Research & Development Field Report – 10th Edition

The PBI-Gordon Research & Development Team is pleased to present the Tenth Edition of the R&D Field Report. This report contains scientifc 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 throughout 2025.

WEEDS

• Post-Emergent Nutsedges and Kyllinga Control:
• Nutsedges and kyllinga are emerging or beginning to emerge, particularly in areas that are wet and thin. These weeds grow underground tubers and/or rhizomes, requiring early post-emergence (POST) applications for effective control. Arkon™ Herbicide Liquid offers season-long control, with two applications at 1.25 oz./1,000 sq. ft. spaced 6 weeks apart being the most consistent method. Arkon™ can be used safely across most cool-season and warm-season turfgrass species and is labeled for use on greens. Arkon may be tank mixed with most herbicides for increased weed control spectrum.
• Other options for nutsedge and kyllinga control include:
• Aethon^® Herbicide SL for Turfgrass:
• Active Ingredients: Pyrimisulfan and Penoxsulam
• Herbicide for controlling broadleaf, sedge, and kyllinga in warm-season turfgrass; ideal for situations where broadcast 2,4-D applications have already been utilized, and an alternative solution is needed.
• Vexis^® Herbicide Granular
• Active Ingredient: Pyrimisulfan
• Labeled for many turfgrass species.
• Best results are from early-POST applications, which maximize residual control.
• Apply 4 lb./1,000 sq. ft., with two applications spaced 6 weeks apart.
• Soil moisture is essential for the herbicide’s effectiveness, so ensure there’s enough moisture for both turfgrass and weeds to grow.
• Scouting is key to timing the early-POST application accurately.
• Katana^® Turf Herbicide:
• Active Ingredient: Flazasulfuron
• Specifically effective on bermudagrass putting greens.
• For kyllinga, apply 1.5 oz./A with a non-ionic surfactant (NIS).
• For nutsedge, apply 2.5 – 3 oz./A with NIS.
• Post-Emergent Broadleaf Control:
• Target any remaining winter annual weeds.
• Now is the time to begin controlling summer weeds. Weeds are easier to control when they are small and immature.
• Herbicide options:
• SpeedZone^® EW Broadleaf Herbicide for Turf
• TZone™ SE Broadleaf Herbicide for Tough Weeds
• Avenue™ South Broadleaf Herbicide
• Surge^® Broadleaf Herbicide for Turf
• Aethon^® Herbicide SL for Turfgrass
• Hard-to-Control weeds such as Virginia buttonweed, doveweed, Oxalis, wild violet, and ground ivy often require two herbicide applications for complete control.
• Take care when applying during turfgrass green-up or transition periods, as herbicide applications can delay full spring green-up.
• Post-Emergent Crabgrass and Goosegrass Control:
• Pre-emergent herbicides (PREs) can be effective for up to 90+ days, but breakthroughs can happen. Sequential applications may be needed to provide season-long control.
• For any crabgrass escapes, early-POST applications with Q4^® Plus Turf Herbicide for Grassy & Broadleaf Weeds will help clean up any escapes, along with control for broadleaf weeds and nutsedges.
• Early application is key for best control, especially since crabgrass is more difficult to control when it reaches a more mature growth stage.
• Adding NIS or methylated seed oil (MSO) surfactants can enhance control.
• Be cautious of slight bermudagrass injury when applying.
• Katana^® can also be used on bermudagrass putting greens, with two applications at 2.5 – 3.0 oz./A + NIS, with a third application potentially necessary depending on crabgrass pressure.
• For any goosegrass escapes early-POST Applications with SpeedZone can help clean up any escapes, along with broadleaf weed control. The addition of Topramezone at 0.25 oz./A can offer increased efficacy and weed spectrum
• Key Considerations:
• Most pre-emergent herbicides can provide both grassy and broadleaf weed control, their forte is on grassy weeds. Keep in mind that you may not be able to see these weeds in the early season as they are hidden underneath the turf canopy. Early control is crucial as immature weeds are more susceptible to herbicides.
• Applying herbicides early in the season maximizes effectiveness when the weeds are small and immature and are more susceptible to herbicides.
• Soil moisture is critical for herbicide efficacy.
• Avoid herbicide applications during the green-up phase to prevent delays in spring recovery.

