Saturday, March 3, 2012

Planning for Critical Weed Control

Each year, we are busy managing our crops. Sometimes we delay post-emergence weed control trying to get the most weed control during a spray application. However the cost of delaying weed control costs yield.
There are critical stages in the growth of corn and soybean where weeds do not significant hurt yield before or after these time periods. Critical timing in corn is often at high nitrogen rates, between the 6th and 9th leaf stage of corn. If you are using lower nitrogen rates, then the leaf stage may be lowered so it is from the 4th to 9th leaf stage.
As for soybean, the critical weed stage is the first trifoliate stage in 30-inch rows whereas in 15-inch rows it was the second trifoliate. This implies that weed control should begin earlier in wide rows than narrow rows.
Delaying weed control beyond the start of the identified period for weed control will cost the grower an average of 2 percent yield loss for everyone leaf stage delay in corn and also in soybean according to University Nebraska weed research data.
As you make your spring herbicide plans, don’t forget to apply pre-emergence products to manage glyphosate weed resistance and be sure to apply your post-emergence products at the proper time to prevent yield loss.
For more information, contact Wayne Flanary at 660-446-3724 or Heather Benedict at 660-425-6434, Regional Agronomists, University of Missouri Extension.

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