The Effects of Various Scalping Timings on Tall Fescue Control with Glyphosate.

Herbicides containing glyphosate are commonly used during renovations, or to control difficult weeds. Users commonly scalp treated areas to sow desirable species following treatment, and most product labels recommend withholding mowing for several days before or after an application for maximum efficacy. Our objective was to determine the effects of various scalping timings on glyphosate efficacy. Tall fescue (Schedonorus arundinaceus [Schreb.] Dumort.) mowed at 7.6 cm was treated with glyphosate at 3.4 kg a.i. ha^-1 and scalped one day or one hour before treatment, or one hour or one to five days after treatment in Mead, NE and Manhattan, KS in fall 2016 and spring 2017. Green cover of tall fescue was rated until 32 weeks after treatment (WAT). After treatment in fall 2016 in Nebraska, all treatments except scalping one hour after treatment completely controlled tall fescue 32 WAT. Scalping one hour following treatment resulted in 67% green cover of tall fescue 32 WAT, not different from untreated plots (97% green cover of tall fescue). In Kansas, untreated plots and plots scalped one day or one hour before treatment, or one hour after treatment had similar tall fescue cover at 32 WAT. All other scalping timings reduced tall fescue cover compared to the untreated by 32 WAT. Scalping four or five days after treatment with glyphosate resulted in complete control of tall fescue 32 WAT, and scalping one, two, or three days after treatment were not significantly different (8, 1, or 3% green cover of tall fescue, respectively). Results from spring applications yielded similar results. Preliminary results indicate that tall fescue control with glyphosate is not adversely affected by scalping as soon as one day following treatment, sooner than previously recommended. Further, scalping turf immediately after an accidental application of glyphosate may be a good strategy to mitigate injury.