Optimizing S-metolachlor and dimethenamid-P in sugarbeet microrate treatments.

摘要

Field trials were conducted in East Lansing in 2004 and 2005 and in St. Charles, Michigan, USA, in 2004, 2005 and 2006 to compare weed control and sugarbeet tolerance from microrate herbicide treatments that included S-metolachlor and dimethenamid-P. Treatments included the base microrate treatment alone and with full- and split-application rates of S-metolachlor at 1.4 kg/ha or dimethenamid-P at 0.84 kg/ha at the various microrate application timings. All the treatments caused injuries to sugarbeet. In 2004 and 2006, full rates of both S-metolachlor and dimethenamid-P applied pre-emergence (PRE) or in the first microrate application injured sugarbeet more than the base microrate treatment. When S-metolachlor or dimethenamid-P were split-applied between PRE and the third microrate application or between the first and the third microrate applications, injury was still greater than from the base microrate treatment. Furthermore, applying dimethenamid-P at one-fourth the full rate in all four microrate applications injured sugarbeet more than the base microrate treatment. A full rate of S-metolachlor or dimethenamid-P applied in either the third or fourth microrate applications or splitting the applications between the second and fourth microrate treatments did not increase sugarbeet injury compared with the base microrate treatment. Control of common lambsquarters (Chenopodium album) and giant foxtail (Setaria faberi) from all treatments containing S-metolachlor or dimethenamid-P, regardless of the time of application, was greater than from the base microrate treatment at all locations. Pigweed species control was 94 or greater from all treatments. In 2004, late-season control of giant foxtail was greater from all treatments that included S-metolachlor or dimethenamid-P compared with the base microrate treatment. In 2005, the only treatments that did not improve late-season giant foxtail control compared with the base microrate treatment were the treatments that included a full rate of S-metolachlor or dimethenamid-P applied in the fourth microrate application. Even though some herbicide treatments that included S-metolachlor or dimethenamid-P injured sugarbeet more than the base microrate treatment, recoverable sucrose per hectare was similar among treatments.