Summer Disease Control in Cool-season Lawns

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Summer disease control in cool-season turf can be difficult, especially in the transition zone where cool-season grasses are not as well adapted. Cultural practices are critical for disease management but often fungicides are required for the toughest diseases.

  • Establish the right species:
    • Tall fescue is the best adapted cool-season grass in the transition zone and farther north
    • Kentucky bluegrass is well-adapted throughout the northern cool-season region
    • Perennial ryegrass is well adapted in cooler regions with limited heat and humidity during the summer
    • Fine leaf fescues are well adapted to drier, cooler areas like the high desert and are usually not susceptible to many diseases in this growing environment
  • Basic cultural practices for cool-season grasses:
    • Limit irrigation, erring on the dry side rather than on the saturated side. Deep and infrequent irrigation is the rule
    • Mow frequently at 3” or higher – lower mowing height reduces photosynthetic area and adds stress during the summer. Mow often enough to not remove more than 1/3 of the leaf blade, which might be every 3-4 days in spring and 7-14 days or more during heat of summer
    • Ensure adequate nutrition throughout the season, but apply most N fertilizer in the fall, with lesser amounts in spring and summer
    • Aerify as needed to minimize compaction, improve water movement, and reduce thatch
  • Primary diseases
    • Brown patch- can be extremely damaging in tall fescue throughout much of the summer in the transition zone, especially with frequent rain, high humidity, and high temperatures
    • Dollar spot – affects perennial ryegrass and Kentucky bluegrass from spring through fall in high humidity and generally slower growing turf
    • Fairy ring – can affect all cool-season grasses starting in spring with symptoms typically peaking in mid to late summer
    • Summer patch/necrotic ring spot – root infecting diseases of Kentucky bluegrass. Infect roots primarily in spring and/or fall, with symptoms appearing in dry weather of summer
  • Effective fungicide use:
    • Read the label – few fungicides are labelled for residential use
    • History repeats itself – lawns with historical problems of diseases like fairy ring and summer patch will likely have symptoms every year
    • Fairy ring, summer patch and necrotic ring spot - preventive applications are required starting at 2” soil temperature average of 55-65°F followed by watering in with ¼ inch of water
    • Brown patch – usually can be controlled early curative, but air temperature + humidity >150 in the forecast is when to start applications
    • Dollar spot – can usually be managed culturally with proper irrigation and fertilization, but can be controlled curatively with a fungicide once symptoms are seen
  • Bayer’s lawn disease solution: Armada®
    • Can be applied to all cool-season species as well as most landscape trees and ornamentals
    • Controls 17 different turf diseases and a multitude of ornamental plant diseases
    • Guaranteed Bayer programs with Armada include fairy ring
  • Need more info? – see the Bayer Solutions Guides for more information, and contact your Bayer area sales manager if you need assistance.

brown patch tall fescue crop 

Brown patch affects tall fescue in the high heat and humidity of summer and can be extremely damaging in the transition zone (Bayer).

summer patch 

Summer patch can be extremely damaging on Kentucky bluegrass, especially that growing on poor soil. Fungicide applications should start at 2-inch soil temperatures of 65oF (Bayer)

  Dollar Spot Solutions Guide
  Brown Patch Solutions Guide
  Fairy Ring Solutions Guide
  Summer Patch Solutions Guide
Rob Golembiewski

by Rob Golembiewski , Ph.D., Green Solutions Team Specialist

Monday, May 24, 2021

Zac Reicher

by Zac Reicher , Ph.D., Green Solutions Team Specialist

Monday, May 24, 2021