Turfgrass growth and seed head suppression by means of new plant

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					Chapter      Turfgrass growth and seed head
             suppression by means of a new plant
             growth retardant                 (1)


      68     P.C. BHOWMIK




                                           ABSTRACT
     Mon 4621 (flowable) and Mon 4622 (granular) [Acetamide, N-[(Acetylamino)
methyl]-2-chloro-N-(2,6-diethylphenyl)]  were evaluated to determine their
effects on seed head suppression and growth retardation of Kentucky bluegrass
(poa pratensis L.)-red fescue (Festuca rubra L.) turf. Both Mon 4621 and Mon
4~ when applied on May 3 (10~-UP-SUt           no mowing) or on May 12 (100%
green-up plus 2 mowings) provided better seedhead suppression than the May 21
application (100% green-up plus 18-day growth). Phytotoxicity to the
turfgrass due to these treatments was minimal. Turf quality was good to
excellent. Regardless of the time of application, the growth suppressing
effects were observed during the initial 42-day period and the reductions
ranged from 50% to 80%. The initial application of Mon 4621 at 2.2 kg ha-1
followed by a sequential application of Mon 4622 at 2.2 kg ha-1 35 days later,
reduced the top growth up to 70 days.
Additional   key words:   Phytotoxicity,     Poa pratensis,   Festuca rubra


                                      INTRODUCTI ON
      Research on growth retardants for use in turfgrasses has significantly
increased in recent years (Bhowmik, 1984a,b; Freeborg and Daniel, 1981;
Watschke, 1981). Growth retardants have been known to suppress seedheads
(Bhowmik, 1984b; Jagschitz, 1982; Sandbrink et al, 1983; Watschke, 1981) and
to reduce vertical growth (Dernoeden, 1984; Hurto, 1981; Welterlen and Nash,
1984). Growth retardants have also been documented to reduce mowing costs
(Bhowmik, 1984c; Jagschitz, 1982). Growth retardants have proved to be useful
in low maintenance turf9rass areas (Watschke, 1976). Injury to the turfgrass
(Bhowmik, 1984b; Schmidt and Bingham, 1977; Watschke, 1976), lack of unifor-
mity in response among species (Christians and Nau, 1984; Parups and Cordukes,
1977) are some of the factors that have limited their use in other turfgrass
areas including high maintenance turfgrass. Because of this, the research for
new and better growth retardants continues. The objective of this study was
to evaluate the effectiveness of Mon 4621 (4F) and Mon 4622 (2.5G) as a growth
regulator on cool-season turfgrass. Rates of application, timing of applica-
tion, and sequential application Mon 4621 and Mon 4622 were examined under
field conditions.


(1) A contribution  from the Department of          Plant and Soil Sciences,   Univerai ty
    of Massachusetts,   Amherst, MA01003.            Mass. Agric. Expt. Sta.   J. Article
   N°2692.
736                               P.C. Bhowmlk




                              MATERIALS AND METHODS


General
      Three experiments were conducted on a well established stand of 'Baron'
Kentucky bluegrass 'Penlawn' red fescue turf and the fourth experiment was
conducted on a monostand of 'Merion" Kentucky bluegrass at the Turfgrass
Research Center, South Deerfield, University of Massachusetts.   The soil was a
Winooski silt loam (Aquic Udifluvent) with a pH 6.4. The area was fertilized
twice annually with N at 24.39 kg ha-1• Mowing height was maintained at
3.8 cm. cutting height.
       Plots were 1 by 3 m in size and the treatments were replicated four times
in a   randomized complete block design. Granual formulations were applied by
hand   with a shaker bottle. All sprayable materials were applied with a back-
pack   C02 sprayer in 450 Lha-1 at 152 KPa. All treatments were applied to the
turf   that were 100% green-up unless otherwise stated.

Timing of Application
                                                                I

      Three separate experiments were investigated in 1982. In one experiment,
treatments (Table 1) were applied on May 3, when the turfgrass reached 100%
green-up but no mowing. In the second experiment, the same treatments were
applied on May 12, 1982 to the turfgrass that received two mowings following
100% green-up. In the third experiment, the same treatments were also applied
on May 21, 1982 when the turfgrass had 18 days of growth following 100% green-
up.

