2005 Missouri Herbicide Update By Kevin Bradley and Andy Kendig

New herbicides and systems

Corn

Lexar is a new corn herbicide from Syngenta that contains S-metolachlor (Dual II Magnum/others), atrazine, and mesotrione (Callisto) in a prepackaged mixture. Lexar can be applied from 14 days prior to planting up to 12-inch tall corn. In fields with less than 3% organic matter, Lexar should be applied at a rate of 3 quarts per acre. In fields that have 3% organic matter or greater, Lexar should be applied at 3½ quarts per acre. The 3 quart rate of Lexar is equivalent to applying 1.3 pints of Dual II Magnum, 1.3 quarts of atrazine, and 5.3 ounces of Callisto per acre. Lexar contains the same active ingredients as Lumax but at different ratios. When comparing standard use rates of the two products, Lexar generally has less Dual II Magnum, more atrazine, and an equivalent amount of Callisto per acre. This ratio and formulation appears to be better suited for the predominant weeds and soil types encountered in Missouri compared to the ratio of these products in Lumax.

In 2004, Starane from DowAgroSciences received a label for use in corn in Missouri. Starane contains the active ingredient fluroxypyr, which is a growth-regulator type herbicide like 2,4-D and dicamba that acts only on broadleaf plants. Starane may be applied as a postemergence treatment on corn up to the V5 stage of growth. Drop nozzles are required for Starane applications made after the V5 stage of corn growth. The recommended use rate of Starane will be 2/3 pint per acre. Key weeds listed on the label include cocklebur, ragweed, kochia, sun ower, and velvetleaf. Starane may also be applied as a preplant burndown to control emerged weeds prior to corn planting. Starane may be tank mixed with atrazine, Hornet, Steadfast, and glyphosate in corn.

Generic Metolachlor Products. Recently, there have been several new generic metolachlor products introduced onto the marketplace. The Stalwart line of products from Sipcam Agro USA are some of the more popular of these products in Missouri, but Me-Too-Lachlor and Me-Too-Lachlor II are also generic metolachlor products from Drexler. Stalwart is registered for use in cotton and soybean while Stalwart C and Stalwart Xtra (metolachlor + atrazine) are registered for use in corn. Me-Too-Lachlor is registered for use in cotton and soybeans while Me-Too-Lachlor II is registered for use in corn. All of these products contain the active ingredient metolachlor, which technically is a mixture of equal parts of two isomer pairs of metolachlor, commonly referred to as the R and S isomers. This was also the case with the metolachlor within the older Dual and Dual II products from Syngenta, but is not the case with Dual Magnum and Dual II Magnum. Dual Magnum and Dual II Magnum are enriched, or resolved, with the S-isomer of metolachlor, which has been demonstrated to be more biologically active than the earlier “mixed isomer” formulations. For these reasons, generic metolachlor products such as those within the Stalwart line should not be considered “equivalent” to the same rates of Dual Magnum and Dual II Magnum. Although we normally consider generic products to be the same as the original trade name products (as with the isopropylamine salt of glyphosate), this may not be the case with the new generic metolachlors. For an excellent review of this topic, see a recent article written by Dr. Bob Hartzler at Iowa State University: http://www.weeds.iastate.edu/mgmt/2004/stalwart2.shtml. Another, perhaps less obvious, difference in these new products is the safener that is utilized to provide safety to corn. For example, Dual II Magnum, Dual Magnum, and Bicep II Magnum from Syngenta contain the safener benoxacor. The safener in Stalwart C is dichlormid. Some weed scientists have suggested that there may be differences in corn safety as a result of the different safeners in these products, which is a topic currently being investigated at several universities across the U.S.