DISEASES

• Foliar Disease Management:
  As cool-season turf transitions into early summer, foliar diseases driven by spring moisture give way to root and crown pathogens activated by rising soil temperatures. Successful disease prevention hinges on timely intervention, cultural control, and rotating effective chemistries based on environmental conditions and turf history.
• Target Soil Temperatures for Preventive Applications (2″ depth; 3–5 day rolling average):
• 55°F: Fairy ring, Waitea patch
• 60–65°F: Pythium root rot, summer patch, anthracnose, dollar spot
• Foliar Diseases: Leaf Spot, Melting Out, Red Thread, and Dollar Spot:
• Leaf spot and melting out, caused by Drechslera and Bipolaris spp.,are common in Kentucky bluegrass and perennial ryegrass during cool, wet conditions—especially in shaded or nutrient-deficient turf.
• Red thread is typically cosmetic but persistent in low-input turf, producing visible pink or red sclerotia on leaf tips.
• Dollar spot often becomes active as soil temperatures climb into the low 60s, particularly on closely mown turf, and may persist through the growing season.
• Cultural Control:
• Apply 0.2–0.25 lb. N/1,000 sq. ft. using quick-release sources.
• Mow when dry with sharp blades; prune for improved airflow and reduced leaf wetness.
• Reduce thatch and compaction through aerification and topdressing.
• Fungicide Options:
• Tekken^® Broad Spectrum Fungicide: 3.0 fl. oz./1,000 sq. ft.
• Pedigree Fungicide SC: 2.2 fl. oz./1,000 sq. ft. for red thread
• Tank mixes with chlorothalonil, iprodione, or fluazinam can expand control spectrum.
• For dollar spot, use the Smith-Kerns Dollar Spot Prediction Model to time applications at or above a 20–30% risk threshold.
• Rotate FRAC codes to reduce resistance risk and avoid back-to-back applications of single-site chemistries.
• Root Disease Management:
• Pythium Root Rot: Saturation and Soil Temperature-Driven
  Pythium root rot is triggered by prolonged soil saturation and moderate to warm temperatures. It is most common in compacted greens on poorly drained sites when soil temperatures exceed 55°F.
  Prevention Program:
• Begin applications when 2″ soil temps reach 55-60°F.
• Alternate the following on a 14-day interval:
• Segway^® Fungicide SC: 0.9 fl. oz./1,000 sq. ft.
• Serata™ Fungicide: 0.6 fl. oz./1,000 sq. ft.
• Tank mix with phosphites to enhance suppression and improve turf stress tolerance.
• Apply 1/8″–1/4″ irrigation immediately after treatment to move actives into the root zone.
• Summer Patch: Start Preventive Programs Early
  Summer patch, caused by Magnaporthe poae, thrives in compacted, moisture-stressed turf during warm weather. Symptoms typically emerge in midsummer, but effective suppression begins weeks earlier. Initiate preventive programs when soil temps reach 60–65°F.
• Tekken^® (3.0 fl. oz./1,000 sq. ft.) offers excellent summer patch suppression through dual-action DMI (tebuconazole) and SDHI (isofetamid) chemistry.
• Improve drainage and relieve compaction with aeration.
• Water-in all applications with 1/8″–1/4″ irrigation to ensure crown and root zone coverage.
• Fairy Ring & Waitea Patch: Manage Together in Spring
  Fairy ring symptoms include Type I (turf decline from hydrophobic soils), Type II (dark green rings), and Type III (mushroom-producing arcs). Waitea patch (Waitea circinata) can occur around the same time, especially on low-mown cool-season turf, and presents as circular yellow to orange patches with thinning turf. Fortunately, both diseases can be managed preventively using the same strategy.
  Recommendations:
• Begin preventive applications when soil temps reach 55°F.
• Apply Pedigree at 3.25 fl. oz./1,000 sq. ft. on a 28-day interval with a wetting agent.
• Apply in 2 gallons of water per 1,000 sq. ft. and irrigate immediately with 1/4″ to move the fungicide into the thatch and soil.
• Maintain regular aeration and thatch management.
• Pedigree provides proven control of both fairy ring and Waitea patch when timed properly in spring.

FORMULATION CHEMISTRY

• Pre-emergent applications will be applied during the March-May months depending upon the geographic location. Some of these products may be formulated as WP (wettable powders) with variable rates of application. High application rates to increase product longevity should be done without additional tank mix partners. This is especially true if a low volume spray “rig” will be used.
• If WP (wettable powders) are used for an application, please note that constant agitation is required to maintain tank mix homogeneity.
• Most pre-emergent chemistries are classified as “legacy” meaning they have been in the market for many years. These chemistries include prodiamine, dithiopyr, trifluralin and benefin, all of which have excellent chemical stability at various water pH, hardness and dissolved solids levels.
• Pre-emergent herbicide chemistries were originally developed as dyes. Plan on having a good tank mix cleaner to clean the tank and lines following application. This is also important to prevent product carryover to your next application.