PLANT GROWTH REGULATORS

By John Kmitta

In 2020 , the industry dealt with shutdowns , labor shortages and other challenges , many sports field managers turned to plant growth regulators ( PGRs ) to help bridge the gap during periods of reduced mowing and maintenance . But as sports are in full swing throughout the country , and many fields are exposed to increased traffic , how do PGRs fit into a sports field management program ?

“ I believe there are three main fits for PGRs in a sports field management program ,” said Rick Fletcher , technical services manager , Turf and Ornamentals , at Nufarm . “ Mowing management , playing surface consistency , and overall appearance [ turf color ]. Additional considerations , depending upon the site and grass species , could be poa annua management and in-field markings or painting applications .”

Said Aaron Hathaway , Ph . D ., technical services manager , Turf and Ornamentals , at Nufarm , “ Especially in cool-season turfgrasses , we can see a rebound in turf growth when growth regulation is lifted or wears off in the plants . We actually see more growth in the plant than if we had never applied a PGR unless another application is applied . This means we can manipulate more growth in the turf plants when we stop applying PGRs altogether .”

As a result , sports field managers have begun to apply PGRs during the growing season to maximize turf health by limiting vertical growth and the spending of energy on this mowed vertical growth . Then , before heavy practices begin , they will cease use of PGRs and gain the benefits or the rebound effect where more growth occurs and divots and wear can be more quickly recuperated , Hathaway added .

OVERALL BENEFITS According to Fletcher , the use of latestage gibberellic acid ( GA ) -inhibiting products on cool-season turf species provides several benefits , such as increased tiller density , increased rooting potential and color enhancement along with reduced shoot growth leading to mowing management reductions .

“ These changes in plant growth have been shown to directly improve playing surface stability [ divots and slips ] and consistency [ ball roll / bounce ],” said Fletcher .

According to Dean Mosdell , Ph . D ., technical services manager for Syngenta , there are several benefits to plant growth regulators :

Reduced clippings : PGRs can help reduce the amount of grass clippings , resulting in less green waste , reduced mowing time and labor savings .

Maintenance of painted lines and logos .

Better turf quality : PGRs can increase turf density and root growth for better wear tolerance and recovery .

Pre-stress conditioning : PGR applications made prior to heavy-use periods or special events can help enhance recovery .

Water use efficacy : Multiple applications can reduce water use , resulting in tolerance of low light levels , heat stress and other abnormal weather patterns .

PROPER APPLICATION AND OTHER CONSIDERATIONS “ Remember that the ‘ G ’ in PGR stands for ‘ growth ,’ so avoid situations where the turf is stressed [ heat , water ], damaged [ disease , insects , excessive play ], and when planned cultural practices are to take place [ aeration , verticutting ],” said Fletcher . “ Turfgrasses under regulation will be much slower to recover from any or all of theses events .”

Mosdell added that plant growth regulators should be applied when the turf is actively growing . Repeat applications based on growth rate ( amount of clippings produced ) or a growing degree day model . Apply in at least 44 gallons water per acre for adequate coverage with a foliar-absorbed product and leave on the foliage for at least one hour .

According to Fletcher , it is also important to understand how your chosen PGR product absorbs into the target plant , foliar or root ; how fast typical absorption takes place ; and the effects of water quality and application calibration on deposition and absorption .

“ For example , late-stage GAinhibiting products are predominantly foliar absorbed within the first one to four hours after application / deposition ,” he said . “ If this type of PGR product was used in a tank mix that was immediately watered in , the products would be moved away from the leaves and the desired effects greatly diminished .”

Hathaway added that a foliarabsorbed PGR makes sense in athletic field situations where there is often constant overseeding with perennial ryegrass to make sure seed is available to germinate and fill in thinned , stressed and / or divot areas . These foliarly absorbed PGRs , if applied before seed germination , won ’ t be absorbed by young germinated seeds . SFM

John Kmitta is associate publisher and editorial brand director of SportsField Management magazine . sportsfieldmanagementonline . com June 2021 | SportsField Management

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