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What to expect from plant growth regulators Micah Woods November 20, 2018 Chief Scientist Asian Turfgrass Center www.asianturfgrass.com

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What has the potential to occur? from “Insecticides, fungicides, herbicides, and growth regulators used in turfgrass systems,” Reicher et al., 2013 • improve heat stress tolerance • improve performance in shade • increase green speed • decrease sod heating • improve density and color • increase drought and heat tolerance • delay fall dormancy of warm-season grasses • hasten spring green-up

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What has the potential to occur? • improve heat stress tolerance • improve performance in shade • increase green speed • decrease sod heating • improve density and color • increase drought and heat tolerance • delay fall dormancy of warm-season grasses • hasten spring green-up • reduced mowing requirement • reduced nutrient requirement • reduced water requirement

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from Reicher et al., 2013

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Today’s outline 1. Healthier plants 2. Better playing conditions 3. Lower resource use 4. Optimal application scheduling

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1. Healthier plants

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Manila Golf Club

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Manila Golf Club, February 2013

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Manila Golf Club, February 2013

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• slower growing • improved stress tolerance • improved shade tolerance • more efficient photosynthesis

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Table 1 from Grime, 1977

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2. Better playing conditions

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More plant density manilagrass at Keya GC, Japan

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Tolerance to lower mowing manilagrass at Keya GC, Japan

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Improved performance in shade manilagrass at Keya GC, Japan

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Possible root enhancement manilagrass at Keya GC, Japan

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3. Lower resource use

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The growth rate is slower, so there can be … less mowing Peak clipping yield suppression at label rates is about 50% of untreated. Mowing frequency reduction may be possible.

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The growth rate is slower, so there can be … lower CO 2 emissions Mowing fairways on an average 18 holes produces about 92 kg of CO 2 . With 150 fairway mows a year, that’s almost 14 tons of CO 2 .

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The growth rate is slower, so there can be … lower irrigation water use

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“by using a surfactant, a PGR, or both, bermudagrass quality can be maintained with 15 to 30% less irrigation water …without a reduction in color or quality.” Serena et al., 2018

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4. Optimal application scheduling

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How much growth reduction? “Peak suppression values after a [trinexapac-ethyl] application at 0.034 kg a.i. ha-1 [280 mL/ha] in this study ranged from 49 to 62%” Reasor et al., 2018

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When does the growth reduction happen? “Peak suppression occurred between 166 and 177 GDD calculated using 10°C as the base temperature (GDD10C )” Reasor et al., 2018

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Figure 1 in Reasor et al., 2018

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from Figure 1 in Reasor et al., 2018

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Recommended reapplication interval Based on the suppression of ultradwarf bermudagrass, Reasor et al. suggest a reapplication interval of 216 to 230 accumulated GDD10C . In days, with Manila weather, that works out to reapplication every 12 days on average to maintain consistent growth regulation.

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https://greenkeeperapp.com

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https://greenkeeperapp.com

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Minimal use recommendation • 3 applications prior to tournament • first app 33 days before tournament • second app 21 days before tournament • final app 9 days before tournament

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For more, please see www.asianturfgrass.com.