Research & Development Field Report – 11th Edition

The PBI-Gordon Research & Development Team is pleased to present the Eleventh Edition of the R&D Field Report. This report contains scientific information to support the important work underway by our agronomic partners, distribution representatives, and end-users. Our intent is to provide useful, research-based information prior to the seasonal emergence of pests. You can look for updated R&D Field Reports on a quarterly basis.

GENERAL OBSERVATIONS

• Endless rain, high temperatures, and high humidity caused significant thinning and loss of turf where cool-season grass was grown, particularly in the Midwest, Northeast, and Mid-Atlantic
• With lots of moisture and thinning turf, areas not treated with a pre-emergent (or treated with single applications at lower rates) have seen significant infestations of crabgrass
• Goosegrass has been easy to find in many locations, especially along the East Coast
• Yellow nutsedge and Kyllinga are prevalent in areas where saturated soils have persisted
• Conditions in cool-season turf were prime for brown patch, Pythium blight, and dollar spot activity – most notably in higher cut turf where preventive applications are not widely applied
• Saturated soils have resulted in significant Pythium root rot activity, and if rain continues into the fall, root infecting pathogens causing diseases such as spring dead spot or Take-all root rot warrant preventive applications

WEEDS

• It’s Poa Time:
  • Herbicide programs for Poa control in bermudagrass and Zoysiagrass should include a combination of PRE and POST herbicides applied multiple times.
  • Research has shown Katana® Turf Herbicide can control provide season-long Poa control >90% when mixed with simazine and any PRE herbicide (e.g., indaziflam, prodiamine, and pronamide) and applied twice in fall and winter.
  • Katana® and Bensumec™ 4LF Pre-Emergent Grass and Weed Herbicide can be used in a similar manner on ultradwarf bermudagrass putting greens.
  • Bensumec™ works best and is safest on ultradwarf bermudagrass when applied in rotation with other residual herbicides. Any tank-mixtures with Bensumec should include the lowest labeled Bensumec rate and not re-applied within four weeks.
  • Initial application should be made at an early-POST timing (October-December) with the follow-up application 2 months later. Application intervals are shorter for bermuda putting greens.
• Late summer sedge and Kyllinga control
  • Arkon™ Herbicide Liquid applied at 1.7 fl. oz./1,000 sq. ft. will effectively reduce sedge populations.
  • In areas where Kyllinga persists later in the fall, split applications at 1.25 fl. oz./1,000 sq. ft. should be applied 6 weeks apart.
• Fall weed control
  • Fall broadleaf herbicide applications aid in long-term control of perennial and biennial broadleaf weeds such as dandelion, thistles, wild violets, and clover. These weeds have underground structures facilitating year-to-year survival and herbicides move down into those structures with cooler weather.
  • Furthermore, fall applications may provide some control of early-germinating winter annual weeds such as chickweed and henbit. Products such as SpeedZone® EW Broadleaf Herbicide for Turf and TZone™ SE Broadleaf Herbicide for Tough Weeds applied prior to first frost are ideal for fall applications.
• Fixing areas with lost turf – herbicides for establishment/seeding
  • Summer heat and stress may eventually kill turfgrass and those voids may need to be reseeded or resodded/sprigged. However, prior to optimal seeding weather, weeds may likely invade those voids left by dead turfgrass.
  • Herbicide selection around turfgrass establishment is important to protect the new seedlings and roots. Below is a summary table of herbicides that can be safely used around turfgrass establishment.

DISEASES

• Preparation for tropical systems:
  • Pythium blight
    • Apply Segway® preventively at 0.6 fl. oz./1,000 sq. ft.; rotate with propamocarb
    • Union® Fungicide SC is ideal for control of both Pythium Blight and leaf spots
  • Gray leaf spot
    • Preventive applications should be made every 14 days
    • Prothioconazole and thiophanate-methyl provide the best control as single actives
    • Rotating these actives and tank-mixing with chlorothalonil or fluoxastrobin is suggested
  • Bipolaris leaf spot
    • Preventive applications with iprodione, chlorothalonil, or azoxystrobin should be applied
    • Tank-mixing these active ingredients will enhance efficacy
  • Spring dead spot (SDS)
    • Kabuto® Fungicide SC is the premier fungicide for control of spring dead spot (Golf/commercial)
      • >95% control is achieved with a single application of 3.2 fl. oz./1,000 sq. ft.
        • Application must be applied when 2” soil temperature is between 55-65°F
        • Immediate post-application irrigation (>1/8”) is critical
      • >95% control is achieved with two applications 1.0-1.6 fl. oz./1,000 sq. ft.
        • First application when 2” soil temperature is below 70°F
        • Second application ~21 days after treatment (before 2” soil temp is < 60°F)
        • Immediate post-application irrigation (>1/8”) is critical
      • PBI-Gordon offers a Fungicide Assurance program for spring dead spot control on greens
        Contact your PBI-Gordon representative for more information.
  • Take-all root rot (TARR)
    • Tank-mixes containing azoxystrobin and a DMI fungicide (such as mefentrifluconazole or prothioconazole) should be the cornerstone of a preventive program
      • Immediate post-application irrigation (>1/8”) is critical

FORMULATION CHEMISTRY

• The active ingredient in Katana is flazasulfuron, which is a sulfonylurea class of chemistry. Sulfonylureas once added to water will begin to degrade at a rate that is dependent upon the spray tank pH. Know the pH of the water you will be using with sulfonylureas. Chemical decomposition of sulfonylureas is slower with pH levels from neutral (pH = 7) and basic (pH above 7). At acidic pH levels (below pH = 7), the decomposition can increase by two-fold. Only prepare the amount of spray volume you anticipate using for that day.
• Arkon contains the active ingredient pyrimisulfan, which is very tolerant to broad ranges of pH in the spray tank. Because of the robust nature of this molecule, Arkon makes an exceptional spray tank partner. Q4® Plus Turf Herbicide for Grassy & Broadleaf Weeds + Arkon is a very compatible combination in the spray tank and broadens the weed control spectrum.
• Many of the commercially available fungicides are suspension concentrates (SCs). These formulations are comprised of very fine solids (active ingredients) suspended in a water-based matrix. Once added to a static spray tank, settling can occur. It is suggested to have moderate agitation to maintain spray tank homogeneity with all suspension concentrates. This includes all suspension concentrates (herbicides and insecticides).