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Corn+Soybean Digest

Making The Most Of Corn Herbicides

Since ever-successful glyphosate hit the herbicide scene, crop protection companies have had to become more and more market savvy with the chemicals they do have.

“Many companies now simply tweak the active ingredients they already have labeled,” says Aaron Hager, a University of Illinois weed specialist. “There are no new active ingredients in 2004. If you as a manufacturer developed or discovered a new active ingredient, you're looking at $150 million to bring that to market. With today's market, it's difficult for many manufacturers to justify that sort of an investment.

“So you look at your existing inventory and ask how you're going to market what you have,” he says.

THE “NEWEST” corn herbicides are liquid formulations of proven products, products combined with other active ingredients, or chemicals licensed from one company to another. Or, in a number of cases, the newest products are combinations of glyphosate with atrazine, a different active ingredient or a different salt. Companies are attempting to control weeds no longer being consistently controlled with glyphosate alone.

“When you put 7.5 million acres — roughly 75% of the acres in the state of Illinois — under one management practice, that's a lot of acres to be putting one chemical on,” Hager says. “Eventually, Mother Nature is going to find some weed that can live in this modified environment.”

In fact, he adds, waterhemp and marestail aren't the only weeds not always consistently controlled by glyphosate — as the species once were. Lambsquarters are also breaking through in Illinois. “Maybe we have selected out most of the susceptible weeds from the fields and we're left with the populations that are more inherently tolerant to glyphosate.

“We would like to see other mode-of-action herbicides used to slow the selection for glyphosate-resistant weeds or weed species shifts,” Hager adds. “But when a farmer achieves very good control with one shot of glyphosate a year, he often poses the question, ‘Why should I do anything else if the chemical is still working?’”

THE FOLLOWING are recently released corn weed control products, most of which will be available during the 2004 planting season.

DuPont's Steadfast ATZ is a premix of Steadfast — with the active ingredients nicosulfuron and rimsulfuron — and atrazine. Available in water-dispersible granular form, it can burn down grasses and broadleaves at application and offer residual control with a rainfall within five and seven days after application.

Equip, from Bayer CropScience, is a postemergence corn herbicide that contains foramsulfuron and iodosulfuron. It's a broad-spectrum product that controls foxtails, johnsongrass and shattercane, as well as cocklebur, lambsquarters, morningglory, ragweed and velvetleaf.

Define SC, also from Bayer CropScience, is a liquid formulation of the dry Define product. Define SC is being touted by the company as the “longest-lasting oxyacetamide on the market.”

It controls tough grasses and some small-seeded broadleaf weeds and can be used with all tillage practices. Define SC can be applied preplant incorporated up to 14 days before planting and early preplant surface-applied up to 45 days before planting when used in a sequential program. Fall application is an option for growers in Iowa, Minnesota, North and South Dakota, Wisconsin and parts of Nebraska, Illinois and Ohio.

BASF's newest herbicide, Prowl H20, is a water-based formulation of pendimethalin, with less staining potential, less odor and greater storage temperature flexibility than the Prowl EC formulation. It will also offer better performance in high surface residue and increased crop safety. It contains 3.8 lbs. of pendimethalin per gallon; the Prowl EC formulation contains 3.3 lbs./gal. Prowl H20 has no incorporation interval requirement, as is the case with Prowl EC, and will be sold in limited quantities in 2004.

Agriliance introduces Confidence, an acetochlor, as a pre-emergence corn product formulated as a liquid emulsifiable concentrate. It controls many annual grasses, small-seeded broadleaf weeds and yellow nutsedge. Confidence Xtra contains 4.3 lbs. acetachlor and 1.7 lbs. atrazine.

Stalwart C is an emulsifiable concentrate of 7.8 lbs. active metolachlor per gallon with a safener. From Sipcam Agro USA, the product provides season-long pre-emergence control of most annual grasses and small-seeded broadleaf weeds. Sipcam's Stalwart Xtra contains 2.4 lbs. metolachlor and 3.1 lbs. atrazine/gal. It can be applied before or after planting in a 5.5-lb. flowable formulation.

Recoil, from Nufarm Americas, is a combination of glyphosate and 2,4-D acid. “Recoil incorporates glyphosate with an adequate concentration of 2,4-D acid, instead of commonly tankmixed esters or amines,” says Tim Birkel, NuFarm marketing specialist. “2,4-D acid eliminates volatility and provides the extra kick needed for tough broadleaf weeds showing signs of glyphosate tolerance. We're seeing quicker weed takedown and marketing it in a variety of areas for applications including in-crop Roundup Ready corn, preplant soybeans and burn down of tough perennial weeds.”

Much like Guardsman Max, BASF's G-Max Lite is a glyphosate with atrazine. It just holds a lower rate of atrazine — 1.2 lbs./acre — as compared to Guardsman Max's 1.9 lbs./acre. G-Max Lite can be applied at 2-3.5 pts./acre, depending on soil type, up to 45 days before planting. It can also be preplant-incorporated or applied pre-emergence or early post to corn up to 12 in. tall.

CoStarr, a premix of glyphosate and dicamba, is newly introduced from Albaugh, Inc. The dicamba is for residual control of broadleaf weeds such as marestail, waterhemp and wild buckwheat.

THREE NEW GLYPHOSATE formulations offer a potassium salt rather than the usual isopropylamine salt. Roundup Original Max, from Monsanto, is a potassium salt of glyphosate formulated as a 4.5-lb. acid equivalent per gallon. It is fully loaded with surfactant — just not the TranSorb II surfactant system in many of Monsanto's glyphosate products. Product use rates will range from 22 to 32 oz./acre.

Syngenta's Touchdown Total is labeled for over-the-top use in glyphosate-tolerant corn and as a pre-emerge burndown for conventional and glyphosate-tolerant crop systems. A non-selective potassium glyphosate, its popular use rate is 24 oz./acre (1.5 pints). It treats 5.3 acres/gal., allowing growers to store, handle and apply less product.

“Touchdown Total excels in knocking out difficult broadleaf weeds, including lambsquarters, foxtail, velvetleaf, waterhemp and both common and giant ragweed,” says Chuck Foresman, Syngenta technical business manager. “Over the past five years, Syngenta field trials have proved Touchdown Total is a flexible herbicide solution across a broad spectrum of weeds and in a wide range of environmental and field conditions.”

It is a 4.17-lb. acid equivalent per gallon formulation that contains the company's fully loaded IQ technology adjuvant system.

Touchdown HiTech, another potassium glyphosate, is also from Syngenta and awaiting full Environmental Protection Agency registration early in 2004. It's formulated as a 5-lb. acid equivalent per gallon and does not come with a built-in adjuvant system. It can also be used as a burndown and on Roundup Ready crops.

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