Sugarbeet varieties vary in their response to herbicides. s-Metolachlor and dimethenamid-P were recently registered for use in sugarbeet. Field trials were conducted in Michigan in 2004, 2005, and 2006 to evaluate the response of 12 sugarbeet varieties to s-metolachlor and dimethenamid-P applied PRE and POST to two-leaf and four-leaf stage sugarbeet. s-Metolachlor and dimethenamid-P reduced sugarbeet density when rainfall occurred within 7 d of the PRE applications. Dimethenamid-P PRE caused the most injury across all varieties followed by s-metolachlor PRE. Applying dimethenamid-P POST to two-leaf sugarbeet injured plants more than s-metolachlor applied POST to two- and four-leaf stage sugarbeet. The least amount of sugarbeet injury from dimethenamid-P was from POST applications at the four-leaf stage. Sugarbeet varietal differences were most pronounced from PRE applications of both herbicides and from the POST two-leaf application of dimethenamid-P. Of the 12 sugarbeet varieties evaluated, Hilleshog 2771RZ and Beta 5833R were the most tolerant, whereas Hilleshog 7172RZ was typically the most sensitive variety to these herbicides. Growers will probably not choose varieties based on herbicide tolerance alone, but instead base variety selection on sugar yield and disease resistance. However, if a grower has chosen a particular variety, this information could assist in assessing the risk of using s-metolachlor or dimethenamid-P for weed control.

Nomenclature:Dimethenamid-P; s-metolachlor; sugarbeet, Beta vularis L