PGRs and TGRs

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PGRs and TGRs
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Different Modes of Action- Type I and Type II

• Type I growth regulators inhibit cell division.
• Type I growth regulators are foliar absorbed.

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Different Modes of Action- Type I and Type II

• Most Type I Growth regulators are older materials
  that cause some phytotoxicity on grass.
• Mefluidide (Embark) is utilized more than any
  other type I growth regulator, but it yellows and
  thins turf when used during hot weather
  conditions.

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Different Modes of Action- Type I and Type II

• Maleic hydrazide (MH-30, Royal Slo-Gro) is one of
  the oldest growth regulators used on turf, and
  causes extensive yellowing.

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Type I- Growth Regulators

• Embark (mefluidide) is also used to inhibit seed
  head formation of Poa annua to improve the
  appearance and playability of fairways.
• The rate used for seed head suppression is
  1/12-1/16 of the growth regulation rate.

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Type I- Growth Regulators

• Timing is critical- must be within two weeks of
  flowering to be effective.
• Usually about two weeks after the first mowing is
  a good time to apply.
• Some yellowing may still occur, but this can be
  reduced by using products like Ferremec.2
• If you are going to try it, read the label
  thoroughly!

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Type II Growth Regulators

• Type II growth regulators work by inhibiting
  biosynthesis of gibberellin.
• Since, gibberellin causes cell elongation, little
  or no elongation of cells occurs when GA is
  inhibited.

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Type II Growth Regulators

• Type II growth regulators include
• Cutless (Flurprimidol),
• Limit (amidochlor),
• Primo (trinexapac- ethyl)
• TGR Turf Enhancer (paclobutrazol)
• http//www.uhsonline.com/prodframe.php

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Type II Growth Regulators

• Type II growth regulators generally are less
  phytotoxic, and some actually have benefits other
  than reduced growth.
• Amidochlor (Limit) is less damaging to turf than
  type I growth regulators, but still should not be
  used on high maintenance turf.

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Type II Growth Regulators

• Many superintendents have tried Type II growth
  regulators as a means of reducing Poa annua on
  their golf courses.
• http//www.andersonsgolfproducts.com/st_poaannua.a
  sp

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Type II Growth Regulators

• Growth in Poa annua is reduced more than in
  Agrostis palustris, giving the creeping bentgrass
  a chance to spread into the territory held by Poa
  annua . (1,2,3,4,5)
• Cutless, TGR Turf Enhancer and Primo have all
  been used in this way with varying degrees of
  success. (1,2,3,4)
• Cutless and TGR Turf Enhancer are most effective
  in suppressing Poa annua but they also cause
  yellowing which may be unacceptable.

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Type II Growth Regulators

• Other possible benefits of type II Growth
  Regulators include
• Reduced mowing- the duration of suppressed growth
  varies considerably (usually 4-7 weeks) depending
  on species, environmental and growth factors.
  (1,2,3,4)

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Type II Growth Regulators

• Increased shoot density- more tillering (1,2,3,4)
• Reduced water use- lower ET rates have been
  observed with Primo, Cutless and TGR.
• However, Primo was the only material that
  enhanced turf quality during dry down in one
  study. (4)
• Longer disease suppression with contact
  fungicides ??

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Type II Growth Regulators

• Flurprimidol and paclobutrazol have been shown to
  reduce dollar spot disease incidence somewhat on
  creeping bentgrass.
• Improved green speed at mowing heights gt 1/8
  (research doesnt back this theory up)

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Cutless
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Type II Growth Regulators

• There are also some possible negative effects of
  Type I and II Growth Regulators. They include
• Reduced uniformity- regulation of growth can vary
  between grasses resulting in non- uniform
  appearance.

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Type II Growth Regulators

• rebound effect- after the growth regulator
  wears off, there is often a flush of growth
  resulting in reduced turf quality and a need for
  increased mowing.
• Primo and Embark have caused this response.
• Increased weed problems- some weeds,like
  goosegrass, have less of a reduction in growth
  rate than turfgrasses.
• Moreover, some weed species like crabgrass
  increase in shoot production due to increased
  tillering caused by some PGRs. (5)

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Type II Growth Regulators

• Slower recuperation from injury?
• Increased susceptibility to some diseases? Type
  I growth regulators have shown to cause increased
  disease problems.(2)

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New Classification Scheme for TGRs

• A new way to classify growth regulators has been
  developed using classes A,B,C, and D.
• Class A materials are GA inhibitors that
  interfere with GA synthesis late in the
  biosynthetic pathway.
• Only Trinexapac-ethyl is in the category.

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New Classification Scheme for TGRs

• Class B materials interfere with GA synthesis
  early in the biosynthetic pathway.
• Fluprimidol and paclobutrozol are included in
  this class.
• Class C materials inhibit mitosis.
• Hyradazide, mefluidide and amidochlor are in
  this category.
• Class D materials are phytotoxic (can kill
  plants) but have a growth regulating effect at
  very low rates.
• Glyphosate (Roundup) and chlorsulfuron (Telar)
  are examples.

