Tolerance of Seedling Bermudagrass to Postemergence Herbicides

Abstract

The introduction of improved seeded cultivars of bermudagrass [Cynodon dactylon (L.) Pers.] has generated significant interest from the turfgrass industry. An important component of successfully establishing these new cultivars will be to develop effective weed control strategies for the critical establishment period. A field study and a greenhouse study were conducted to evaluate the tolerance of several seeded bermudagrasses to commonly used postemergence herbicides at different periods of establishment. In a field study, ‘Princess’ bermudagrass was seeded at a rate of 48 kg ha−1 during the early summer of 2000 and 2001. Postemergence herbicides were applied at either 1, 2, or 4 wk after emergence (WAE). Herbicide treatments included MSMA (monosodium salt of methylarsonic acid) at 1.12 kg ha−1, metsulfuron (2[[[[(4‐methoxy‐6‐methyl‐1,3,5‐triazin‐2yl] amino] carboxyl] amino] sulfonyl]‐2‐benzoic acid) at 0.021 kg ha−1, diclofop ((±)‐2‐[4‐(2,4‐dichlorophenoxy) phenoxy]propanoic acid) at 1.12 kg ha−1, clopyralid (3,6 dichloro‐2‐pyridinecarboxylic acid) at 0.56 kg ha−1, dicamba (3,6‐dichloro‐2‐methoxybenzoic acid) at 0.56 kg ha−1, 2,4‐D amine D [(2,4‐ dichlorophenoxy) acetic acid at 0.56 kg ha−1, and quinclorac (3, 7‐dichloro‐8‐quinolinecarboxylic acid) at 0.842 kg ha−1 Visual injury ratings were recorded at 3, 5, 7, 15, and 30 d after treatment (DAT) and percent turfgrass cover was recorded at 30 and 60 DAT. In the greenhouse study, the same herbicides and treatments were used with the cultivars Princess, Yukon, NuMex Sahara, Jackpot, and Mirage. In both the field and greenhouse studies, there was no clear effect of application timing on the tolerance of seedling bermudagrass to herbicides. Diclofop and metsulfuron caused the highest levels of injury in both years of the field study and in the greenhouse study. The other herbicides tested caused less injury. The bermudagrass recovered from all herbicide injury by 30 d after treatment. The results from this study indicate that seedling bermudagrass is relatively tolerant of many commonly used postemergence herbicides as soon as 1 WAE. These results will be useful to turfgrass managers who are considering use of improved cultivars in various turf situations.

Tolerance of ‘Riviera’ Bermudagrass to MSMA Tank-Mixtures with Postemergence Herbicides During Establishment from Seed

“…For those herbicides that are used to control grassy weeds, quinclorac had good safety on seedling bermudagrass (Figs. 1 through 4), which is in agreement with earlier reports (6,8,11). When quinclorac was tank‐mixed with MSMA, herbicide injury was increased (Fig.…”

“…4). Earlier trials at this location with metsulfuron revealed similar results on this and other seeded bermudagrass cultivars (6). Foramsulfuron and trifloxysulfuron were tested in a previous trial against four seeded bermudagrass cultivars, including ‘Riviera,’ and found to have good safety when applied at 4 to 7 weeks after emergence (8).…”

“…Most of the broadleaf herbicides tested in this trial and by other researchers (6,8) appear to have relatively good safety on seeded bermudagrass during establishment. Quinclorac also has good activity on numerous broadleaf weeds and has excellent safety on seedling bermudagrass (6,8,11). Therefore, a number of herbicide combinations are available to control both annual and perennial broadleaf weeds during the establishment of seeded bermudagrass.…”

“…However, quinclorac (3, 7‐dichloro‐8‐quinolinecarboxylic acid) is the only postemergence herbicide that is labeled for use during seedling establishment of bermudagrass and previous studies have confirmed its safety (6,8). Recently, the safety of other postemergence herbicides on seedling bermudagrass has also been investigated in an attempt to broaden the spectrum of herbicides available for use during establishment of these grasses (6,8). Of the herbicides tested in those studies, MSMA (monosodium salt of methylarsonic acid) had good safety on seedling bermudagrass (6) and is an effective herbicide for controlling problematic, grassy weeds such as crabgrass.…”

“…Recently, the safety of other postemergence herbicides on seedling bermudagrass has also been investigated in an attempt to broaden the spectrum of herbicides available for use during establishment of these grasses (6,8). Of the herbicides tested in those studies, MSMA (monosodium salt of methylarsonic acid) had good safety on seedling bermudagrass (6) and is an effective herbicide for controlling problematic, grassy weeds such as crabgrass. However, label recommendations for this product state that it is not to be used on seedling turfgrass until the turf has been mown three times.…”