  • Colletotrichum cereale

  • Symptoms

    • Yellow or reddish leaf discoloration

    • Loss of shoot density

    • Water soaked or black rot on crown

    • Thinning or complete die off of large areas

  • Signs

    • Acervuli, small dark elongated structures in infected tissues

    • Setae, which are long, dark brown or black septate spines

    • Crescent shape conidia

    • Appressoria and hyphopodia

  • Favorable conditions

    • High humidity, overcast weather, and excessive moisture in the leaf canopy

    • Stress driven disease: low mowing height, low fertility, drought stress, dry soils, and extreme temperatures

    • Increased under NPK deficiencies

    • Verti cutting may worsen disease

• Gray Leaf Spot

  • Pyricularia oryzae

  • Symptoms

    • Small water soaked lesions

    • Rapid expansion that can look similar to brown patch

  • Signs

    • Grayish masses of conidia

    • Gray/olive colored conidiophores

  • Favorable conditions

    • 82-90°F

    • High humidity with 9-10 hours of leaf wetness

    • Primarily in new establishment 

    • High nitrogen fertility

• Red Thread

  • Laetisaria fuciformis

  • Symptoms

    • Circular or irregular patches of straw brown turf

    • Necrosis typically progress from leaf tip to the base

  • Signs

    • Pinkish to red-orange mycelium and sclerotia

  • Favorable conditions

    • Spring and fall

    • 59-77°F

    • Nitrogen Deficiency

    • Moisture Saturated Air

• Leaf Spot

• Rust

  • Puccinia coronate

  • Symptoms

    • Vary with each type but include yellow to orange patches

  • Signs

    • Orange, brownish, yellow, spores, masses that easily come off

    • Teliospores, black overwintering spores

  • Favorable conditions

    • 50-86°F depending on the rust type

    • Leaf moisture is required for rust spores

    • Worse under dry conditions

    • Stress: Drought, nutrient deficiency, low mowing height, shade, and compaction

• Powdery Mildew

  • Blumeria grannis

  • Symptoms

    • Yellowing of the leaves

    • Tan or brown patches as infected areas die

  • Signs 

    • Powdery white to grayish fungal growth

    • Mycelium and cleistothecia

  • Favorable conditions

    • Cool, Humid, and cloudy weather

    • Shaded areas with limited air circulation and lack of sunlight

    • Nitrogen fertility

• Algae

  • Cyanobacteria

  • Signs and Symptoms

    • Slimy appearance

    • Green or bluish green mats

    • Indirect injury

    • Strands of algae around the plant

  • Favorable conditions

    • Warm and humid

    • Heavy rains

    • Poor drainage

    • Low mowing heights

• Take All Patch

  • Gaeumannomyces avenae

  • Symptoms

    • Small circular patches

    • Light brown or reddish colors

    • Worse after hot dry weather in late summer

  • Signs

    • Ectotrophic hyphae on roots

    • Dark brown perithecia in leaf sheaths around crowns

  • Favorable conditions

    • Cool, wet weather in fall or spring followed by hot dry conditions

    • Soil with light texture

    • Low organic matter

    • pH above 6.5

    • Low or unbalanced fertility

• Summer Patch

  • Magnaporthispsis poae

  • Symptoms

    • Typical in turfgrass that is older

    • Orange to reddish brown patches

  • Signs

    • Dark brown to black ectotrophic hyphae

    • Vascular discoloration and cortical rot

    • No perithecia

  • Favorable conditions

    • Infection begins in the spring when rootzone gets to 64-70° F

    • Air temps of 77-86°F

    • Wet soil conditions

    • Turf stresses: Soil compaction, drought, low fertility, low mowing height, high soil pH, excessive nitrogen

• Fairy Ring

  • Basidomycetes

  • Symptoms and Signs

    • Rings, semicircles, or arcs of dead grass

    • Mushrooms or puffballs

    • Thatch/ soil with mushroom oder

    • Extremely dry soil due to water repellency

  • Favorable conditions

    • Can occur throughout the season

    • Low fertility

    • Low soil moisture

    • Under fertilized turf

    • Thick thatch layers

    • Sandy soil