Optimizings-Metolachlor and Dimethenamid-P in Sugarbeet Microrate Treatments

Abstract

Field trials were conducted in East Lansing, MI in 2004 and 2005 and in St. Charles, MI in 2004, 2005, and 2006 to compare weed control and sugarbeet tolerance from microrate herbicide treatments that includeds-metolachlor and dimethenamid-P. Treatments included the base microrate treatment alone and with full- and split-application rates ofs-metolachlor at 1.4 kg/ha or dimethenamid-P at 0.84 kg/ha at the various microrate application timings. All treatments injured sugarbeet. In 2004 and 2006, full rates of boths-metolachlor and dimethenamid-P applied PRE or in the first microrate application injured sugarbeet more than the base microrate treatment. Whens-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 ofs-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 and giant foxtail from all treatments containings-metolachlor or dimethenamid-P, regardless of the time of application, was greater than from the base microrate treatment at all locations. Pigweed spp. control was 94% or greater from all treatments. In 2004, late-season control of giant foxtail was greater from all treatments that includeds-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 ofs-metolachlor or dimethenamid-P applied in the fourth microrate application. Even though some herbicide treatments that includeds-metolachlor or dimethenamid-P injured sugarbeet more than the base microrate treatment, recoverable sucrose per hectare was similar among treatments.