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A New Growth Regulator for Turf

• Proxy (ethephon) recently received a label for
  turfgrass use.
• Ethephon works by releasing ethylene into
  turfgrass leaves. (2)
• Ethephon has a more subtle action than type I or
  type II inhibitors with no noticeable change in
  growth habit for about 2 weeks.(2)

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A New Growth Regulator for Turf

• Ethephon does not fit into the A,B,C,D scheme of
  classification either.
• Ethephon has no rebound effect like Primo and
  Embark do.

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A New Growth Regulator for Turf

• Proxy may be very effective in battling Poa annua
  with growth reduction as high as 90 with an
  average of 38 over seven weeks
• Bentgrass growth reduction with Proxy was a
  maximum of 50 and a 14 average over seven
  weeks. (2)

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A New Growth Regulator for Turf

• Proxy is not labeled for greens- further testing
  needs to be done.
• Proxy is also labeled for Poa annua seed head
  supression.
• Nick Christians claims that Poa pratensis treated
  with Proxy changed in form to an almost
  stoloniferous growth habit, which might improve
  wear tolerance.

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Fertility and Growth Regulators

• It is generally best to keep fertility levels
  somewhat higher on turf treated with growth
  regulators than on non- treated turf because
• Growth regulation effects seem to be enhanced at
  higher fertility levels.
• Higher fertility levels help to mask the
  chlorosis that sometimes appears when growth
  regulators are used.

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Seedhead Management Plant Growth Regulators

• Poa is not a single, uniform turf species.
• It has a large number of turf subspecies or
  biotypes.

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Seedhead Management Plant Growth Regulators

• Poa annua can range from
• annual types that die each spring following a
  period of intense seedhead formation.
• Biotypes that live for several years and flower
  later in the season for longer periods of time.
• It is impossible to predict which biotypes you
  have on your course.
• The many biotypes is the 1 reason its so hard to
  predict precisely when the seed will form.

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Seedhead Management

• At courses where Poa is tolerated, reducing seed
  heads makes a difference.
• Most seed head management has relied on a
  combination of cultural practices and
  applications of PGRs.
• The cultural practices used to improve mowing
  when seed heads are present include brushing and
  vertical mowing.
• Proxy is becoming the preferred chemical for seed
  head management.

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Seedhead Management PGRs

• Mefluidide is well known for its ability to slow
  down or stop seedhead formation.
• Mefluidide is used to inhibit Poa Seedhead
  formation on golf courses.
• Under optimal conditions, applications can result
  in 85 90 Poa annua seedhead suppression.
• There are some drawbacks of using this product.

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Drawbacks of Using Mefluidide

• Varying Turf Response
• -Using PGRs to slow seedhead formation came
  into use in the 90s, but results vary greatly
  by location.
• -Seedhead suppression will last from 3 6
  weeks.
• -To keep seedheads formation consistently low,
  you will need to increase the rate gradually
  after each application.
• -Success depends greatly on the skill of the
  superintendent to adapt the program to his or her
  course.

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Drawbacks of Using Mefluidide

• Timing of the First Application
• -Because this product does not affect seedheads
  that already exist the first application needs to
  be made two weeks before the first flush of
  seedheads.
• -The first application will need to be at
  different times in different location or
  different climates.

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References

• 1. Christians, Nick, Creative Uses for Turfgrass
  Growth Regulators, USGA Green Section Record,
  September-October 2001, p.11-13.
• 2. Dernoeden, Peter. Creeping Bentgrass
  Management. Sleeping Bear Press, Inc. Chelsea,
  MI, 2000.
• 3. Diesburg, Kenneth. A New Growth Regulator for
  Golf Course Turfgrass. Golf Course Management.
  November 1998.
• 4. Fermanian, Tom. Managing Bentgrass Fairway
  Growth with PGRs. Grounds Maintenance. May 1997.

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References

• 5. Fry, J.D. Plant Growth Regulators May Help
  Reduce Water Use. Golf Course Management.
  November 1998.
• 6. Lowe, Todd et al. Some weeds Flourish Under
  Growth Regulators. Golf Course Management.
  September 1999.

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LINKS

• http//www.grounds-mag.com/managing.htm
• http//virtual.clemson.edu/groups/hort/sctop/TURFS
  ec/weedsci/weedsci5.htm
• http//www.cp.us.novartis.com/products/specialty/P
  rimoWSB.shtml
• http//link.springer-ny.com/link/service/journals/
  10088/bibs/38n4p1028.html
• http//www.turf.uiuc.edu/itf/tips/tt97-2.html

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LINKS

• http//www.hort.iastate.edu/pages/news/turfrpt/199
  9/greenpoa98.html
• http//www.msu.edu/user/rogersj/laplata.html
• http//edis.ifas.ufl.edu/scripts/htmlgen.exe?DOCUM
  ENT_WG064