Reduced herbicide rates for large crabgrass (Digitaria sanguinalis) and goosegrass (Eleusine indica) control in bermudagrass (Cynodon dactylon)

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Five PRE herbicides were applied at below maximum registered use rates to the same bermudagrass turf plots for three consecutive years for large crabgrass and goosegrass control. In most instances, full labeled herbicide rates were needed for acceptable large crabgrass and goosegrass control during the 1st year of treatment. All herbicides controlled large crabgrass but not goosegrass during the 1st year. Weed management programs that utilized the lowest herbicide rates while maintaining ≥ 80% control during the 2nd and 3rd years varied with herbicides. The programs for large crabgrass were prodiamine at 0.8 kg ha−1the 1st year followed by 0.2 kg ha−1the 2nd and 3rd years; oryzalin at 2.2 kg ha−1the 1st year followed by 0.6 kg ha−1the 2nd and 3rd years; dithiopyr at 0.3 kg ha−1the 1st year followed by 0.1 kg ha−1the 2nd and 3rd years; pendimethalin at 1.7 kg ha−1the 1st year followed by 0.8 kg ha−1the 2nd and 3rd years; and oxadiazon at 3.4 kg hha−1the 1st year followed by 2.5 kg ha−1the 2nd year and 1.7 kg ha−1the 3rd year. The programs for goosegrass were prodiamine at 0.8 kg ha−1followed by 0.6 kg ha−1the 2nd and 0.4 kg ha−1the 3rd year; dithiopyr at 0.8 kg ha−1the 1st year followed by 0.4 kg ha−1the 2nd and 3rd years; pendimethalin at 3.4 kg ha−1the 1st year followed by 1.7 kg ha−1the 2nd year and 0.8 kg ha−1the 3rd year; and oxadiazon at 3.4 kg ha−1followed by 0.8 kg ha−1the 2nd and 3rd years. Because goosegrass control with oryzalin at reduced rates was unacceptable during the 1st and 2nd years, this herbicide should not be used in a reduced rate program. The quality of common bermudagrass was not affected by reduced herbicide rates.