Summer Stress Management Summary

Published in the July 2015 Issue Published online: Jul 03, 2015 Dr. Gordon Kauffman III Agronomist and Technical Manager, BRANDT/Grigg Brothers

At Grigg Brothers, we strive to generate and compile data into a set of actionable and easily executed practical solutions for turfgrass managers.

Leading into the 2015 growing season, we are providing our sum­mer stress management, and spe­cifically our “anthracnose” manage­ment story based on 10+ years of research data. We’re excited to of­fer up advice for turf managers that builds on our existing and effective nutritional Integrated Pest Manage­ment (IPM) strategies designed to maximize plant health, limit nutri­tional losses to the environment, reduce chemical inputs and save turf mangers money.

Over the years we’ve published extensive information centered on maximizing turf health culturally and through correct chemical use. Our nutritional IPM programs offer effec­tive solutions that provide economic and environmental benefits.

Plant Health – New Technology as a Tool

This is an exciting era for plant nutrition as we gain a better under­standing of plant nutrition, develop more efficient nutrient formulations and consider the use of “elicitors” (see Elicitors and Turfgrass Man­agement: Correct Use and Discov­ery ) as a tool to further maximize plant health under environmental stress.

Turfgrass Stress Management – The Basics

Stress management programs are most effective as a supplement to existing and sound cultural prac­tices including mechanical cultiva­tion, sand topdressing, fertilization, irrigation management, and mow­ing practices. Stress management focuses on preventative mainte­nance by correctly using elicitors to achieve subtle—yet productive results when turfgrasses are sub­jected to biotic and/or abiotic stress (see PK-Plus offer Turf Manages an Important Nutritional Pest Man­agement Tool and Programs to Decrease Creep­ing Bentgrass Summer Stress and Lessen Anthracnose Severity on Poa annual Putting Greens ).

Grigg Brothers is considered by many as the leader in current elicitor research and effective integration into practical programs designed to manage turfgrass stress using PM. Our Proven Foliar fertilizer tech­nology provides chelated nutrient options which represent the most effective, efficient and safe nutrient source available to turf managers.

Phosphite Fate

An important and recent innova­tion includes the evaluation of phos­phite (H2PO3-) accumulation in plant tissue after treatment with PK-Plus (3-7-18 + 14% H2PO3-). This work demonstrated the systemic nature of H2PO3- once absorbed by leaf tissue and has led to the most ef­fective product application rate and timing recommendations. Phosphite accumulated in leaf tissue after the application of 0.35 g H2PO3- m-2 [6 fl. oz./1000 ft2 (M) PK-Plus] and reached its highest concentration (4,889 ppm) 48 hr after application (Figure1).

As expected, H2PO3- translo­cated to root tissue but was found in smaller concentrations—a range of 55-492 ppm. Based on field ob­servations, we estimate the need to maintain tissue H2PO3- concentra­tions ≥ 1,800 ppm (see dashed red

line Figure 1), therefore a two-week application interval of 6 fl. oz./M PK-Plus is recommended (Figure 1).

Not all phosphite fertilizers are created the same, and turf manag­ers should select products proven to get results. More than 10 years of research and field results verify that routine use of PK-Plus is an effec­tive stress and management tool that also provides mineral nutrition for better quality and more depend­able turf.

PK-Plus is the only foliar fertilizer scientifically documented as an ef­fective approach to managing the summer decline of cool and warm season grasses, including anthrac­nose (Collectotrichum cereale), mi­crodochium patch (Microdochium nivale), pythium (Pythium spp.), and root-knot nematodes.


Anthracnose Management

Our anthracnose ‘story’ is based on 10 years of research. Anthrac­nose (Colletotrichum cereale) has become a major disease problem on annual bluegrass (Poa annua) putting greens (Figure 2). An inte­grated approach remains essential to manage this disease effectively.

Initial research from 2003 indicated that the use of potassium phos­phite in the form of PK-Plus could lessen the severity of anthracnose compared to the fertilizer alone (Gary’s Green) and control treat­ments. Phosphite (H2PO3-) provides disease management options and plant health benefits that result from the upregulation of the turf’s natural defense mechanisms such as anti­oxidant production.



  • Supply adequate soluble nitrogen (N) – Low dose and frequent applications of N (0.1– 0.2 lbs/M) will reduce disease pressure.
  •  PK-Plus alone will provide some level of suppression but not acceptable.
  • A significant interaction between PK-Plus and contact fungicides occurs—compared to the sum of each individual part (PK-Plus or contact fungicide applied alone). Consistent research results document the synergy associated with repeat applications of 6 fl. oz./M of PK-Plus combined with 1.8 oz/M of Daconil Ultrex. This combination, even under severe disease pressure, provided excellent anthracnose suppression and equal to more elaborate fungicide programs.
  • The contact fungicide (Daconil Ultrex, Medallion, Chipco 26GT) rates were preventative and low label rates.
  • Better suppression was achieved when the rate of contact fungicide was increased under climatic conditions conducive to severe disease pressure. (eg. Daconil Ultrex 1.8 oz/M 3.2 oz./M)
  • Combining PK-Plus with Daconil Action (3 oz./M) provided the best suppression compared to Daconil Ultrex.

Importantly, the nutritional value associated with the Grigg Brothers Proven Foliar nutrient program(s) also provide excellent turfgrass color and overall quality. These results clearly demonstrate the effective use of a highly efficient foliar nitrogen (N) source and PK-Plus, applied in combination with 1.8 oz./M chlorothalonil under moderate pressure and 3.2 oz./M under heavy disease pressure for the best anthracnose management results.

Recently scientists from Rutgers University have identified critical soil test (50 ppm–Mehlich 3 extractant) levels and plant tissue levels (2%) for potassium (K), as it relates to anthracnose incidence and severity. They discovered an inverse correlation—as soil and tissue K increase the incidence of anthracnose decreases. This discovery provides valuable insight for further study.

Is this what makes PK-Plus (K2PO3-) such an effective tool for anthracnose management?

And do different phosphite salt formulations (Ca or N – PO3-) perform differently in this regard?

Grigg Brothers will address these questions and attempt to answer them during the 2015 growing season—so stay tuned.