You Are Here: Management Updates 2007 Archive June 12, 2007

Date: June 12, 2007
Category: Diseases
Subject: Pink Snow Mold, Necrotic Ring Spot

Moderate temperatures and adequate rainfall during the first weeks of June have resulted in good conditions for turfgrass growth. Outside of several cases of pink snow mold from Northern New England, the most prevalent turfgrass disease arriving at the UMass Extension Plant Diagnostic Lab has been necrotic ring spot, which has been seen on golf courses (Poa annua), athletic fields (P. pratensis), and utility grass (Festuca rubra).

Necrotic ring spot is caused by Ophiosphaerella korrae, an ectotrophic root infecting fungus which causes a patch disease primarily on Poa species. The pathogen is active in the cool, wet weather of the spring and fall; symptom expression of wilt and straw colored patches may also occur in the summer stress period. Infection centers that develop in the fall may persist through winter and into early spring. Recovery is slow. Patches often have a frog-eye appearance.

Management of necrotic ring spot includes cultural measures such as the avoidance of drought stress by light, daily irrigation and the use of slow release nitrogen fertilizers in the summer stress period. Avoid nutrient deficiencies and provide adequate and balanced fertility, particularly nitrogen, potassium, and phosphorous as determined by soil or foliar tissue tests. Overseeding infected turf with Lolium perenne, more resistant cultivars of Poa pratensis, or Agrostis species will limit symptom expression and disease severity.

Biological management options include LawnRestore™ or TurfRestore™ which contain both beneficial microorganisms and food to stimulate the natural microflora. Aerifying, improving drainage, and reducing compaction aid in disease control. Thiophanate methyl fungicides (Cleary’s 3336™, FungoFlo™) can be applied curatively in early to mid-spring, being sure to thoroughly irrigate turf first as these fungicides only move upwards (acropetal penetrants). Propiconazole (Banner MAXX™), fenarimol (Rubigan™), and iprodione (Chipco 26019™) work best when applied preventively.

Submitted by: M. Bess Dicklow

DISCLAIMER - As always, it is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. Different states have different regulations as well. Trade names of materials are provided for informational purposes only and do not substitute for a thorough and careful reading of the label and application according to label instructions. The author and the University of Massachusetts are not liable for any consequences of any pesticide recommendations. Mention of any trade name is not to be considered endorsement of a product.

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