Fertilizers containing phophonate compounds (those with a carbon to phosphorus bond), and specifically phosphate (HPO3-), have recently become a reliable management tool for turfgrass managers. Phosphite is an alkali metal salt of phosphorus acid, typically formulated as potassium phosphite (KH2PO3-), and has been documented to accumulate in plant tissues after application of fosetyl-Al, the active ingredient in the fungicides Alliete and Signature (1). Landschoot and Cook (2005) provide an excellent review of phosphonate products including important terminology and concepts.
Phosphate vs. Phosphite
Grigg Brothers® Proven Foliar™ fertilizers which contain phosphate are designed to provide nutritional value in the form of primary and secondary macro, and micro nutrients in addition to potassium phosphite. Phosphate (H2PO4-) is the plant available from of phosphorus and plays a key role in primary metabolic processes such as photosynthesis, energy production and transfer, and defense response pathways. Consequently, a Proven Foliar™ fertilizer formulated with plant available phosphate and phosphate is beneficial and practical. Phosphite provides little nutritional value (see picture above), but its documented benefits include:
- Promotes increase plant health and metabolic functioning
- Stimulates a plants natural defense mechanisms including phytoalexin and antioxidant production (3)
- Directly limits the growth and development of the oomycetes (Pythium spp., Phytoplora, and Plasmopara) classification of organisms in laboratory experimentation (4)
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Plant Defense Responses
Plants naturally defend against biotic and abiotic pests by triggering specific metabolic responses after pathogen infection, or the onset of adverse environmental conditions such as drought, heat, or salinity. Phosphite has been documented to upregulate these vital metabolic processes necessary for maximum plant health.
Benefits of Proven Foliar™ phosphate fertilizers containing phosphate are:
- Phosphorus nutrition is important for turfgrass abiotic stress tolerance and often unavailable (complexed) in the soil.
- Phosphite stimulates additional plant defense responses
- Phosphite can be used as one component to an integrated pest management program (see back)
- Optimum turfgrass health is maintained with adequate primary and secondary macro and micronutrient nutrition
- Application of phosphate under P deficiency conditions could be detrimental to plants
Phosphite and Pathogen Invasion
Phosphite appears to provide direct and indirect activity which lessens the severity and incidence of pathogen invasion, and should be used as one component of an integrated approach to disease management. In laboratory experimentation it has been shown that phosphites are most active when challenged with Phytopthera, but they did show activity against all Pythium species, including higher activity than fosetyl-Al treatments (4). Our field research confirms these findings (see reverse).
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Research
Research conducted by Grigg Brothers® has assessed the use of P-K Plus®, a Proven Foliar™ fertilizer containing phosphate and phosphate, as part of a summer stress syndrome program. In addition, trials were designed to determine its efficacy and use as part of disease management program, including turfgrass challenged with pythium blight (Pythium spp.), and anthracnose (Collectotrichum graminicola).
Results
P-K Plus®, when combined with traditional Proven Foliar™ fertilizers and applied on a 14 day interval, significantly improved overall turfgrass quality compared to the control, and provided similar quality to a fungicide program.
Perennial ryegrass treated with P-K Plus® had less Pythium than a fertilizer check and was similar to phosphonate fungicides and fosetyl-Al.
The addition of P-K Plus® to Gary’s Green® lessened the severity of anthracnose, and the combination provided better control than the untreated check.
Proven Foliar™ programs are designed for efficiency, performance, and compatibility. The programs also increase a turf managers control over nutrient availability and promote plant health.
Maximize Phosphite Applications by:
- Utilizing a product that contains plant available P in addition to phosphite in order to promote plant health.
- Applying sequesntially, pior to abiotic stress or before envirnmental conditions become conductive to disease development
- Apply in 1-2 Gallons of water per 1000 ft2
Proven Foliar™ Programs
Grigg Brothers® Proven Foliar™ programs are designed for efficiency and compatibility. The programs also increase a turf managers control over nutrient availability and promote plant health.
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Literature Cited
1. McDonald, A.E., B.R. Grant, and W.C. Plaxton. 2001. Phosphite (Phosphorus Acid): Its relevance in the environment and agriculture and influence on plant phosphate starvation response. J. Plant Nutr. 24 (10): 1505-1519.
2. Landschool, P. and J. Cook. 2005. Sorting out the phosphonate products. In Golf Course Management. November: 73-77
3. Guest, D.I. 1985. Fosetyl-Al: Control of plant diseases utilizing the plants own defense mechanisms. Acta Horticulture. 166: 63-64.
- Fenn, M.E., and M.D. Coffey. 1984. Studies on the in vitro and in vivo antifungal activity of Fosetyl-Al and phosphorus acid. Phytopathology. 74(5): 606-611.
DaconcileUltrex™ and Subdue™ are trademarks of Syngenta Crop Protection, Inc. Signature™ is a trademark of Chipco© and Backed by Bayer©. Aliette™ is a trademark of Bayer Crop Science©. Vital Sign™ is a trademark of Luxembourge Industries Ltd.
