Bermudagrass Control with Sequential Applications of Metamifop.

Experiments were conducted at the Plant and Soil Science greenhouse facility in Lubbock, TX. ‘Riviera’ hybrid bermudagrass and ‘Savannah’ common bermudagrass were seeded at 244 kg ha^-1 into pots containing a soilless potting media on August 26, 2011. Pots were allowed to mature in the greenhouse over a three month period. Prior to herbicide application bermudagrass was mowed to 0.6 cm. Herbicides were applied with a CO₂ backpack sprayer equipped with XR8004VS nozzles calibrated to deliver 375 L ha^-1 at 221 kPa. Herbicide treatments were applied on December 1, 2011 and consisted of metamifop at 200, 300, 400, and 500 g ai ha^-1. A sequential application of each treatment was made on December 22, 2011. An untreated check was included for comparison. Visual ratings of percent bermudagrass control was recorded weekly on a scale of 0 (no control) to 100% (completely dead bermudagrass). Pots were cut to 0.6 cm after three weeks of growth (prior to sequential treatments), biomass was dried, and weighed. This procedure was conducted again three weeks after sequential treatments. The non-treated check pots exhibited 0% control and 0.56 to 0.8 g of biomass 3 WAIT, regardless of cultivar. Metamifop at 300 to 500 g ai ha^-1 exhibited 96 to 100% bermudagrass control 3 WAIT, regardless of cultivar. Bermudagrass subjected to those same treatments only exhibited 0.01 to 0.03 g of biomass 3 WAIT, regardless of cultivar. The 200 g ai ha^-1 rate of metamifop exhibited only 8% control of ‘Savannah’ bermudagrass with 0.67 g of biomass collected, while ‘Riviera’ was controlled 36% with 0.36 g of biomass collected. Sequential applications of metamifop at 300 to 500 g ai ha^-1 completely controlled bermudagrass (100%) 6 WAIT, while a sequential application at 200 g ai ha^-1 only controlled bermudagrass 6 to 17% 6 WAIT, regardless of cultivar.