Soybean

Canopy EX is a new prepackaged mix of Classic (chlorimuron) and Express (tribenuron) from DuPont. DuPont will no longer manufacture Canopy XL, which contained Classic and Authority (sulfentrazone). All remaining stocks of Canopy XL are expected to be sold out by early 2005. It is important to note that the new product does not contain Authority, which has been replaced with Express. The addition of Express can be considered a benefit for many, as Express is particularly effective on chickweed and many Canopy XL treatments were applied in combination with Express in fields where chickweed was present. The loss of Authority in this new product, however, may impact the level of summer annual weed suppression observed at planting. Our research has shown that Canopy XL provides excellent control of most winter annual weeds and often provides the added benefit of delaying the emergence of some summer annual weeds like common lambsquarters and common waterhemp. Although some research suggests that Canopy EX is likely to be as effective on winter annual weeds as Canopy XL, it does not appear that this new product will be as effective at delaying the emergence of some of our most common summer annual weeds like waterhemp. Sulfentrazone, one of the active ingredients in Canopy XL that is not included in Canopy EX, is especially good on waterhemp, so the effect of this new product on this weed remains to be seen. Canopy EX may be applied at rates ranging from 1.1 to 3.3 ounces per acre, with 2.2 ounces per acre being a standard use rate for Missouri. Unlike Canopy XL, Canopy EX can only be applied up to 45 days prior to soybean planting.

Generic Metolachlor Products. See information pertaining to these products above in the corn section.

Sulfentrazone. All remaining stocks of Authority 75DF from DuPont are expected to be sold out by the 2005 growing season. The active ingredient in Authority, sulfentrazone, is owned and manufactured by FMC. FMC has moved their production plants for sulfentrazone, which may tighten supplies of this active ingredient in 2005. In 2005, FMC expects to have Spartan 4F available and should have full capacity supplies of this product available by 2006. It appears that Tenkoz will still have supplies of their product, Blanket 75DF, available in 2004 and 2005.

Wheat

Olympus is a new ALS-inhibiting herbicide from Bayer CropScience for use in wheat. The active ingredient in Olympus is propoxycarbazone-sodium. Olympus can be applied to winter wheat from emergence up to jointing at rates ranging from 0.6 to 0.9 ounce per acre. A nonionic surfactant is required with all Olympus applications. Olympus is particularly effective on Bromus species, including Japanese brome, soft chess, ripgut brome, cheat, and downy brome, which is the species that seems to dominate in Missouri. Olympus is also registered for the control of some winter annual broadleaf weeds like shepherd’s-purse, field pennycress, and certain mustards. Although Olympus will provide good control of some grasses that are especially troublesome for some wheat growers in Missouri, the crop rotational restrictions may limit the use of this product for growers who wish to double-crop soybeans following wheat or rotate to corn in the following season. For example, corn may not be planted for 18 months after an Olympus application and conventional or RR soybeans may not be planted for 12 months after an Olympus application. STS soybeans, however, may be planted 4 months after an Olympus application, which would allow a wheat grower to make a fall Olympus application and plant double-crop STS soybeans after wheat harvest. Bayer is working to resolve the issue of crop rotational flexibility by developing a new product called Olympus Flex, which may be available to growers in the future.

Osprey. Osprey is another new ALS-inhibiting herbicide from Bayer CropScience for use on wheat from the 1-leaf to 2-tiller stage at 4.75 ounces per acre. The active ingredient in Osprey is mesosulfuron. Osprey provides excellent control of Italian or annual ryegrass, which appears to be a problem for some producers in the southern portion of Missouri, but is not yet a widespread statewide problem in wheat as it is in many other areas. As Osprey is an ALS-inhibiting herbicide, it is particularly effective in controlling Hoelon-resistant Italian ryegrass populations that have developed in many areas. Osprey also provides some suppression of Bromus species like downy brome and cheat, but generally less control than what is considered “commercially acceptable.” Soybeans may be planted 3 months after an Osprey application while the rotational interval for corn following an Osprey application is 12 months.

Grass pastures and hay

Surmount is a new prepackaged herbicide mixture from Dow AgroSciences for use in permanent grass pastures, rangeland, fencerows, nonirrigation ditch banks, and around farm buildings. Surmount contains 0.67 lb of picloram and 0.67 lb of fluroxypyr per gallon of product. Picloram is the active ingredient in Tordon and also one of the active ingredients in Grazon P+D while fluroxypyr is sold as Starane and registered for use in corn and grain sorghum. Both of these active ingredients are growth regulator-type herbicides that act on broadleaf plants only and are safe to established grasses. Key weeds listed on the Surmount label include horsenettle, ironweed, thistles, and blackberry. Surmount will be recommended primarily for brush control at rates ranging from 3 to 5 pints per acre or as a high volume foliar treatment at 1 to 1½ % v/v. Surmount can also be applied for herbaceous weed control at 1½ to 2 pints per acre. For nonlactating dairy animals and all other livestock, there are no grazing restrictions and a 7-day haying restriction following an application of Surmount. For lactating dairy animals there is a 14-day grazing and haying restriction following an application of Surmount.