Sequential   Application

      Sequential applications of Mon 4621 (amidochlor) were made on Kentucky
bluegrass that was 100% green. Initial application was made on May 3, 1982,
followed by either May 28 or June 10 applications (Table 2).

      Five vertical height measurments per plot were made and the average
height was subjected to analysis of variance. Phytotoxicity was rated on a
scale of 0 to 100, 0 indicating no turf injury and 100 indicating complete
dead turf. A visual estimate of seedhead suppression on a scale of 0 to 100
was made in 1982. These were expressed as the percent reduction of seedhead
compared to that of untreated check plot. Turf quality was rated on a scale
of 1 to 9, where 1 means brown turf, 6 means commercially acceptable turf
(light green color), and 9 means dark green color turf. All these parameters
were determined 14, 28, 42, 56, and 70 days after treatment (OAT) from time of
application.    Data were subjected to analysis of variance and the treatment
means were separated by LSD at 0.05 level of probability.
                                                          Seedhead suppression                                                                              737




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738                                                                   P.C. Bhowmlk




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                             Seed head suppression                        739



                           RESULTS AND DISCUSSION

Timing of Application
     Phytotoxicity was determined three times 14, 42, and 70 OAT for May 3,
May 12, and May 21 application dates (Table 1). Mon 4621 (F) and MON 4622 (G)
at 2.2 to 3.3 kg ha-1 exhibited very little phytotoxicity to the turf,
regardless of the timing of application. However, some injury to the turf was
observed 70 OAT. Mefluidide [N-[2,4-dimethyl-5-[[(trifluromethyl)sulfonyl]
amino]phenyl]acetamide] generally caused the most injury to the turf. Similar
observations were made by Welterlen and Nash (1984). Bhowmik (1984b) reported
40 to 50% injury (June 28, 1983) to Kentucky bluegrass-red fescue turf with
the treatments of Mon 4621 and Mon 4622. In general, injury to the turf was
much higher in 1983 than in 1982.
     Mon 4621 (F) provided 58% to 75% seedhead suppression of Kentucky
bluegrass and 75% to 83% seedhead reduction for red fescue (Table 1).
Vertical height measurements were made at two-week intervals. All treatments
affected vertical height of turf grass (data not presented). Vertical height
of turfgrass descreased with time from the start of each application. Maximum
height reduction was noted with the May 3 application. Vertical height in
general increased 42 OAT, irrespective of the time of application.
     Turf quality was good to excellent with most of the treatments (Figure
1). Turf quality with Mon 4621 or Mon 4622 treatments varied greatly with the
timing of application. Maximum quality reduction was noted from the May 21
application. Mefluidide at 0.43 kg ha-l resulted in maximum reduction in turf
quality.
     Figure 2 illustrates the effects of various treatments on clipping weight
of the treated turfgrass. With May 3 application, mefluidide exhibited maxi-
mum reduction in clipping weight followed by Mon 4621 and Mon 4622. Man 4621
or Mon 4622 suppressed turfgrass growth for a longer period of time as com-
pared to mefluidide. Similar trends in clipping weight reduction were
observed with May 12 and May 21 application. However, with the May 21
application, the initial reduction in clipping weight 14 OAT was greater than
those obtained with either May 3 or May 12 applications. Regardless of the
timing of application, maximum growth suppression of the treated turfgrass was
observed 28 OAT. Mon 4621 and Mon 4622 provided extended period of growth
suppression, as evidenced by clipping weights, beyond 42 OAT •.
     Stimulatory effects of mufluidide on the turf was noted at an earlier
date (28 OAT plus 14 OAT) than that was noted with Mon 4621 or Mon 4622. The
stimulatory response was much greater with mefluidide than the response exhi-
bited by Mon 4621 or Mon 4622. Stimulation of turfgrass growth following
inhibition due to growth retardants has been reported by other researchers
(Bhowmik, 1984b; Hurto, 1981; Watschke, 1981).

