Efficacy of Metamifop for the Control of Large Crabgrass At Various Growth Stages.

Experiments were conducted at the Plant and Soil Science greenhouse facility in Lubbock, TX during the spring of 2012. Large crabgrass [Digitaria sanguinalis (L.) Scop.] was seeded at 12.2 kg ha^-1 into pots (15.2 cm diameter) containing a soilless potting media on March 15, 2012. Greenhouse temperatures were maintained at 34/26 C (day/night) with average midday (1200 and 1300 hr) solar radiation ranging from 636 to 754 µmol m^-2 s^-1. Irrigation was supplied through an overhead irrigation system calibrated to deliver approximately 3.8 cm of water wk^-1.  Pots were maintained at 5.1 cm throughout the length of the trial to simulate the size of crabgrass plants present in an athletic field, home lawn, or golf course rough. Herbicides were applied with a CO₂ backpack sprayer equipped with XR8004VS nozzles calibrated to deliver 375 L ha^-1 at 221 kPa. Metamifop was applied at 200 g ai ha^-1 to large crabgrass plants at three growth stages: 1-2 leaf, 1-2 tiller, and 3-5 tiller. An untreated check was included for comparison. Visual ratings of percent large crabgrass control were recorded weekly on a scale of 0 (no control) to 100% (completely dead crabgrass). Pots were destructively harvested 3 weeks after treatment (WAT), above-ground biomass was dried, and weighed. Large crabgrass that was treated at the 1-2 leaf and 1-2 tiller stage exhibited 100% control and 0 g above-ground biomass 3 WAT. Crabgrass at the 3-5 tiller stage exhibited 96% control and 0.91g above-ground biomass 3 WAT. The non-treated check pots exhibited 0% control and 9.2 g above-ground biomass at the conclusion of the trial. Excellent control of large crabgrass at immature and mature stages was observed in response to single applications of metamifop. This chemistry provides equivalent crabgrass control to quinclorac and may provide an additional alternative to MSMA for grass weed control.