Synthetic auxins are popular herbicides for selective, postemergence broadleaf weed control in turfgrass management (Struckmeyer, 1951; Watson, 1950). Herbicides in this class of chemistry control susceptible weeds by disrupting hormonal balance leading to increased cell wall plasticity, nucleic acid metabolism, and uncontrolled growth in meristimatic regions (Sterling and Hall, 1997). A new synthetic auxin, aminocyclopyrachlor, was registered in 2010 for annual and perennial broadleaf weed control in turfgrass (Anonymous, 2010).
Aminocyclopyrachlor is the first pyrimidine carboxylic acid herbicide with structural similarities to pyridines (Bukum et al., 2010). This herbicide has both foliar and soil activity and is more effective at lower rates than 2,4-D and other auxin herbicides (Flessner et al., 2011; Turner et al., 2009). Aminocyclopyrachlor has efficacy on many broadleaf weed species including wild carrot (Daucus carota L.) Canada thistle [Cirsium arvense (L.) Scop.], Japanese knotweed (Fallopia japonica Houtt.), catsear dandelion (Hypochoeris radicata L.), and plantains (Plantago spp.) (Anonymous, 2010; Bukum et al., 2010; Curtis et al., 2009; Rudenko, 2009).
Aminocyclopyachlor has promising implications for controlling problematic broadleaf weeds in turfgrass, but turfgrass managers may want to re-establish cool-season grasses from seed after applications. Application timing and rate of postemergence herbicides from various herbicide families have been reported to inhibit establishment of cool- and warm-season turfgrasses from seed. Prepackage products that include auxin herbicides 2,4-D, dicamba, and MCPP are recommended to be applied 3 to 4 weeks before seed is sown or after two to three mowing events (Anonymous, 2004). Quinclorac, a highly selective auxin herbicide, has shown to be safe when applied at seeding of annual bluegrass (Poa annua L.), tall fescue (Festuca arundinacea Schreb.), perennial ryegrass (Lolium perenne L.), and fine fescue for pre-weed control during establishment (Anonymous, 1998; Enache and Ilnicki, 1991). Reicher et al. (1999) found that quinclorac at 0.84 kg·ha−1 did not injure kentucky bluegrass (Poa pratensis L.) or perennial ryegrass when applied at seeding. These experiments did note that quinclorac applied at seeding delayed the cover of kentucky bluegrass up to 16 weeks (Reicher et al., 1999). Bispyribac sodium applied 1 week before seeding (WBS) reduced creeping bentgrass (Agrostis stolonifera L.) and kentucky bluegrass by 30% and 42% compared with the non-treated control, respectively. However, these grasses were safely established when bispyribac sodium was applied 2 WBS (Lycan and Hart, 2006). Sulfosulfuron at 13 to 26 g/a.i./ha applied the day of seeding or 1 WBS reduced creeping bentgrass and kentucky bluegrass establishment compared with the non-treated control (McCullough and Nutt, 2010; Willis et al., 2007). Amicarbazone applied at 0.4 kg·ha−1 has the potential to reduce perennial ryegrass and tall fescue cover when applied the day of seeding. However, researchers noted that perennial ryegrass and tall fescue establishment appears uninhibited when amicarbazone at the same rate is applied 2, 4, or 6 WBS (McCullough et al., 2011). Common bermudagrass [Cynodon dactylon (L.) Pers.] seedlings have shown significant injury and reduced establishment in response to rimsulfuron, simazine, and trifloxysulfuron applied 1 to 2 WBS (McCullough and Nutt, 2010; Willis et al., 2007). McCalla et al. (2004) reported that ‘Princess 77’ bermudagrass seedlings exhibited 30% or less injury after applications of diclofop, metsulfuron, 2,4-D, dicamba, monosodium acid methanearsonate (MSMA), clopyralid, and quinclorac applied 1, 2, and 4 weeks after emergence. McElroy et al. (2005) noted that prepackaged mixtures of herbicides containing 2,4-D, mecoprop, dicamba, clopyralid, or triclopyr should be used with caution when applied at seeding or before stolon development with warm-season grasses. The researchers found that low and high rates of 2,4-D + mecoprop + dicamba and 2,4-D + clopyralid + dicamba reduced bermudagrass cover of the cultivars Yukon, Riviera, and Princess 7 21 d after initial treatment when compared with the non-treated control (McElroy et al., 2005).
Turfgrass managers may need to reseed desirable turfgrasses like perennial ryegrass and tall fescue after broadleaf weeds have been controlled by aminocyclopyrachlor or other postemergence herbicides. Thus, reseeding intervals may be critical for new herbicides introduced for postemergence broadleaf weed control in turf management regimes. Data describing reseeding intervals after aminocyclopyrachlor treatments are limited. In the transition zone and cool humid region of the United States, tall fescue and perennial ryegrass are widely used for residential lawns, golf courses, and commercial properties. The objective of this research was to determine reseeding intervals for perennial ryegrass and tall fescue after aminocyclopyachlor applications.
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