WITH A COUPLE OF EXCEPTIONS, the focus of new corn and soybean herbicides for 2004 is convenience, competitive pricing and new marketing programs, not new chemistry.

This follows the trend of recent years in which most new herbicides have resulted from tinkering with formulations, tankmix partners and premix ingredient ratios. Of course, research and development of new chemistry continues. But with high development costs and a market already saturated with relatively effective herbicides, new chemistries continue to be the exception.

Corn growers are likely to have four new or reformulated herbicides in 2004, two of which introduce new active ingredients. A change in Roundup Ready (RR) corn germplasm allowing higher glyphosate rates and a wider application window also will change weed-control options (see sidebar).

Soybean growers will have three new or reformulated herbicide brands, but no new chemistry.

“For the most part, there's nothing new or tremendously different for 2004,” says Bob Hartzler, Iowa State University extension agronomist.

The new chemistries expected in corn — both for postemergence application — are Equip herbicide from Bayer CropScience and Starane herbicide from Dow AgroSciences.

Equip herbicide received EPA registration in April 2003, so some growers had a chance to try it last year. But 2004 will be its first season with full availability. Geared primarily for the central and southern Corn Belt, it contains two active ingredients: a new broadleaf chemistry and the active ingredient in Option herbicide for grass control.

Starane herbicide has been labeled for broadleaf weed control in small grains for several years, but its active ingredient hasn't been labeled for corn. Assuming registration is approved for corn in time for the 2004 season, it is expected to be used primarily in the western Corn Belt to control kochia. However, it has activity on several other large-seeded broadleaf weeds.

The two other new corn herbicides — Define SC and Prowl H2O — are reformulations. “The new formulations should not change weed-control performance,” Hartzler says. “The major implication is for handling.”

The new soybean herbicides are Arrow, for postemergence grass control, Intrro, for preemergence control of grasses and small-seeded broadleaves, and Touchdown Total, a new higher-load glyphosate.

Arrow, from Makteshim Agan North America (MANA), contains clethodim, the same active ingredient that is in Select and Prism herbicides. Though it controls a range of annual and perennial grasses, it will be marketed primarily for control of volunteer RR corn in RR soybeans.

The active ingredient in Intrro, from Monsanto, is alachlor. Growers who have used Lasso will know exactly what to expect, because the active ingredient in Intrro is the same as the one in Lasso.

Touchdown Total from Syngenta is 39% more concentrated than Touchdown IQ, so the recommended use rate will be 24 oz./acre instead of 32. It also has a 30-minute rainfast interval instead of one to two hours.

All three new soybean herbicides should perform the same as other herbicides containing the same active ingredients, Hartzler says.

Here are details on the new corn and soybean herbicides for 2004.

Corn herbicides

Touchdown Total boosts glyphosate concentration

New Touchdown Total from Syngenta is 39% more concentrated than most glyphosate herbicides, so growers will be able to treat more acres per gallon of herbicide.

The new formulation, which received EPA registration in November 2003, also has a 30-minute rainfast interval, down from one to two hours with Touchdown IQ, which remains on the market, says Chuck Foresman of Syngenta.

Touchdown Total contains 4.17 lbs./gal. of glyphosate acid, plus Syngenta's IQ surfactant package. It will be labeled for the same full complement of crops and uses as Touchdown IQ. The potassium-based formulation has a typical use rate of 24 oz./acre. The typical use rate of Touchdown IQ, which contains 3 lbs./gal. of glyphosate acid, is 32 oz./acre.

The other potassium-based formulation on the market, Monsanto's Roundup WeatherMax, has a recommended use rate of 22 oz./acre. The differing use rates are due to the different glyphosate acid concentrations and surfactant packages of the two products, Foresman says.

Touchdown Total will be the first glyphosate product to advise growers on ways to reduce the potential for glyphosate-resistant weeds, Foresman claims. “The cornerstone is to rotate herbicides,” he says. “We will recommend no more than two glyphosate applications over a two-year period in a corn/soybean rotation.”

