Options for delayed herbicide applications

As wet weather continues to delay fieldwork across the state, some fields of corn have emerged before the planned preemergence herbicide could be applied. Last week's ICM article on weed management discussed the effectiveness of delayed preemergence applications. Listed below are the herbicides that allow for delayed-preemergence or early-postemergence applications. Be sure to consult product labels to determine specific restrictions concerning delayed-preemergence applications or when tank-mixtures are used.

Remember that these products primarily control weeds before they emerge and will have little or no effect on weeds already present in the field. If large populations of weeds have already emerged, a postemergence product may be necessary along with the preemergence herbicide. Consult the labels of each product involved before using any tankmix.

It is also important to note that when these products are applied after corn emergence only water can be used as a carrier.

Product Delayed preemergence options
Atrazine Apply before corn reaches 12" in height and weeds reach 1.5" in height.
Bicep II, Bicep Lite II, Bicep II Magnum, Bicep Lite II Magnum Broadcast--apply before corn exceeds 5" in height or the weeds pass the 2-leaf stage. Directed--apply before corn exceeds 12" in height or the weeds pass the 2-leaf stage. Minimize contact with corn leaves.
Bladex 90DF, Extrazine II 4L, Extrazine II DF Apply from crop emergence through 4-leaf stage of corn growth. Do not apply if 5th leaf is visible.
Broadstrike+Dual May apply to corn up to 2" in height (before the first leaf is unfurled) but before weed emergence.
Bullet May be applied after crop emergence until weeds reach the 2-leaf stage and corn is no more than 5" in height.
Dual Magnum, Dual II Magnum May be applied up to 40"-tall corn. Applications to corn in excess of 5" should be directed toward the base of the plant.
Frontier Up to 8" corn.
Guardsman, Leadoff Up to 8" corn.
Harness, Surpass, Topnotch Apply postemergence until corn reaches 11" in height.
Hornet Soil-applied rates may be used on corn up to 2" in height (before the first leaf is unfurled). Use the labeled postemergence rates for later stages.
Prowl Early postemergence--generally through 4-6-leaf. Refer to label for specific tank-mix recommendations. Culti-spray--apply from 4" through 12" corn height. Incorporate within 7 days.
Python May apply to corn up to 2" in height (before the first leaf is unfurled).

This article originally appeared on page 77 of the IC-482(11) -- May 24, 1999 issue.

Updated 05/23/1999 - 1:00pm