Abstract
Two herbicide experiments on pumpkin were conducted in a San Antón loam at Fortuna substation from 1989 to 1990 to evaluate clomazone, chloramben, DCPA, metolachar and certain sequential combinations. In the first experiment, clomazone at 1.12 and 2.24 kg ai/ha applied preplant gave excellent control of most grasses. Chloramben at 4.48 kg ai/ha provided only fair weed control. Chloramben in sequential application with bentazon + fluazifop mixture greatly improved weed control. DCPA at 11.2 kg ai/ha controlled weed slightly better than chloramben, DCPA in sequential application with bentazon + fluazifop mixture also improved weed control. The highest pumpkin yield was obtained with the weeded check, which was significantly superior to all herbicide treatments. There were no significant yield differences among the herbicide treatments. In the second experiment, the best weed control treatment was clomazone at 2.24 kg ai/ha applied as pre-plant + sequential application of paraquat at 0.56 kg ai/ha. Metolachor at 2.24 and 4.48 kg ai/ha gave good grass control (80-93%), but only fair (46-70%) on broad leaf weeds. Chloramben at 4.48 kg ai/ha only fairly controlled weeds. DCPA at 11.2 kg ai/ha gave good grass control, but was weak on broadleaf weeds. Chloramben or DCPA in sequential application with paraquat at the rate of 0.56 kg ai/ha controlled weeds better than either used alone. The highest pumpkin yield was obtained with clomazone at 2.24 kg ai/ha + paraquat at 0.56 kg at/ha, followed by the weeded check and clomazone at 1.12 kg ai/ha. These three treaments differed significantly from the four remaining herbicide treatments.