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  2. Host and Disease Descriptions

Lawn and Turf-Powdery Mildew

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Latest revision: 
March 2024
Image related to Lawn and Turf-Powdery Mildew
White areas on leaves are made up of the mycelium and spores of the fungus.
Photo by Ralph S. Byther

See:

Grass for Seed - Powdery Mildew

Hosts Bluegrass and fescues are most susceptible.

Cause The fungus Blumeria graminis (formerly Erysiphe graminis), which overwinters in infected plants and debris. The powdery appearance is due to masses of spores, which are easily dislodged and carried by air currents. They can infect leaves within 2 hours, produce a new crop of spores in 3 to 4 days, and continue spore production for 1 to 2 weeks. Disease is more prevalent in shaded sites.

Symptoms White-to-gray-brown powdery growth appears on the upper surfaces of leaves and leaf sheaths. Leaves turn yellow to tan to brown and die, usually either killing the plant or weakening and making it more susceptible to winterkill or other diseases.

Cultural control

  • Reduce shade and improve air circulation as much as possible.
  • Use mildew-tolerant cultivars such as Rugby, Glade, Galaxy, A-34, Sydsport, and Baron. These cultivars are not completely resistant, so mix two or more in plantings.
  • Use a moderate, balanced fertilizer. Avoid highly soluble nitrogen fertilizers.
  • Water in morning so turf will dry before night.
  • Mow frequently at the recommended height.

Chemical control Not recommended for home lawns. Alternate or tank-mix products from different groups that have different modes of action. Limit the use of any one group during crop production.

  • Compass 50 WDG is registered for turf, has good activity on powdery mildews, and may be useful here. Group 11 fungicide. 12-hr reentry.
  • Disarm 480 SC at 0.18 to 0.36 fl oz/1,000 sq ft. Group 11 fungicide. 12-hr reentry.
  • Eagle 20 EW at 1.2 fl oz/1,000 sq ft. May produce a growth regulation effect on Kentucky bluegrass. Group 3 fungicide. 24-hr reentry.
  • Fame SC at 0.2 to 0.4 fl oz/1,000 sq ft. Group 11 fungicide. 12-hr reentry.
  • Heritage at 0.2 to 0.4 oz/1,000 sq ft. Group 11 fungicide. 4-hr reentry.
  • Insignia SC at 0.4 to 0.7 fl oz/1,000 sq ft. Do not use with organosilicate adjuvants. Group 11 fungicide. 12-hr reentry.
  • Microthiol Disperss (80% sulfur) at 3 to 10 lb/A. Do not use a spreader-sticker. Group M2 fungicide. 24-hr reentry. O
  • M-Pede at 1 to 2 gal/100 gal water. Good coverage is essential. Do not use within 3 days of applying sulfur. Do not mix with hard water or products that contain chlorothalonil. 12-hr reentry. O
  • Monsoon Turf at 0.6 fl oz/1,000 sq ft. Group 3 fungicide. 12-hr reentry.
  • Propiconazole-based products. Group 3 fungicides.
    • Banner MAXX at 1 to 2 fl oz/1,000 sq ft. 12-hr reentry.
    • PropiMax EC at 0.37 to 0.73 fl oz/1,000 sq ft. 12-hr reentry.
  • Rayora at 0.7 to 1.4 fl oz/1,000 sq ft. Group 3 fungicide. Reentry after sprays have dried.
  • Regalia at 1 to 3 fl oz/1,000 sq ft. Does not benefit from the addition of an adjuvant. Group P5 fungicide. 4-hr reentry. O
  • Tebuzol 3.6F at 0.6 fl oz/1,000 sq ft. Group 3 fungicide. No reentry interval listed.
  • Torque at 0.6 to 1.1 fl oz/1,000 sq ft. Do not mix with growth regulators during hot weather as injury may develop. Group 3 fungicide. 12-hr reentry.
  • Velista at 0.3 to 0.5 oz/1,000 sq ft. Group 7 fungicide. 12-hr reentry.

Combination Fungicides

  • Armada 50 WDG at 0.6 to 1.5 oz/1,000 sq ft. Do not use a silicone-based surfactant. Group 3 + 11 fungicide. 12-hr reentry.
  • Briskway at 0.5 to 1.2 fl oz/1,000 sq ft. Can be used in hot weather. Group 3 + 11 fungicide. Reentry when sprays have dried.
  • Interface at 3 to 5 fl oz/1,000 sq ft. Maintain agitation while spraying. Do not mix with adjuvants. Group 2 + 11 fungicide. 24-hr reentry.
  • Concert at 4.5 to 8.3 fl oz/1,000 sq ft. Do not use on fine fescue turf. Group 3 + M5 fungicide. 12-hr reentry.
  • Headway at 1.5 to 3 fl oz/1,000 sq ft. Do not use with silicone-based surfactants or EC formulations. Group 3 + 11 fungicide. 12-hr reentry.
  • Heritage Action at 0.2 to 0.4 oz/1,000 sq ft. Group 11 + P1 fungicide. 12-hr reentry.
  • Honor at 0.55 to 1.1 oz/1,000 sq ft. Do not use with organosilicone-based adjuvants. Group 7 + 11 fungicide. Golf course turf only.
  • Lexicon at 0.34 to 0.47 fl oz/1,000 sq ft. Group 7 + 11 fungicide. 12-hr reentry.
  • Navicon at 0.7 to 0.85 fl oz/1,000 sq ft. Group 3 + 11 fungicide. 12-hr reentry.
  • Pillar G at 3 lb/1,000 sq ft. Group 3 + 11 fungicide. 12-hr reentry.
  • Renown at 2.5 to 4.5 fl oz/1,000 sq ft. Group M5 + 11 fungicide. 12-hr reentry.

Biological control

  • Rhapsody at 2 to 10 fl oz/1,000 sq ft. Active ingredient is a protein from Bacillus subtilis strain QST 713. Efficacy in the Pacific Northwest is unknown. 4-hr reentry. O

Reference Smiley, R.W., Dernoeden P.H., and Clarke, B.B. 2005. Compendium of Turfgrass Diseases. 3rd edition. St. Paul, MN: APS Press.