PastureGard is also a new prepackaged herbicide mixture from Dow AgroSciences for use in permanent grass pastures, rangeland, fencerows, nonirrigation ditch banks, and around farm buildings. PastureGard contains 1.5 lb of triclopyr and ½ lb of fluroxypyr per gallon of product. Triclopyr is an active ingredient in Remedy and Garlon and is also one of the active ingredients in Crossbow while fluroxypyr is sold as Starane. Both of these active ingredients are growth-regulator type herbicides that act on broadleaf plants only and are safe to established grasses. PastureGard is targeted primarily as a brush control product and may be applied as a broadcast treatment or on individual plants as a foliar, basal bark, or cut-stump treatment. Key weeds listed on the label include blackberry, multiflora rose, Sericea lespedeza, Osage orange, and many other woody or brush species. PastureGard can be applied for herbaceous weed control at rates ranging from 1½ to 3 pints per acre, as a broadcast treatment for brush species at 3 to 6 pints per acre, as a high volume foliar individual plant treatment at 1 to 1½ % v/v, and as a low volume basal treatment at a 1:1 ratio of PastureGard : Oil. For nonlactating dairy animals and all other livestock, there are no grazing restrictions and a 14-day haying restriction following an application of PastureGard. For lactating dairy animals, treated pastures should not be grazed or hay should not be removed from these areas until the next growing season.

It appears that Aim will receive a new label that will include a variety of crops that are not currently listed on the label. It appears that this new label will allow the use of Aim on pastures or grass for seed production. As this label is pending for Missouri, the specifics of this label should be confirmed before applying Aim to any of these areas in 2005.

Journey is a new prepackaged mix of imazapic and glyphosate from BASF. Imazapic was the active ingredient in Plateau, which will no longer be available for sale over-the-counter to pasture and forage producers. Journey is registered for use on a number of industrial sites, on conservation reserve program (CRP) areas, on established coastal bermudagrass, and prior to the establishment of certain native prairie grasses. However, it is important for pasture and forage producers to realize that this product is not to be used on any grass that will be grazed or used for hay.

Plateau will no longer be for sale directly to growers over-the-counter but may possibly be obtained through state and federal regulatory offices such as the natural resources conservation service (NRCS). The active ingredient in Plateau is imazapic, and was one of the few herbicides that could be used in warm- and cool-season grass pastures, including sprigged and established bermudagrass, for the control of other weedy grasses like large crabgrass and giant foxtail.

Cotton

Generic Metolachlor Products. See information pertaining to these products above in the corn section.

Grain sorghum

In 2004, Starane from DowAgroSciences received a label for use in grain sorghum in Missouri. Starane contains the active ingredient fluroxypyr, which is a growth-regulator type herbicide like 2, 4-D and dicamba that acts on broadleaf plants only. Starane may be applied as a postemergence treatment on grain sorghum from the 3- to the 7-leaf stage of grain sorghum. Drop nozzles are required for Starane applications made to grain sorghum that is in the 8-leaf to the boot stage of growth. The recommended use rate of Starane will be 2/3 pint per acre. Key weeds listed on the label include cocklebur, ragweed, kochia, sunflower, and velvetleaf. Starane may also be applied as a preplant burndown to control emerged weeds after planting but prior to grain sorghum emergence.

Rice

Grasp is a new herbicide for use in rice. Grasp contains penoxsulam which primarily controls broadleaf weeds and also has good activity on barnyardgrass but limited activity on secondary grasses. It is formulated as a 2 lb/gal liquid and is used at rate of 2 fluid ounces per acre (0.031 lb ai/A).

Burndown/Fallow/RR Crops

Glyphomax XRT and Durango are new glyphosate products from Dow AgroSciences that will be available in the 2005 growing season. Both Glyphomax XRT and Durango contain the isopropylamine salt of glyphosate and are identical products. The Glyphomax XRT will be marketed as the “service” brand while Durango will be marketed as the “no service” brand. Both products are formulated as a 4 lb acid equivalent per gallon (5.4 lb active ingredient per gallon) and are fully loaded with a surfactant. The standard use rate for these products is 24 fluid ounces per acre (1½ pints per acre), which is equivalent to the 32 fluid ounce rate of other products like Glyphomax Plus, Roundup Original, etc.

