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Extension > Garden > Diagnose a problem > What's wrong with my plant? > Turf > Distinct circular patches, rings, or arcs

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Turf > Distinct circular patches, rings, or arcs

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  • Image: pink snow mold 1
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Pink Snow Mold
Microdochium nivale

  • Round patches of tan to gray matted down grass, 2 to 8 inches wide
  • Patches appear pale pink in the sun, and may have a gray border
  • Many patches may grow together to create large dead areas in the lawn
  • Disease only occurs in wet conditions at close to freezing temperatures (early spring is most common)
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  • Image: gray snow mold 1
  • Image: gray snow mold 2
  • Image: gray snow mold 3

Gray Snow Mold
Typhula sp.

  • Round gray patches of matted down grass, 1 inch to 3 feet wide
  • Patches may appear silvery-gray and brittle when dry
  • In wet conditions cobweb-like fungal growth can be seen on the patches
  • Tan to dark brown, hard oval to round ball the size of bee-bees occur on infected grass blades
  • Many patches may grow together to create a large dead area in lawn
  • Disease only occurs in wet conditions at close to freezing temperatures (early spring is most common)
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  • Image: patch 1
  • Image: patch 2
  • Image: patch 3

Patch diseases
Rhizoctonia sp., Magnaporthe sp. and Opioshpaerella

  • Patches of tan upright dead grass in round patches, rings or arcs
  • Patches start out 2 to 4 inches wide, but can grow up to 2 to 3 feet wide
  • No spots on leaves
  • If dug up, roots and crowns of grass plants are black, roots may be rotted, short and thin
  • Symptoms commonly appear during a hot, dry period following cool, wet weather
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  • Image: fairy rings 1
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Fairy Rings
Many different saprophytic fungi

  • Dark green rings or arcs in lawn, and inner ring of brown grass may or may not be present
  • Grass in the ring or arc may be taller than surrounding grass
  • Mushrooms may be present in rings or arcs during wet weather
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  • Image: dog spot 1
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Dog spots

  • Common in lawn areas visited by dogs
  • Typically circular areas of dead grass less than 12 inches across; several patches close together may form larger, irregular dead areas
  • Dead grass plants initially tan to light brown in color
  • Grass plants on the perimeter of the affected area are darker green and taller than the rest of the lawn
  • If spots are watered thoroughly, followed by reseeding, new grass plants usually germinate and successfully fill the original dead area
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  • Image: herbicide 1
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Non-selective herbicide injury
Trade names: Round-up, Kleen-up, among many others

  • Occurs in areas where non-selective herbicides (kill all green plants) have been applied
  • Irregular to round patches of dry, tan grass; pattern of damage follows pattern of herbicide application
  • Affected grass plants are initially light tan to straw-colored, later turning dark brown
  • Usually a distinct boundary between affected and healthy plants
  • Weeds or other plants in the area are brown, dried up or dead as a result of applying these herbicides
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  • Image: dollar spot 1
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Dollar Spot
Sclerotinia homeocarpa

  • Randomly scattered tan to gray round dead patches, 2 to 6 inches wide
  • Cobweb like fungal growth on infected grass blades during cool wet periods like early morning
  • Leaf blades have dry, tan sections with a rusty-brown border, early leaf infections may be a dry, tan oval with a rusty brown border
  • Many small patches may grow together to create larger areas of thin, tan grass

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