Waterhemp is particularly difficult to control because of its evolved resistance to several herbicide classes. When the worst-weed rankings for corn are compared according to their difficulty to control, waterhemp is consistently ranked as the worst.
Giant ragweed has developed glyphosate resistance in some areas and is therefore very difficult to control. This weed is commonly ranked as the second hardest to control, behind waterhemp.
Marestail has developed glyphosate resistance and can be a problem in no-till fields. Non-glyphosate-resistant marestail can also reduce corn yields quickly when in high density.
Foxtail is the most common grass weed that competes with corn in Illinois. It is also widespread across Iowa. Early-season competition from this weed can reduce corn yields if postemergence applications are not timely.
Velvetleaf is particularly prevalent in cornfields across Nebraska. It is difficult to control because of its competitiveness, prevalence and longevity of seed in the soil.
Before deciding which control products to use for the next season, you must identify the predominant weed species for each field. These are the top worst weeds that can be found in cornfields.
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