In practice, that will suggest use of non-glyphosate herbicides in one or both crops. This will reduce glyphosate-resistant-weed selection pressure by introducing herbicides with other modes of action, he adds.

BASF adds no-stain, no-odor Prowl H2O

With new Prowl H2O, you can forget the strong DNA herbicide odor, the intense yellow color and the propensity to stain. There's no longer an incorporation requirement, either. But weed control will be equal and, in some cases, better than before, according to Aaron Bice of BASF.

Prowl's new saltwater-based formulation is responsible for the low odor, reduced staining and lack of incorporation requirement. The active ingredient, pendamethalin, which is unchanged, is now encapsulated in a polymer shell using a patented BASF technology. This allows it to be suspended in water, even though it normally requires a petroleum-based solvent.

The change in the incorporation requirement reflects the reduced volatility of the new formulation compared with that of the old. This doesn't mean incorporation isn't needed when rainfall isn't adequate to move the active ingredient into the soil, Bice says. But growers will have more flexibility to wait for rainfall.

The new formulation will be especially beneficial when applied on fields with heavy crop residue, because it doesn't bind to the residue, Bice explains. This allows it to be washed from the residue and into the soil profile.

Prowl H2O, which will be available in limited quantities in 2004, is registered on the same 18 crops as is the original Prowl, including corn and soybeans. At 3.8 lbs./gal. of active ingredient, it carries a heavier load than the original 3.3 lbs./gal. emulsifiable concentrate. The normal recommended use rate is 2.5 pts./acre.

Define herbicide gets new liquid formulation

Bayer CropScience introduced Define, a grass and small-seeded broadleaf corn herbicide, in 2001 as a dry flowable formulation. In 2004 it will be reborn as a liquid, pending EPA registration.

New Define SC (suspension concentrate) will open new markets among large-acreage growers and custom applicators, who tend to prefer liquids to dry formulations, says Rob Schrick of Bayer CropScience.

The new formulation, which replaces the dry version, will aid Bayer in bundling it with its other herbicides, including Balance Pro, which also is an SC, as well as in mixes with atrazine.

A typical use rate for Define SC is 1 pt./acre. Assuming it receives EPA registration, it will be available in 220-gal. shuttles and in bulk.

Equip offers one-pass grass and broadleaf control

Equip herbicide from Bayer CropScience received EPA registration in April 2003 for use on field corn. Because of the late registration, 2004 will be the first chance many growers will have to consider Equip in their weed-control programs.

Designed for postemergence control of both grass and broadleaf weeds, Equip is a premix of foramsulfuron, the active ingredient in Bayer's Option grass herbicide, and iodosulfuron, which adds control of major small- and large-seeded broadleaf weeds. It also contains a safener, which increases crop tolerance to the active ingredients. The safener also boosts crop tolerance with common tankmix partners, such as dicamba, according to Greg Perrigo of Bayer CropScience.

The herbicide's label lists a who's who of annual and perennial grasses and broadleaf weeds, including shattercane, quackgrass and dandelion. It controls weeds primarily through translocation to growing points in plant roots and shoots. However, it also offers up to two weeks of soil residual control of small-seeded broadleaf weeds, Perrigo says.

He expects Equip to best fit environmental conditions and cropping practices in the central and southern Corn Belt. Most growers are expected to apply Equip primarily as part of a sequential program following a preemergence herbicide application. But growers in the eastern and western Corn Belt may test it as a one-pass program, Perrigo adds.

Equip will not be marketed in northern areas because of rotational concerns to sensitive crops. The rotational interval to all corn types is 15 days; soybeans, cotton and oats, 9 months; winter wheat and barley, 2 months; spring wheat and barley, 8 months; and 18 months on alfalfa, sugar beets, sunflowers, potatoes, dry beans and peas.

