Controlling early season weeds is critical to achieving high corn yields. Weeds can reduce corn yields as early as the V2 stage.
Soil-applied herbicides require light incorporation or rainfall within 5 to 7 days of application. Lack of rainfall, uneven incorporation or excess rainfall can dramatically reduce herbicide performance and yield.
A preemergent herbicide followed by a postemergence herbicide program is the most reliable and effective weed control program. Preemergence or postemergence only herbicide programs can protect yield equally to a 2-pass program but they require careful management.
The study below compares weed competition in a total post-herbicide program. The highest level of weed control was achieved by delaying the postemergence herbicide application until weeds were 12 inches tall. However, yield loss due to weed competition was nearly 3 times greater compared to when weeds were controlled when they were 2 to 6 inches tall.