1. 4/26/2012
Plant Growth Regulators (PGR’S)
Why:
• Reduce growth
• Reduction in labor costs
• reduced mowing
• reduced clippings
• Reduce growth when overseeding
• Chemical edging around trees etc
• Hillsides
• Some PGR’s suppress poa seed
head
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2. 4/26/2012
Why PGR’s Continued:
• Improve the health of the plant
• Density
• Drought stress-less water use
• Color
• Root development
• Increase putting green speed
• Increases in shade tolerance
• Increase wear tolerance
What are PGR’s?
Original classification
Type I and Type II growth regulators:
Type I
• Compounds foliar absorbed and inhibit
cell division at the meristem
• Excellent seedhead control
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3. 4/26/2012
What are PGR’s continued?
Type II
• Crown or root absorbed
• Inhibit or suppress both growth and
development
• Suppression due to inhibition of
gibberallic acid
• Usually less phytotoxic
• No effect on seedhead formation just
elongation of seed stalk
New Classification PGR’s
- All reduce growth -
Class A:
• Late gibberellic acid (GA) synthesis blockers
(giberellic acids hormones responsible for
cell elongation)
• Example Primo Max® (trinexapec-ethyl)
• Foliar absorbed
• Last 3-6 weeks depending on rate and use
Class A continued:
USE
- poa reduction
- Color enhancement
- Overseeding reduction in
competitiveness of existing species.
• germination and development of new
seed is normal because of:
* late gibberellin synthesis inhibition
* class A are foliar absorbed
- Increases in shade tolerance
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4. 4/26/2012
Class B:
• Early GA synthesis blocker
• Trimmit® (paclobutrazol), Cutless®
(flurprimidol)
• Root absorbed
• Use- poa reduction
Class C:
• Mitotic inhibitors
• Slo Gro® (maleic hydrazide), Embark®
(mefluidide), Limit® (amidochlor)
• Foliar or root absorbed
• Use- poa seedhead suppression
• May need to add fungicide, nitrogen,
or iron
Class D:
• Herbicidal mode
• Oust® (sulometuron-methyl), Round-up®
(glyphosate), Telar® (chlorosulfuron),
Prograss® (ethofumestate)
• Foliar and/or root
• Phytotoxic growth regulating response at
low rates/herbicide at high rates
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5. 4/26/2012
Class E:
• Ethylene production enhancement
• Proxy® (ethephon)
• Foliar
• Use- poa seed head suppression
Turfgrass Establishment
Applications Class A products are often used
due to:
• Reduction in competitiveness of existing
species when overseeding.
• Seeding germination and development is
normal because of:
Late gibberellin synthesis inhibition of
class A are foliar absorbed
Management of Poa annua
Class C products often used:
•Direct suppression of seedhead
formation
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6. 4/26/2012
Chicago Golf Club (Kane 2001) Mixed Bentgrass
& Poa- 0.5” H.O.C. 18th Fairway
Proxy = Class E, Primo = Class A, Embark = Class C
Foliar - Seed Head --- Foliar----- --- Foliar or Root ---
Pebble Beach Golf Links, #14 Fairway
Pebble Beach CA (Mahady, 2001 )
Seed Heads Seed Heads
Color Quality % Cover % Control
5/15/2001 5/15/2001 5/15/2001 5/15/2001
Treatments 42 DAT 42 DAT 42 DAT 42 DAT
Untreated Check 6.8 d 8.0 b 34.8 b 0%
Proxy(5) 8.0 bc 9.6 a 1.4 c 96%
Proxy(5)+Primo(O.25) 8.4 ab 9.8 a 0.6 c 98%
Primo(O.25) 7.6 c 8.4 b 44.8 a 0%
Typical green spray = 5oz / 1,000sq.’of Proxy
plus
.125 oz / 1000 square feet of Primo
What can affect PGR’s
• Turfgrass species or cultivars
• Weather conditions
• Soil moisture
• Root absorbed PGR’s may require
irrigation
• Application timing
• Plant health
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