As with many sulfonylurea (SU) herbicides, corn injury may occur if Equip is applied to corn that has been previously treated with an organophosphate (OP) insecticide. It has no use precautions with Aztec, Capture, Force and Regent and is compatible with T-band application of Counter 20CR. It should not be used in fields treated with Dyfonate, Thimet, Counter 15G or Counter 20CR in-furrow.

Equip can be broadcast over corn from the V1 through the V4 growth stage. Drop nozzles set to minimize spray contact to the corn whorl must be used from the V4 up to the V8 growth stage. The recommended use rate is 1.5 oz./acre. A water dispersible granule, it should be applied with methylated or ethylated seed coil, in combination with nitrogen fertilizer.

Starane keys on kochia, other tough broadleaves

Starane, a postemergence small grains herbicide from Dow AgroSciences with a reputation for controlling kochia when other herbicides fail, is expected to be available in 2004 for use in field corn, sweet corn and grain sorghum, pending EPA registration.

The herbicide also is labeled on other large-seeded broadleaf weeds, including cocklebur, field bindweed, hemp dogbane, ragweed, velvetleaf and wild sunflower — all up to 8 in. tall. However, it does not control important small-seeded broadleaf weeds, such as lambsquarters and pigweed.

Starane's kochia capabilities are especially important because of the preponderance of ALS-resistant kochia in the western Corn Belt. It can be applied as a burndown or an in-crop application.

The active ingredient in Starane, which has no soil residual, is fluroxypyr, a growth regulator in the same family as the active ingredients in Stinger and Hornet herbicides.

Based on previously issued Section 18 labels, Starane can be applied to field corn up to the V5 stage. In sweet corn, it's okay up to V4. On milo, it can be applied from the three- through seven-leaf stage. The recommended use rate is ⅔ pt./acre. The maximum use rate in a single growing season is 1⅓ pts./acre.

Soybean herbicides

Arrow herbicide targeted at RR volunteer corn

The new postemergence grass herbicide Arrow 2EC, from MANA, will be marketed primarily to control volunteer RR corn in RR soybeans. It contains clethodim, the same active ingredient that is in Select and Prism herbicides from Valent, whose patent recently expired.

Few growers are likely to be familiar with MANA, which is based in Israel. But many have used ag chemicals made by the company, which is the world's largest manufacturer of generic active ingredients.

Although Arrow's active ingredient controls a broad range of annual and perennial grasses, the company is keying on volunteer RR corn because of its growing importance in crop rotations, especially in the northern Corn Belt.

“This is one of the most economically important issues for growers in the Upper Midwest who grow both Roundup Ready soybeans and corn,” John Frieden of MANA says. “We believe the market for controlling volunteer Roundup Ready corn will grow precipitously over the next few years, and we want to be part of it.”

Arrow is an emulsifiable concentrate. The recommended use rate to control a broad range of grasses is 4 oz./acre.

New alachlor brand designed for RR beans

Although Intrro herbicide from Monsanto is a new brand, the active ingredient — alachlor — has been on the market for 30 years, sold primarily under the Lasso banner.

Intrro is labeled for preemergence control of grasses and small-seeded broadleaf weeds in soybeans and grain sorghum, but not corn, according to Brad Wagner of Monsanto. Lasso is still on the market and is labeled on all three crops. But the Lasso brand will be retired once supplies are gone.

By adding the new brand and eliminating corn from the label, the company avoided the possibility of the application of alachlor to additional corn acres. That is important to Monsanto, because it agreed to reductions in overall alachlor use as a condition for EPA's approval of acetochlor. That is the active ingredient in Monsanto's Harness and Degree herbicide brands and Dow AgroSciences' Surpass, FulTime and Keystone herbicides.

Since the introduction of RR soybeans, Monsanto has discouraged use of soil residual herbicides on them. However, Wagner says that Monsanto decided to market Intrro to meet the demand of the small — and stable — percentage of RR soybean growers who prefer using a residual herbicide.

