Research & Development Field Report – 12th Edition

The PBI-Gordon Research & Development Team is pleased to present the 12th 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 OVERVIEW

As we prepare for the 2026 season, the primary variable remains the widespread cold and snowy weather experienced across much of the country this winter. While it is too early to determine the full extent of the environmental impact, R&D recommends a “wait and see” approach combined with proactive monitoring as the snow recedes.

• Turf Assessment: As we enter spring, turf managers should be prepared to assess the impact of prolonged snow cover and sub-freezing temperatures. Potential issues could range from desiccation to varying degrees of winterkill, particularly in the transition zone.
• Soil Temperature Monitoring: Because the ground may remain colder longer due to snow insulation, relying on 2-inch soil temperature probes will be more accurate for timing applications than following the calendar alone.
• Saturated Conditions: Be mindful that significant snowmelt can lead to saturated soil profiles, which may influence early-season root health and the timing of equipment traffic.
• Check your spray water quality: Most of what comes out of a spray tank is not a fungicide, herbicide, or insecticide – it’s water. Water quality should be tested twice a year (i.e. spring and fall) using a reputable lab. Check pH, carbonates and bicarbonates, as well as divalent cations such as calcium, magnesium, sodium, iron, and aluminum. These can affect product performance by binding to the active ingredients if the mix sits in the tank for more than a short period of time.

DISEASES

• Microdochium Patch (Pink Snow Mold)
  With the lingering snow cover especially in the Northeast, Microdochium patch may persist well into the spring.
  • If cool, rainy conditions continue after snowmelt, apply fungicides when symptoms are first observed.
  • Incorporating multiple modes of action is a highly effective strategy. For example, combinations of strobilurins, DMI’s, and a contact fungicide (especially chlorothalonil or fluazinam) can provide top-tier efficacy and help manage resistance risk.
  • Applications to control the disease prior to turf actively growing will not reduce symptoms, but will aid in further spread of the pathogen.
• Large Patch
  In warm-season turf, especially Zoysiagrass and St. Augustinegrass, large patch is frequently found in the spring when rainy, humid conditions persist or turf is overirrigated.
  • Preventive fungicide applications are desirable.
  • SDHI fungicides, such as flutalonil (Pedigree Fungicide SC) and penthiopyrad provide excellent control and have great turf safety.
  • Combination products, especially those containing azoxystrobin, are also effective.
• Root Pathogen Preparation
  

  As soil begins to warm, the focus should shift to the root zone.

  • Fairy Ring: Start monitoring for 55°F soil temperatures. A cornerstone program includes two applications of Pedigree Fungicide SC at 3.25 fl. oz./1,000 sq. ft. spaced 28 days apart. Incorporating a wetting agent and ensuring at least 1/4″ of irrigation immediately following application is vital for success. Early applications of Pedigree can also provide control of early spring diseases like Yellow Patch and Waitea patch.

  • Take-all root rot: A programmatic approach to take-all root rot should include several preventive applications in the late summer and early fall. Spring applications should be made where the disease is persistent or if symptoms begin to appear. Preformulated products with a QoI + DMI are the most effective. Several spring applications may be required, and ensure products are watered-in with post application irrigation.

  • Pythium Root Rot: It’s really never too early to start your Pythium root rot program, especially if you have a history of the disease. 2” soil temperatures above 60°F are the ideal time to initiate program sprays. Rotating Segway® Fungicide SC (0.9 fl. oz./1,000 sq. ft.) with picarbutrazox every 14 days remains a top-performing strategy in our trials.

WEEDS – PRE-EMERGENT TIMING & STRATEGIES

1. Pre-Emergent Crabgrass StrategyTiming is dictated by soil temperature: consistently 50°F for 4–5 days.
   • Primary Product: Bensumec™ 4 LF Pre-Emergent Grass & Weed Herbicide
     • Greens/Tees: 2 apps per year –
       • 6 fl. oz./1,000 followed by 6 fl. oz./1,000 OR 9 fl. oz./1,000 followed by 9 fl. oz./1,000
     • If crabgrass germination has already occurred prior to your initial pre-emerge application,
       consider Dithiopyr (warm-season and cool-season turf) or tank-mix Katana® Turf Herbicide (for warm-season turf only, such as bermuda/zoysia) with your PRE to hit early-stage crabgrass, broadleaf weeds and nutsedge/kyllinga species simultaneously.
2. Pre-Emergent Goosegrass StrategyGoosegrass emerges later—typically 4–6 weeks after crabgrass—once soil temps hit 60°F.
   • Effective actives: Oxadiazon and Indaziflam are the heavy hitters for effective pre-emergent goosegrass control.
3. Grassy Weed Escapes (Crabgrass & Goosegrass)Even with a pre-emergent (PRE) program, “break throughs” happen.
   • Crabgrass: Q4® Plus Turf Herbicide for early-POST clean-up. Adding a surfactant, especially MSO, will boost efficacy. May be used in both cool-season and warm-season turf (check label for turf tolerance).
   • Goosegrass: Use SpeedZone® EW Broadleaf Herbicide for Turf alone or SpeedZone® EW (4 pt./A) + Topramezone (0.25 fl. oz./A). Either of these treatments will also handle any lingering winter broadleaf weeds as well as any summer broadleaf weeds that have emerged such as prostrate knotweed.
4. Winter Annuals & Spring Transition Safety
   The biggest risk right now is injury to warm-season turf, especially St. Augustine and Centipede,
   during spring green-up.
   • Temperature: In cooler weather, Ester formulations (i.e.
     SpeedZone EW, SpeedZone® Southern EW Broadleaf Herbicide for Turf, TZone™ SE Broadleaf Herbicide for Tough Weeds, or PowerZone® Broadleaf Herbicide for Turf) are more effective than Amine formulations.
   • For sensitive warm-season turfgrass species consider using the following products to avoid turf injury
     during transition:

      

     • Avenue™ South Broadleaf Herbicide
       
     • SpeedZone Southern EW
       
     • Trimec® Southern Broadleaf Herbicide for Sensitive Grasses
       
     • Aethon® Herbicide SL for Turfgrass (non-2,4-D)
5. Nutsedge & Kyllinga Control
   Sedges and Kyllingas are currently or beginning to emerge, especially in thin, wet areas. Because they emerge from seed, tubers and rhizomes, early post-emergent (POST) applications are key, especially before new rhizomes and tubers begin to form. Soil temperatures (°F) when various species begin to emerge.
   • Yellow Nutsedge – Mid 50’s, Kyllinga species – 60’s, Purple Nutsedge – Mid 60’s
     • Top Recommendation: Arkon™ Herbicide Liquid. Use two applications at 1.2 fl. oz./1,000 sq. ft. spaced 6 weeks apart. It is safe across both warm and cool-season turf species (including golf course putting greens).
     • Granular Option: Vexis® Herbicide Granular. Apply at 4 lb./1,000 sq. ft. (two applications, 6 weeks apart).
     • Adequate soil moisture at time of application is essential to achieve best results.
6. Broadleaf Weed ManagementNow is the time to begin thinking about summer broadleaf weed control as they will be or have already been emerging.
   • Solution: SpeedZone EW, TZone SE, Surge® Broadleaf Herbicide for Turf or Q4 Plus for both broadleaf weeds as well as any emerged crabgrass that may have been missed by the preemergent application.
   • Tough/perennial weeds like Virginia buttonweed or ground ivy may require two applications.
7. Bermudagrass Winter Kill
   The “perfect storm” for Bermudagrass winterkill occurred in the Southeast and Transition Zone this year as a result of specific environmental stressors, including a combination of dehydration and extreme temperature fluctuations during dormancy, with many areas experiencing less than normal rainfall.
   • The Role of the “Winter Drought”
     Even in a brown, dormant state, the rhizomes and stolons (the plant’s survival structures) must remain hydrated.
     • Desiccation: When the soil is severely dry, the plant loses moisture to the air. If the crown of the plant dries out completely, it dies.
     • Reduced Insulation: Dry soil has more air pockets than moist soil. Moist soil holds heat better and acts as an insulator; bone-dry soil allows freezing air to penetrate deeper and faster, reaching the sensitive root system.
   • The Late Winter “Cold Snap”The timing of the cold temperatures in late January and early February was particularly hazardous.
     • De-acclimation: If there were any unseasonably warm days leading up to the freeze, the Bermudagrass may have begun “waking up” (metabolic activity), making it far more susceptible to cellular rupture when the temperature plummeted.
     • Crown Hydration: Rapid freezing after a period of high moisture (or even during extreme drought) can cause ice crystals to form within the plant cells, physically shattering the cell walls of the crown.
   • High-Risk Zones: Slopes and ShadeIf you are scouting your turf, focus your attention on these specific micro-climates:
     • North-Facing Slopes: These areas receive the least amount of direct sunlight during the winter. They stay colder longer and are the last to “green up,” making them more prone to extended periods of freezing.
     • Shaded Areas: Shade from trees or structures further reduces the soil temperature. Bermudagrass in the shade is already under “light stress” during the summer, meaning it enters winter with lower carbohydrate reserves (energy) to fight off winter kill.
     • High-Traffic Areas: Compacted soil in walkways or cart paths limits oxygen and increases the likelihood of winter kill, as the stressed plants have less resilience.
   • What to Look For
     As temperatures rise, look for delayed green-up. If large patches remain brown and brittle while the
     surrounding grass turns green, take a sample and look at the stolons and rhizomes.
     • If the stolons and rhizomes are dark, shriveled, and brittle, it is likely winter kill.
     • If the stolons and rhizomes are firm and white/off-white inside, the plant may just be coming out of dormancy slower.

     While the focus has been on bermudagrass, it’s important to note that other warm-season varieties like St. Augustinegrass and centipedegrass are often even more vulnerable to winter kill.

     The primary reason for this increased risk lies in their biology:

     • Lack of rhizomes: Unlike bermudagrass, which produces both stolons (above-ground runners) and rhizomes (below-ground stems), St. Augustine and centipede rely solely on stolons for growth and recovery.
     • Exposure: Because their “reproductive” hardware stays above the soil surface, it lacks the natural insulation that the soil provides to bermudagrass rhizomes.
     • Lower cold tolerance: These species are generally less cold hardy than bermudagrass to begin with. When a hard freeze hits, they don’t have a “backup” underground energy reserve to push new growth if the surface stolons are damaged.

     In these species, look for stolons that have turned mushy, dark brown, or gray. If the runners are brittle and easily pull away from the soil, the plant has likely suffered significant damage and may require sodding or plugging to recover.