Torpedograss (Panicum repensL.) control with lower rates of glyphosate

Abstract

Abstract The effect of glyphosate [N‐(phosphonomethyl) glycine] applied as foliar sprays, on the shoot growth, regrowth from ‘crown’ and rhizome bud‐viability of perennial torpedograss (Panicum repens L.) was studied. In general, rates of 1.0–4.0 kg a.i./ha killed 80–100% of aerial shoots and suppressed 90–100% of regrowth from treated plants. Rates above 1.0 kg a.i./ha also killed 80–97% of rhizome buds within 7 days of spraying. Rates below 1.0 kg/ha gave insufficient regrowth suppression and bud‐ kill and were not adequate to control well‐established, mature plants. Plant age was a factor which affected glyphosate control of the weed, and while the young plants under 8 weeks of age were effectively killed by lower rates, the killing of older plants up to 20 weeks of age required rates above 1.0 kg/ha. Although rhizome length was not a major factor influencing the killing of rhizome buds by a range of rates of 0.5–4.0 kg/ha, the results of several experiments indicated that a rate close to 4.0 kg/ha was...