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Physiological Effects of Phosphite Formulations on Turfgrass Challenged with Pythium and Heat Stress. Year II (2006) |
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Objectives:
Determine whether formulation is important in terms of phosphite source and additives for control of Pythium blight.
Determine impact of phosphite based products on turf quality and color.
Confirm whether phosphite based products reduce algae cover on greens.
Field Locations: Sand-based Penn A4 creeping bentgrass green at TRC, Blacksburg
USGA Penn A1 & Penn A4 creeping bentgrass green at Bayville C.C., Virginia Beach
Perennial ryegrass fairway at Waterfront C.C., Moneta Treatment List (product rate in ounces/1000ft2): 1. Untreated 6. Vital Sign (6)
2. PK Plus (6) + GGU* (9) 7. Subdue Maxx (1)
3. Fairphyte (4) + GGU (9) 8. Signature (4)
4. Fairphyte (6) + GGU (9) 9. Aliette (4)
5. Nutrol (6 lbs/100 gal) + Prudent 44 (2) 10. EleMax (5)
*GGU = Gary's Green Ultra
Procedures:
Trials were conducted at three different locations across Virginia. Applications of each treatment were made every 14 days at each site, beginning May 16 in Virginia Beach, June 1 in Blacksburg, and June 30 in Moneta. Each treatment was replicated four times and arranged in a randomized complete block design. Foliar applications were made with a carbon dioxide pressurized sprayer equipped with a TeeJet XR11004VS spray tip. The dilution rate was 2 gallons of water per 1,000 square feet. Plots that did not contain Gary’s Green Ultra (GGU) were normalized with equivalent amounts of nitrogen in the form of 20-20-20 soluble fertilizer.
In Blacksburg and Virginia Beach, multiple attempts were made to induce disease development by inoculation with Pythium and tarp covering. Disease began to develop in Virginia Beach but not in Blacksburg. Development of Pythium blight in Moneta occurred Plots were visually rated periodically using a 1-9 scale for turf quality (1 = dead turf, 5 = acceptable, 9 = superior) and color (1 = highly chlorotic, 5 = acceptable green, 9 = deep green). Percent disease or percent algae cover were estimated when applicable. A Field Scout TCM 500 (NDVI model) was also used to measure turf color and converted to a Grass Index number (1-9 color scale). Data were subjected to analysis of variance and compared by means of Least Significant Difference (LSD) test. The level of significance (alpha) for the comparisons is 0.05.
Results:
No phosphite product consistently provided a significant increase in turf quality or color at either creeping bentgrass location. Of the dates where color was rated in Blacksburg, Signature plots and treatments that contained Gary’s Green Ultra had significantly better color than untreated plots on three and four dates, respectively. Grass Index ratings confirmed that there were little or no significant differences.
Results from the perennial ryegrass fairway confirmed last year’s data showing that phosphite fertilizers provided significant control of Pythium. In Virginia Beach, Pythium blight was rated two times after inoculation. There was variable control of Pythium with different products, and on one rating date, Prudent 44 plus Nutrol had significantly more disease than untreated plots.
Suppression of algae was significant at the Blacksburg site for a second consecutive year with both phosphite fertilizers and fungicides, though the results were not as dramatic this year as they were last year.
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release 1/19/2011 |
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