NDSU Crop and Pest Report

ISSUE 1  May 1, 2003



Dual Magnum has recently received EPA registration for use on sugarbeet. Dual Magnum can be fall applied or used in the spring preplant incorporated prior to seeding, preemergence after seeding or as a lay-by treatment. Optimum Dual Magnum rates vary with soil organic matter content and application timing so the label should be consulted for rate selection. Lay-by treatments of Dual Magnum alone may be applied as soon as the sugarbeet reach the two-true-leaf stage. Lay-by Dual Magnum in combination with other herbicides should be applied after the sugarbeet has four true leaves to reduce the risk of sugarbeet injury.

Preplant incorporated Dual Magnum has provided more consistent weed control than preemergence Dual Magnum since rainfall necessary to activate preemergence Dual Magnum may not occur for several days. Dual Magnum is degraded by sunlight and half of the applied active ingredient can disappear if the herbicide lays on the soil surface for 8 to 10 days without rain or incorporation. Dual Magnum will provide weed control for 6 to 8 weeks after application.

Incorporation of Dual Magnum does not need to be deep but good uniformity of incorporation is important. The incorporating tool can be run through a strip of lime or flour to evaluate uniformity of distribution in the soil. Incorporation methods that leave streaks should be avoided. Two passes with the incorporating tool may be needed to achieve uniform distribution.

Dual Magnum may cause occasional injury to sugarbeet. In past experiments in North Dakota and Minnesota, 0 to 17% injury was observed at eight of nine locations which is not a worrysome level of injury. However, injury was 26% at the ninth location and this level of injury was a concern. Seeding rates may be increased as a hedge against stand loss from Dual Magnum. Injury would be expected to be increased with slow emergence in wet cool soils and on soils with less clay and organic matter. Stunting of sugarbeet from Dual Magnum would not be expected to cause yield loss but stand loss from Dual Magnum may cause yield loss if the remaining sugarbeet population is insufficient for optimum yield or if the population has gaps that allow late weed establishment.

Dual Magnum is rated to provide good to excellent control of pigweed species, green foxtail and yellow foxtail. Dual Magnum is rated as fair on wild oats, common lambsquarters, Russian thistle and common ragweed.

Alan Dexter
NDSU/U of MN Extension Sugarbeet Weed Specialist



All herbicides Section 18 emergency registrations that have been granted in North Dakota have been posted on the web and are up to date as of 5/1/2003.

All 24c and 2ee herbicide registrations granted in North Dakota since 1999 have been posted on the web and are up to date as of 5/1/2003.

The URL is:


Summary of 2002 herbicide Section 18s approved for ND:

New Full Section 3 Federal Registrations:

New Section 24c Registrations:

New 2ee labels:

New Supplemental herbicide labels:

Richard Zollinger
NDSU Extension Weed Specialist


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