Tropical Signalgrass (Urochloa subquadripara) Control with Preemergence- and Postemergence-Applied Herbicides

Abstract

Tropical signalgrass is one of the most serious weed problems in the St. Augustinegrass sod production in Florida, and its presence increases production costs and lowers turfgrass quality. The objectives of our research were to: (1) evaluate herbicides preemergence and postemergence for control of tropical signalgrass and (2) compare control of tropical signalgrass and other problem weeds (torpedograss, blanket crabgrass, and India crabgrass) with postemergence herbicides. In preemergence herbicide field trials, only benefin + oryzalin, imazapic, imazapic + 2,4-D, and oryzalin provided ≥75% tropical signalgrass control 8 wk after application (WAA). By 11 WAA, only benefin + oryzalin and imazapic + 2,4-D provided ≥75% tropical signalgrass control. In greenhouse experiments, eight herbicide treatments were applied postemergence to tropical signalgrass seedlings at the two-, four-, six-, and eight-leaf stages. Asulam and CGA 362622 provided ≥89% tropical signalgrass control at all application timings. Imazaquin controlled tropical signalgrass ≥98% when applied before the eight-leaf stage. However, in field trials with mature tropical signalgrass (>20 cm stolons), none of the 20 herbicide treatments applied postemergence provided acceptable control.

Nuevos xenófitos de La Palma (Islas Canarias, España), con énfasis en las especies naturalizadas y (potencialmente) invasoras. Parte 3

“…It is reported as a troublesome weed and is also cultivated in some parts of the tropics as forage because of its drought tolerance. According to Teuton et al (2004) it is "one of the most serious weed problems in the St. Augustine grass sod production in Florida and its presence increases production costs and lowers turfgrass quality".…”

Prediction Modeling for Tropical Signalgrass (Urochloa subquadripara ) Emergence in Florida

“…Weekly mean temperatures were calculated beginning on the first day of January. Kriging interpolation method (4) was used to predict weekly mean air temperature values for entire state using 103 sample points. A semi‐variorum was used to determine the range, partial sill, and nugget values (parameters required for this GIS method) for weekly temperature means.…”

“…Tropical signalgrass is a dominant weed in the St. Augustinegrass industry of Florida and is potentially troublesome from movement with St. Augustine sod and mechanical seed dissemination. Tropical signalgrass tolerates most selective postemergence herbicides labeled for application to St. Augustinegrass (4). Preemergence herbicide options such as oryzalin or benefin + oryzalin control tropical signalgrass for 8 to 11 weeks after treatment (4).…”

“…In Florida, the majority of tropical signalgrass can be found south of U.S. Interstate Highway 4 (latitude 28°N). Tropical signalgrass usually does not perenniate north of US Interstate Highway 4 due to killing freezes (4); however, annual re‐infestation from seed is common in these areas. In our previous research, tropical signalgrass emergence was observed when weekly mean soil or ambient air temperatures were ≥ 20°C (3).…”

“…Tropical signalgrass tolerates most selective postemergence herbicides labeled for application to St. Augustinegrass (4). Preemergence herbicide options such as oryzalin or benefin + oryzalin control tropical signalgrass for 8 to 11 weeks after treatment (4).…”