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ExpressSun™ Hits the Fields

Sunday, April 15, 2007
filed under: Weeds

EPA this spring approved labeling for the use of Express® herbicide (with TotalSolTM soluble granules) on sunflower, and DuPont, the maker of Express, is now submitting the product for state registration and approval of the new labeling.

The registration of Express on sunflower has been a partnership between DuPont and the National Sunflower Association, state universities in all the sunflower producing states, USDA IR-4 (Interregional Research Project No.4 – a federal program that helps conduct research on minor use pesticides) and the N.D. Minor Use Fund, which financed the residue trials, a registration requirement.

It’s estimated that Pioneer and Seeds 2000 will have enough seed available for about 50,000 acres in the Dakotas and Minnesota this year, with wider availability in 2008, and Canada perhaps in 2009. This year’s harvested ExpressSun NuSun acreage will be processed exclusively at ADM in Enderlin.

The ExpressSun trait in ExpressSun NuSun hybrids gives built-in tolerance to tribenuron methyl, the active ingredient in Express herbicide. Herbicide-tolerant sunflowers with the ExpressSun trait were derived through traditional plant breeding methods and are non-GMO products. Application of Express to conventional (non-Express tolerant) sunflower will result in significant crop injury or plant death.

Express herbicide is a member of the sulfonylurea family of herbicides. Research trials have demonstrated control of Canada thistle and many other annual broadleaf weeds in conventional, minimum-till or no-till sunflower production systems with the technology.

The product is applied postemergence, ¼ to ½ oz/ac, with a maximum 1 oz/ac per use season. Use concentrated crop oil or modified seed oils as an adjuvant – 2 qts/100 gal volume. Minimum spray volume of 5 gal by ground or 2 gal by air provided good weed control. Cost is estimated to be about $3.75 to $7.50 at the ¼ to ½ oz/ac use rate.

Treat ExpressSun trait sunflower from early postemergence/V1 stage to before the bud formation stage. Apply to weeds after emergence and before 4 inches in height. Note that Express herbicide (with TotalSol soluble granules) has little to no soil activity. Weeds are not controlled when emerged after application of the product.

Research has indicated good weed control with Spartan 75 WG applied at 3 to 4 oz/ac as a post-plant pre-emergence application, followed by ½ ounce Express herbicide (with TotalSol soluble granules) plus 2 qts MSO per 100 gallons of spray volume applied early post-emergence but before weeds exceed 4 inches in height. For additional grass control, DuPont Assure® II herbicide can be applied at required rates as a separate application to control target grasses.

Since domestic sunflower can readily outcross to wild sunflower, producers will need to follow specific management practices designed to preserve the efficacy of the ExpressSun trait. These practices span crops and other chemistries as well to promote herbicide resistance management.

• Always grow sunflower hybrids with the ExpressSun trait as part of a multiyear rotation with other crops.

• Use non-ALS/AHAS (non-group 2) mode of action herbicides in a tank mix with ALS/AHAS herbicides, or as sequential treatments in the rotational crop, to control wild and volunteer sunflowers.

• Control wild sunflowers in noncrop areas adjacent to ExpressSun trait sunflower fields through the use of non- ALS/AHAS herbicides and/or mowing prior to seed set.

• Use tillage to control emerged wild sunflowers prior to planting hybrids with the ExpressSun trait, or by utilizing non-ALS/AHAS burndown herbicides, or use ALS/AHAS burndown herbicides in a tank mix with non-ALS/AHAS herbicides to provide control of sunflowers.

• As practical, use ALS/AHAS herbicides in a tank mix with non-ALS/AHAS (non-group 2) mode of action herbicides or use ALS/AHAS herbicides in a sequential program that employs alternate modes of action to control wild and volunteer sunflowers.

Grower observations in this first growing season with ExpressSun hybrids and

Express herbicide will be featured in The Sunflower this winter. – Tracy Sayler

Condensed List of Broadleaf Weeds Controlled or Suppressed by Express® herbicide (with TotalSolTM soluble granules) on ExpressSun™ sunflower

Buckwheat, wild*

Chamomile, mayweed

Chickweed, common

Falseflax, smallseed



Lambsquarters: common, slimleaf

Lettuce, miner’s

Lettuce, prickly**

Mustards: black, blue(purple mustard), wild

Nightshade, hairy* Pennycress, field


Pigweed, redroot

Purslane, common


Smartweed, Pennsylvania*

Sowthistle, annual*


Thistle: Canada, Russian**

Vetch*: common, hairy

Wallflower, bushy (treacle mustard)

* Partially controlled weeds exhibit a visual reduction in numbers as well as a significant loss of vigor.

** Resistant biotypes were not always adequately controlled

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