Weed management in sweet corn and other rotational crops (2007)

Report to the Oregon Processed Vegetable Commission

Ed Peachey
OSU Dept. of Horticulture


  • Impact and Laudis herbicides were evaluated for wild proso millet and broadleaf weed control in sweet corn.
  • The most effective treatments were Impact and Laudis applied with Outlook and atrazine at V2-3.
  • Increasing the methylated seed oil (MSO) rate from 0.25% to 1 % was more important for improving weed control efficacy than adding UAN (Figure 1).
  • Impact + Outlook + atrazine (Tr. 14) provided yields above 11 t/A with exceptional wild proso millet control (Table 2).
  • Predicting the optimum rate of atrazine to use with these herbicides will be difficult if the objective is optimizing yield. The data suggest that a tankmix of both 2 lbs/A or none will give the same yield of sweet corn when there is a high density of both wild proso millet and broadleaves.
  • The symptoms normally associated with Impact injury (bleaching) have not been observed on crops planted in the fall or spring following sweet corn. Crop stand and yield may have been reduced in a few sensitive crops such as table beets. However, this only occurred at the 2x rate. There is very little risk of crop injury caused by Impact herbicide carryover.
  • Insecticides reduced the activity and density of the ground beetle P. melanarius from 2.0 beetles to 0.3 in the strip-till plots and from 1.5 to 0.2 beetles in conventional tillage. There was no effect of the tillage systems on beetle activity-density.
  • Seed loss due to predation by ground beetles averaged 20% during the month of August. Predation of wild proso millet seeds was influenced by the tillage-insecticide treatments. Insecticide use was the most important factor regulating predation of wild proso millet.