IN THIS SECTION

PRODUCTION COSTS YIELD LOSS MORE APPLICATIONS REACTIVE MANAGEMENT

Some weeds are more competitive with the crop and among those are weeds that are more likely to develop weed resistance, such as Amaranthus species.

Waterhemp ¹
In corn, 1 uncontrolled weed per square yard cuts yield 7.5 bushels per acre. In soybeans, 1 uncontrolled weed per square yard cuts yield up to 15 bushels per acre.


Redroot pigweed ²
Just 2 weeds per square meter — about the area of a hula hoop — caused a 15.6 percent yield loss in soybeans.


Lambsquarters ³
At a density of 2 weeds per foot of row, lambsquarters decreased corn yields by 11 percent.

Uncontrolled weeds compete with the crop longer. An Ohio State University study evaluated the cost of weed competition on yield in corn. The University of Nebraska determined the cost of yield competition in soybeans.

Corn ⁴

• At 4 inch weed height, average corn yield loss, when compared to the weed-free check, was 6 percent.
• If herbicides were applied when weeds reached 12 inches, a 21 percent yield loss would result.

Soybeans ⁵

• Depending on row spacing, weeds should be controlled between stages V1 and V3.
• Two percent yield loss per leaf stage past critical period through R3.

¹ Hypothetical values modeled by WeedSOFT,® a computer module designed by university weed scientists.
² “How Much Are Herbicide Resistant Weeds Costing You?” Ontario Ministry of Agriculture, Food and Rural Affairs.
³ “Variations in Corn Yield Losses Due to Weed Competition.” M. Moechnig et. University of Wisconsin — Madison. March 2000.
⁴ Average yield loss across 35 trials in the Corn Belt. Data summarized by S. Gower and M. Loux, Ohio State University.
⁵ Knezevic, S.Z., Evans, S.P., Mainz, M. 2003. Yield Penalty Due to Weed Control in Corn and Soybeans, Online. Crop Management doi: 10.1094/CM-2003-0219-01-RS.