Chemical Regulation of Grass Growth. I. Field and Greenhouse Studies with Tall Fescue¹

Abstract

Growth control of grass and other vegetation has been achieved on a limited scale by the use of chemical retardants on highway roadbanks and similar rough turfgrass areas. A few chemical growth retardants are available commercially and a number of experimental chemicals have been developed recently. Five greenhouse experiments and four field studies were conducted from 1970 to 1972 at Southern Illinois University to evaluate commercial and experimental chemical retardants on ‘Kentucky 31’ tall fescue (Festuca arundinacea Schreb.), one of the leading grasses used in Illinois for roadbank stabilization. Nineteen chemicals or formulations were tested with potted tall fescue in the greenhouse and several rates of eight different chemicals were evaluated under field conditions. On selected dates after treatment, grass plots were evaluated as to height, color maintenance, stand losses, and weed infestations. In greenhouse trials the most promising results were obtained with Slo‐Gro, a maleic hydrazide (MH) formulation [diethanolamine salt of 6‐hydroxy‐3‐(2H)‐pyridazinone]; MON‐820 (N‐phosphonomethylimino‐diacetic acid); MON‐845 [N,N‐Bis(phosphonomethyl)glycine]; MBR‐6033 (3‐trifluoromethyl‐ sulfonamido‐p‐acetotoluidide); and Maintain CF‐125 (methyl‐2‐chloro‐9‐hydroxyfluorene‐9‐carboxylate, methyl‐9‐hydroxyfluorene‐9‐carboxylate, methyl‐2, 7 dichloro‐9‐hydroxyfiuorene‐9‐carboxylate). MBR‐6033 showed considerable potential in providing balanced control of growth while enhancing or maintaining a desirable green color. Sustaining color was difficult with other chemicals evaluated when used at rates sufficient to reduce growth over a long time interval. MON‐820, MON‐845, Slo‐Gro (MH), and Maintain CF‐125 reduced grass growth and dry matter yield markedly at selected rates in field studies. However, color deterioration, stand reduction, and weed infestation were serious at higher chemical rates. MON‐814 (ethanolamine‐p‐nitrobenzene‐sulfonylurea), MON‐139 (phosphonomethylglycine, isopropyl‐ammonium salt), and MON‐464 (phosphonomethylglycine, calcium salt) were less consistent in reducing growth while sustaining color. Slo‐Gro, MBR‐6033, and Maintain CF‐125 effectively suppressed tall fescue seedhead development. Information gained from these studies indicates that treatment with selected commercial and experimental growth retardant chemicals can result in effective tall fescue growth control and seedhead suppression. In some instances, chemical treatment of grass resulted in some degree of phytotoxicity and grass color losses. A notable exception was treatment with MBR‐6033 (Sustar), which gave good growth control while maintaining or enhancing grass color.

Tall Fescue Sward Response to Mefluidide and Nitrogen1

“…The interaction between mefluidide and N may be attributable to the promotion of tillering by N when mefluidide diminished the level of apical dominance and increased the level of non-structural carbohydrates in the tillers ( 1 0). 3 At the third harvest in 1979, dry matter yields of plots receiving 80 kg N ha-1 were 22, 27, and 49% higher than plots receiving no mefluidide when mefluidide was applied on 29 March, 15 May, and on both dates, respectively (Table 6). When no N was applied there were no significant differences between mefluidide treatments.…”

“…In addition, total nonstructural carbohydrates tend to accumulate in grasses following mefluidide treatment (11), further promoting tillering (6). 3 Application of 30 kg N ha -I resulted in significantly higher leaf dry weight and leaf area tiller-1 in 1979 (Table 4). Although mean tiller weight tended to be higher when N was applied, the higher dry matter yields (Table 6) associated with N applications were mainly because of its effect on tiller population.…”

“…These responses would agree with reports that mefluidide acts as an inhibitor of IAA metabolism. 3 Tiller growth was also altered by the 14 Mar. 1980 application of mefluidide (Table 3).…”

“…Improved forage quality of tall fescue has been reported following the application of mefluidide at 0.20 to 0.56 kg ha-1 (4, 8). 3 Glenn (4) also reported reduction in cellulose content and elevation of crude protein level, up to 21 o/o. 3 This investigation was undertaken to examine the response of established tall fescue swards to timing of mefluidide application and rate and timing of N fertilization.…”

“…Establishment of vigorous legume stands requires destruction or suppression of existing vegetation to minimize competition for light, soil water, and plant nutrients (2). Mefluidide (N- [2,4-dimethyl-5 [[(trifluoromethyl)sulfonyl]amino]phenyl]acetamide) has been used for height control and seedhead suppression in coolseason turf grasses (3,7,11,12); however, its potential as a grass suppressant for pasture renovation has only recently been examined (8).…”