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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.