Label updates

Corn

It appears that Aim will receive a new label that will include a variety of new crops as well as several updates to crops that are currently included on the label. In corn, the Aim label will be modified for use past the 8-collar growth stage.

Atrazine Re-registration in the United States. The Environmental Protection Agency (EPA) recently completed a 10-year review of the health and environmental effects of atrazine. Upon completion of this review, the EPA issued a favorable re-registration decision for atrazine, indicating that farmers will be able to continue using this active ingredient in corn, grain sorghum, and on other labeled crops. As part of this review process, ALL atrazine-containing product labels must be changed to reflect minor changes that have been made with respect to watershed monitoring programs, usage, and handling of atrazine. The list of products is too extensive to be covered here but covers approximately 140 different atrazine-containing products manufactured and sold by several different chemical companies. Products currently in inventory must also be re-stickered with new supplemental labels that reflect the changes discussed above. These changes will not affect the current maximum use rates for atrazine in Missouri.

Lumax. The label for Lumax will be amended to indicate that postemergence applications of this product can be made on corn from preplant up to 12 inches in height. Previously, this product could only be applied to corn that was 5 inches in height.

Soybean

It appears that Aim will receive a new label that will include a variety of new crops as well as several updates for crops that are currently included on the label. In soybean, the Aim label will be modified for use up to the 6th trifoliate rather than the 3rd trifoliate restriction as the label currently stands. Additionally, it appears that Aim will receive a harvest aid label for the burndown of large weeds like pigweed that may be remaining at harvest.

Backdraft, a prepackaged herbicide mixture from BASF that contains the active ingredients imazaquin and glyphosate, will be discontinued in 2005.

Pursuit DG and Pursuit 2AS. BASF will no longer formulate imazethapyr in a dispersible granule formulation (Pursuit DG) but will continue to market the liquid formulation of imazethapyr, sold under the trade name Pursuit 2AS. The remaining inventory of Pursuit DG is being used up but by 2005 the vast majority of imazethapyr available on the market will be sold as the liquid formulation of Pursuit. The use rate will be an important thing to consider (and not confuse) during the transition period as the standard use rate of Pursuit DG was 1.44 ounces per acre while the standard use rate of Pursuit EC is 4 fluid ounces per acre.

Scepter will no longer be sold in Eco-Pacs but will be sold in 28-ounce bottles.

Sequence is a prepackaged mix from Syngenta that contains 2.25 lb of the potassium salt of glyphosate on an acid equivalent basis plus 3 lb of metolachlor per gallon of product. Sequence is now registered for preemergence applications on non-Roundup Ready soybean and also for applications on Roundup Ready soybean from cracking up to the V3 (3rd trifoliate) stage of soybean growth. Sequence will primarily be used at rates ranging from 2½ to 3 pints per acre. The 2½ pint rate of Sequence is equivalent to applying 0.7 pounds of the potassium salt of glyphosate plus 1 pint of Dual II Magnum per acre while the 3 pint rate is equivalent to applying 0.8 pounds of the potassium salt of glyphosate plus 1.2 pints of Dual II Magnum per acre. As a result of the active ingredients included in this prepackaged herbicide mixture, Sequence should provide control of most annual weeds that are emerged at the time of application and also provide residual control of certain grass and small-seeded broadleaf weeds that might typically germinate after the initial herbicide application.

Steadfast received a few label changes in the spring of 2004. These include allowing the use of methylated seed oils at 0.5% v/v, allowing tank-mix combinations with Callisto at 1½ to 3 fluid ounces per acre, and allowing tank-mix combinations of Lumax at 2 pints per acre on corn no more than 5 inches in height.

Synchrony STS has received a new 2ee label in Kansas and Missouri that allows for fall burndowns of this product with Express. It is important to remember that Express requires a 45-day preplant interval for soybeans.

Kevin Bradley, Agronomy
(573) 882-4039

Andy Kendig, Agronomy,
Delta Research Center
(573) 379-4031