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Agronomy Journal Abstract -

Four-Year Response of a Kentucky Bluegrass-Red Fescue Turf to Plant Growth Retardants1


This article in AJ

  1. Vol. 76 No. 5, p. 807-813
    Received: May 19, 1983

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  1. Peter H. Dernoeden2



Most research on plant growth retardants (PGR's) for turfgrasses has involved single and occasionally two annual PGR applications. The objectives of this study, however, were to evaluate longer term effects of PGR usage on turf density, quality, and canopy height by applying various rates of ethephon [(2-chloroethyl) phosphonic acid], flurprimidol {α-(l-methylethyl-α-[4-(trifluroro-methoxy) phenyl]-5-pyrimidinemethanol}, mefluidide {N-[2,4-dimethyl-5[[(trifluoro-methyl)-sulfonyl]amino]phenyl] acetamide}, and MBR 18337 (MBR) [N-(2ethylthio)-2-(trifluromethyl)phenyl methanesulfonamide] twice annually, for 4 consecutive years to a Kentucky bluegrass (Poa pratensis L.)-red fescue (Festuca rubra ssp. rubra L.) turf grown on a Chillum silt loam soil (fine-silty, mixed, mesic Typic Hapludult). The field data presented were combined over months and years for 1980, 1981, and 1982. Furthermore, 8 months following the final PGR application, turf plugs collected from field plots were evaluated for tiller and thatch production, leaf growth, and root recuperative potential. All PGR's reduced canopy height significantly from June to September. Mefluidide and MBR provided the most rapid growth suppression; however, flurprimidol provided a longer period of growth inhibition. Mefluidide and MBR caused leaf yellowing and necrosis shortly following application. Discoloration elicited by flurprimidol appeared several weeks following application in the form of leaf tip necrosis, but not death of entire leaves. Flurprimidol treated turf also developed an undesirable blue-green color during periods of heat and drought stress. Ethephon treated turf generally possessed a dark green color during summer. Between September and April, however, many ethephon treated plants developed necrotic sheaths. Ethephon caused elongation of internodes, and crowns of many plants were elevated several mm above the soil surface. Crown elevation gave the turf a ‘puffy’ quality and resulted in a large reduction of verdure when mowed. Mefluidide and MBR reduced turf density, which resulted in a severe infestation of crabgrass (Digitaria spp.). Crabgrass infestation was not a problem in flurprimidol and ethephon treated turf. Mefluidide and MBR effectively suppressed seedhead production; whereas, flurprimidol (2.2 and 3.4 kg a.i. ha−1) enhanced their production. Flurprimidol treated turf had more tillers and leaves than turf treated with other PGR's. Signficantly higher root weights were associated with flurprimidol G (2.2 and 3.4 kg ha−1) treated turf; however, root weight was positively correlated (r=0.80*, significant at the 0.05 level) with tiller number. Data revealed that two annual applications of the PGR's evaluated caused adverse effects that would limit their use on intensively managed turf. There were, however, no deleterious effects of PGR usage upon tiller and root recuperative potential of the Kentucky bluegrass-red fescue turf.

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