Efficacy of experimental herbicide products

Plots were located in turf research area at the Guelph Turfgrass Institute, Guelph, ON. The site was an area of established turf (predominantly turf-type perennial ryegrass, infested with dandelion, clover and other lawn weeds) (Figure 1). Turf was maintained with typical medium maintenance turf regime: 1.0 kg actual N 100 m-2 per year in 3 applications (spring, summer, dormant); P and K in a 4:1:4 ratio with N; irrigated to prevent stress prior to treatment application and to prevent dormancy thereafter; mowed at 3 inches. The treatments were combinations of different rates and volumes of post-emergent herbicide, as well as controls for a total of 14 treatments. Plots were rated pre-treatment for weed presence by visual ratings of broadleaf weed density and point quadrat measurement of weed cover. All of the treatments were phytotoxic to both weeds and grass, with SC2 and VNT-3 being particularly phytotoxic. Both grass and weeds recovered from the phytotoxic effects by 5 weeks after treatment. Watering treatments in with 10 mm of water immediately after application reduced the phytotoxic effects in the two treatments where it was tested.