Sequential Application
      Phtotoxicity to the turf was minimal 42 days after treatment (Table 2).
At 56 OAT, sequential applications of Mon 4621 showed increased phototoxicity
(up to 38%). Turf quality due to any of these sequential treatments was
excellent up to 42 OAT (Table 2). At 70 OAT, a slight reduction in turf
quality was noted with the treatments of sequential applications (May 28) than
those were applied on June 10 following initial application.
 740                                    P.C. Bhowmik




                  Mon 4 0 2 1   4F                     MAY 3   APPLICATION




                                                         MAY 2 t   APPLICATION




                                                    j|_y|



                    ABCDEFG          ABCDEFO       ABCDEFG           A8COEFQ



                                     DAY« AFTER   TREATMENT




Figure 1. Effects of various rates of Mon 4621, Mon 4622, and mefluidide on
          the quality of turfgrass 28, 42, 56, and 70 days after treatment.
          The 0 line represents the control. Bars extending below and above
          0 line represent decreases or increases relative to the untreated
          mowed check.
                               Seed head suppression                        741




                                ....   COEf   G




Figure 2.   Effects of various rates of Mon 4621, Man 4622, and mefluidide on
            the clipping weight of turfgrass 28, 42, 56, and 70 days after
            treatment. The 0 line represents the control. Bars extending
            below and above 0 line represent decreases or increases relative to
            the untreated mowed check.
742                                                                   P.C. Bhowmik




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                               Seedhead suppression                            743



     Vertical height reduction was noted with all treatments as compared to
the untreated turf (Table 3). Sequential treatments did not show any added
advantage in height reduction. Maximum seedhead suppression was noted with
the treatment of Mon 4621 at 2.8 kg ha-1,followed by 2.2 kg ha-1 application
on May 28. In general, seuqential treatments resulted in greater seedhead
reduction.
     Mon   4621 at 2.2 to 3.3 kg ha-1 resulted in substantial reduction of
clipping   weight (Table 4). Greater reductions in clipping weight were noted
with all   sequential treatments. The effects of growth retardation, as indi-
cated by   clipping weight, lasted up to 56 DAT followed by growth stimulation.
      In summary, growth suppression with either Mon 4621 or Mon 4622 was as
effective as with mefluidide application. Mon 4621 or Mon 4622 was effective
at 2.8 kg ha-1 with no adverse effects on turf quality. In general, phyto-
toxicity was less as compared to that with mef1uidide. Application of either
Mon 4621 or Mon 4622 on May 12 proved to be more effecitve in overall growth
suppression than either M~y 3 or May 21 application. A sequential appliation
of Mon 4621 at 2.2 kg ha-1 35 days later reduced the growth of turfgrass for a
10-week period without any objectionable injury.


                                 ACKNOWLEDGEMENTS
     The author wishes to express appreciation to Monsanto Chemical Co. for
the grant-in-aid support of these studies. Skillful technical assistance of
Edwin N. McG1ew is gratefully acknowledged. The author thanks Debbie Clark
for typing the manuscript.


                                LITERATURE CITED

 Bhowmik, P.C. 1984a. New growth retardants for cool-season turfgrass.
 1984 Meeting of the Weed Sci. Soc. of America. February, 1984. Abst.
 No. 88. pp. 33-34.
 Bhowmik, P.C. 1984b. Effects of growth retardants on turfgrass.       Proc.
 Northeast. Weed Sci. Soc. 38:315-320.
 Bhowmik, P.C. 1984c. Growth retardants: A possible management tool for
 use in reducing mowing costs. University of Massachusetts Turfgrass
 Field Day Report. 10:8-9.
 Christians, N.E. and Nau, J. 1984. Growth retardant effects on three
 turfgrass species. J. Amer. Hort. Sci. 109:45-47.
 Dernoeden, P.H. 1984. Four-year response of a Kentucky bluegrass - Red
 fescue turf to plant growth retardants. Agron. J. 76:807-813.
 Freeborg, R.P. and Daniel, W.H. 1981. Growth regulation of Poa
 pratensis l. p. 477-486. In R.W. Sheard(ed) Proc. 4th Int. iUrfgrass
 Res. Conf., Guelph, Ontario Canada. July 11, 1980. The Ontario Agril.
 College, Univ. of Guelph, Ontario, Canada.
 Hurto, K.A. 1981. Effects of EL500 on a Kentucky bluegrass: red fescue
 turf. Proc. Northeast. Weed Sci. Soc. 35:331-335.
744                                     P.C. Bhowmlk



