Integrated Crop Management

Options for weed control in large corn

The ongoing wet weather prevented many cornfields from being treated with planned postmergence treatments. The growth of corn during this period has eliminated many of the herbicide options that were planned for these fields. Table 1 shows products cleared for use on corn larger than 12 inches in height. Keep in mind that just because a product is labeled for use in large corn does not mean it will control large weeds that may be present in these fields. Also, the risk of crop injury increases with corn size for many products, especially when the corn is under stress. Before deciding to treat large corn, consider the impact of the weeds on the crop if they are left untreated, the likelihood of achieving good weed control, and the potential for crop injury. Equipping the sprayer with drop nozzles reduces the potential for crop injury and provides better weed control.

Table 1. Herbicides cleared for use on corn larger than 12 inches in height.

Product

sizea
Maximum corn Comments
Accent 36 inches Use drop nozzles on corn 20 to 36 inches in height or 10 collars
Aim 8 leaf

collars
Good on large velvetleaf.
Banvel 36 inches Use directed application when 1) corn leaves prevent proper spray coverage, 2) sensitive crops are grown nearby, or 3) tank mixing with 2,4-D. Should not be applied to corn greater than 24 inches if soybean is grown in the area.
Basagran none Basagran is a contact herbicide that generally does not control large weeds.
Buctril tasseling Buctril is a contact herbicide that generally does not control large weeds.
Callisto 30 inches

or 8 leaves
Labeled for weeds 5 inches or less in height.
Celebrity

Plus
24 inches Combination of Accent and Distinct.
Clarity 36 inches Use directed application when canopy prevents spray coverage.
Distinct 24 inches Use 4-ounce rate. Contains dicamba.
Hornet 36 inches Drop nozzles must be used on corn 20 to 36 inches in height or with more than six collars.
Liberty 36 inches Requires Liberty-Link corn. Use drop nozzles on corn 24 to 36 inches in height.
Lightning 45 days

before harvest
Requires IMI-corn. Drop nozzles must be used on corn taller than 20 inches.
Permit layby Refer to label for maximum weed heights controlled.
Resource 10 leaf Good on large velvetleaf. Use drop nozzles when corn leaves interfere with spray penetration.
Roundup

Ultra
eight leaves or 30 inches Requires Roundup-Ready corn.
Sencor depends on

tank mix

partner
Sencor can be tank mixed with the following products at rates of 1.6 to 3.0 ounces:

with Basagran: 30-inch corn

with Banvel: Use drop nozzles on corn 8-36 inches in height

with Buctril: Apply before corn canopy closes over row

with Resource: Up to 10-leaf corn

with Tough: Up to 30-inch corn.
Tough 68 days

before harvest
Tough is a contact herbicide that generally does not control large weeds.
2,4-D

amine
tasseling Use drop nozzles on corn greater than 8 inches. Product labels may vary.
2,4-D

ester
tasseling Use drop nozzles on corn greater than 8 inches. Product labels may vary.

aThere is no standardized system of specifying crop stage within the herbicide industry, thus resulting in a variety of descriptions for label restrictions.

This article originally appeared on page 123 of the IC-486(15) -- June 25, 2001 issue.


Source URL:
http://www.ipm.iastate.edu/ipm/icm//ipm/icm/2001/6-25-2001/weedcontr.html