Growers who use Intrro will be able to qualify for the Roundup Rewards program, assuming they meet other qualifications. Growers who apply other residual herbicides on RR soybeans are excluded from the program. Retailers are expected to price Intrro to be competitive with major soybean residual herbicides, such as Prowl, Canopy XL and Treflan.

Intrro will assist growers in controlling tough broadleaf weeds, such as tall waterhemp and black nightshade, and major annual grasses and small-seeded broadleaf weeds, Wagner says. The recommended use rate is 1.5 to 2.5 qts./acre. It is an emulsifiable concentrate with a 45% active ingredient load factor. It will be available in bulk, as well as 2.5-gal. jugs.

Herbicide label changes

Option herbicide from Bayer CropScience can be applied from the V1 through V6 corn growth stages, slightly longer than in the past. Callisto herbicide will be added as a tankmix partner.

Syngenta is anticipating label changes for Lumax and Camix herbicides to allow application on yellow popcorn.

Labels for Monsanto Roundup WeatherMax and Roundup UltraMax herbicides have been changed to allow higher use rates and a wider application window on Roundup Ready Corn 2 hybrids.

Gangster herbicide from Valent will have a unified label in 2004. The multipack herbicide has had separate labels for its two active ingredients.

New Roundup Ready corn boosts rates, widens application window

Beginning in 2004, many Roundup Ready (RR) corn hybrids will allow growers to use higher glyphosate herbicide rates over a longer period than in the past.

Depending on the seed company, the new RR corn hybrids have different names. Monsanto, Asgrow, Dekalb and most other seed companies with the technology are using the name Roundup Ready Corn 2. Pioneer Hi-Bred International will market the hybrids as Roundup Ready, but without the “2” designation. All Pioneer corn hybrids with RR technology contain the gene that allows the higher use rates and wider application window.

Higher rates, higher total

The new RR corn hybrids allow labeled glyphosate products to be applied at higher single-application rates and allow a higher total amount during the growing season. For example, Roundup WeatherMax can be applied at rates up to 32 oz./acre in a single application and up to 64 oz./acre during the growing season. In the past, WeatherMax was limited to 22 oz./acre in a single application and 44 oz./acre during the season.

Both Roundup WeatherMax and Roundup UltraMax have received new labels allowing the higher rates and a wider application window. Other glyphosate herbicides must be relabeled to allow the new use.

The new wider application window will allow over-the-top glyphosate applications through the V8 corn growth stage, about 30 in. tall, as allowed in the past. Glyphosate also will be able to be applied with drop nozzles until corn is 48 in. tall, which has not been allowed. Asgrow, Dekalb and many other seed companies use the term “SprayFlex Protection” to describe the changes.

Additional tolerance required

The reason for the higher rates and wider window is a shift in which RR “event” is used to confer tolerance to glyphosate in corn hybrids. When RR corn was introduced, tolerance was conferred by the GA21 event. Now the industry is switching to the NK603 event because it confers the additional tolerance required for the higher herbicide rates and the wider application window, says Rick Cole of Monsanto.

Until the GA21 event is completely phased out over the next two to three years, growers should be aware of which RR corn technology they are planting, Cole says.

However, at normal glyphosate use rates for labeled weeds, RR corn hybrids can be managed the same.

“Our recommended use rate of 16 to 22 oz./acre hasn't changed, nor has our recommendation to spray weeds early,” Cole says. “At those rates, crop safety is excellent for both events. There is no safety difference for one event versus another at normal use rates.”

Cole expects the higher use rates allowed on Roundup Ready Corn 2 hybrids to come into play on larger tough-to-control weeds, such as black nightshade, velvetleaf and annual morningglory. For example, at the 22 oz./acre use rate, WeatherMax is labeled for velvetleaf and black nightshade up to 6 in. tall. At the 32-oz./acre Roundup Ready Corn 2 rate, the weed size limit is 12 in.

“We recommend spraying weeds when they are small,” Cole says. “But when growers can't get into the field early, this change provides a solution that is highly effective.”