  Jagschitz, J.A. 1982. Evaluation of growth retardants in cool-season
  lawn turf. Proc. Northeast. Weed Sci. Soc. 36:334-335.
  Parups, E.V. and Cordukes, W.E. 1977. Growth of turfgrasses as affected
  by artinal and embark. Hort. Sci. 12:258-259.
  Sandbrink, J.J., Kaufman, J.E., Stehling, S.J. and P.S. Thibodeau. 1983.
  Application of Timing of Mon-4620 on cool season grasses. Agron. Abstr.
  pp. 130. 1983 Ann. Meeting of ASA, CSSA and SSSA. Aug. 14-19, 1983.
      Schmidt, R.E. and Bingham, S.W. 1977. Chemical growth regulation of
      "Baron" Kentucky bluegrass. Agron. J. 69:995-1000.
  Watschke, T.L. 1976. Growth regulation of Kentucky bluegrass with
  several growth retardants. Agron. J. 68:787-791.
      Watschke, T.L. 1981. Effect of four growth retardants on two Kentucky
      bluegrass (poa pratensis L.) Proc. Northeast. Weed Sci. Soc.
      35:322-330.
      Welterlen, M.S. and Nash, A.S. 1984. Effects of Mon 4621 and Mon 4623
      on Kentucky bluegrass and tall fescue turf. Proc. Northeast. Weed Sci.
      Soc. 38:307-308.




                                     SUMMARY IN FRENCH

  La reduction     de croissance   et la         suppression   de     l'epiaison    grace    a
  l'utilisation    d'un nouveau reducteur       de croissance.

 On a etudie les effets         de Mon 4621 (liquide)          et de Mon 4622 (granules)
 [Acetamide,      N- ((Acetylamino)      methyl) J      -2-chloro-N-(2,6-diethylphenyl~
 sur la suppression       de l' epiaison     et Ie ralentissement          de la croissance
 du paturin     des pres (Poa pratensis        L.) et de la fetuque rouge (Festuca
 rubra 1.). Les applications           de Mon 4621 et Mon 4622 qui eurent lieu
 Ie3 mai (100 % vert * mais pas de coupe ) ou Ie 12 mai (100 % vert
 * et 2 coupes)        ont ete plus efficaces      quant a la suppression de l'epiai-
 son     (Tabl.l)    que l' application    du 21 mai ( 100 % vert* plus 18 jours
 de croissance       ). Ces effets    furent   observes durant la periode ini tiale
 de 42 jours,      sans tenir compte de la date d'application.              La phytotoxicite
    resultant     de ces traitements       est   minimale        pour Ie gazon dont la
 quali te etai t bonne et meme excellenti'             (Fig.l).    L' application     initiale
 de Mon 4621 a raison          de ~'12 Kg/ha -       sui vie d' une application         de Mon
 4622 a raison       de 2,2 Kg/ha        35 jours plus tard ont redui t la pousse
 pendant 70 jours apres l'application           initiale.(Tabl.2        et 3). La reduction
 de la pousse que ce soi t avec 1 'utilisation              du Mon 4621 ou du Mon 4622
 fut   aussi    efficace,    tout   en creant     moins d'effets          indesirables,      que
 I' application     de mefluidide (N-C2,4-dimethyl-5-        ~p   trifluromethyl     )sulfony~
 amino] phenyl J acetamide] a raison de 0,43 Kg/he . (Fig.l et 2).

				
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