This season brings several new corn and soybean herbicides to the market. While some of these herbicides are marketed specifically for use in herbicide-resistant crops, others can also be used to reduce the risk of early-season weed competition. All but one of these herbicides contain active ingredients that have been previously marketed. The single new herbicide ingredient, tembotrione in Laudis, has a mode of action in the HPPD-inhibitor (or bleaching) family, which is not new. Therefore, these herbicides represent new tools based on existing herbicide technology. In terms of new silver bullets to solve herbicide-resistant weed threats, I don’t know of any new herbicide modes of action under development for corn and soybeans. Our recommendation is to continue to use these and existing herbicides in rotations and sequences to reduce the risk of herbicide-resistant weeds.

 

Surestart (Dow AgroSciences) is a preemergence grass and broadleaf herbicide that is specifically labeled for use with glyphosate-resistant or Liberty Link corn. Use rates are 1.5 to 2 pt/a. At 1.5 pt, SureStart contains the equivalent of 0.88 pt Surpass + 2.3 oz Stinger + 0.45 oz Python. This is slightly less than a half rate of Surpass and about a half rate of Hornet (ie Stinger + Python). Consequently, this herbicide is only intended to provide early season weed suppression prior to a postemergence application of glyphosate or Liberty. Although SureStart’s best fit is a preemergence treatment, it can be tank mixed with glyphosate or Liberty and applied postemergence to corn up to 11 inches tall. Corn should have good tolerance to SureStart because of the reduced herbicide rates within the premix. Wheat can be planted after 4 months and alfalfa, barley, oats, and soybeans can be planted the following spring. Sweet corn and potato can’t be planted for 18 months after application and peas and snap beans can’t be planted for 2 years.  (Certain sweet corn hybrids can be planted after 10.5 months – check supplemental label.)

 

Halex (Syngenta) is a postemergence grass and broadleaf herbicide labeled specifically for glyphosate-resistant corn. Use rates are 3.6 to 4 pt/a. At 3.6 pt, Halex contains the equivalent of 0.9 lb ae glyphosate + 1 pt Dual Magnum + 3 oz Callisto. In this mixture, the glyphosate should control emerged grass and broadleaf weeds well as the rate is slightly higher than typical early postemergence glyphosate rates. The Callisto component will also provide a second mode of action for postemergence broadleaf weed control plus residual activity. The reduced rate of Dual should provide desired residual grass control if activated with a rain. Although the Halex label allows applications on corn up to 30 inches tall or the V8 stage, the label wisely recommends treating weeds before they are 4 inches tall. Surfactant should be added to Halex at 0.25-0.5% plus 8.5 to 17 lb ammonium sulfate /100 gal of spray mix. Atrazine can be tank mixed with Halex at 0.25 to 0.5 lb/a, but this mixture needs to be applied before corn exceeds 12 inches tall. Field and sweet corn can be replanted anytime after application; wheat and barley can be planted after 120 days; alfalfa, potatoes, soybean, and tobacco are common crops that can be planted after 10 months; while several other crops cannot be planted for 18 months.

 

Laudis (Bayer CropScience) contains a new active ingredient called tembotrione at 3.5 lb/gal plus a safener. Tembotrione is a HPPD inhibitor, which causes bleaching, and has the same mode of action as Callisto and Impact. Laudis is a postemergence herbicide for broadleaf and grass weed control in field, seed, sweet, and popcorn. It is applied at 3 fluid oz/a and should be mixed with 1% crop oil or methylated seed oil plus 1.5 qt/a 28% UAN or 8.5 lb ammonium sulfate/100 gal of mix. Methylated seed oil is preferred over crop oil if Laudis is being used as a 1-pass postemergence program to maximize the grass control. Using Laudis in a 2-pass program where it follows a preemergence grass herbicide may be preferred and then crop oil could be used as broadleaf weeds are the primary target. In general, Laudis is a strong broadleaf herbicide and controls many common annual broadleaf weeds, but it also controls several annual grasses. Fall panicum is one grass species that will likely escape control. Laudis’ grass and broadleaf spectrum of activity is more similar to Impact, but broader than Callisto, which primarily controls broadleaf weeds. Field corn can be treated up to the V8 stage and sweet corn up to the V7 stage and most weeds should be sprayed before exceeding 6 inches tall. Laudis is synergized with 0.5 lb/a atrazine, which would be a common tank mixture. Laudis could also be mixed at 2 oz/a with Liberty or at 3 oz/a with glyphosate. With the safener in Laudis, field corn appears to have excellent tolerance to Laudis. Nearly all sweet corn hybrids also have excellent tolerance (see article in previous issue). Small grains can be planted after 4 months and alfalfa, soybean, potato, peas, and snap bean can be planted after 8 to 10 months.

 

Require Q and Resolve Q (DuPont) are two new postemergence herbicides designed to be tank mixed with glyphosate or Liberty for use on those resistant field corn hybrids. Both premix herbicides are built on the back of Resolve (rimsulfuron) and include a safener, which is denoted by the “Q”. Require Q is labeled at 4 oz/a and contains the equivalent of 1 oz/a Resolve + 3.8 oz/a Banvel. Resolve Q is labeled at 1.25 oz/a and contains the equivalent of 0.9 oz/a Resolve + 0.1 oz/a Harmony SG. The application timing of Require Q is V2-V6 stage corn or 4-20 inches tall. Because Resolve Q lacks dicamba, its application stage is wider at 0-V6 or 20 inches. If either if these herbicides is mixed with a fully loaded glyphosate, only 2 qt/a 28% UAN or 2 lb/a ammonium sulfate is needed. If the glyphosate is not loaded, 0.25% surfactant should be added along with the nitrogen source. Both of these herbicides will add a second or third mode of action to a glyphosate application, which will aid in resistance management. Limited residual grass activity is also possible with an activating rain. Rotation to most field and vegetable crops is permitted after the application of both of these herbicides.

 

Valor XLT (Valent) is a preemergence broadleaf herbicide for soybeans in southern Wisconsin (south of I-90 west of Madison and south of I-94 east of Madison). The labeled rate is 2.5 oz/a which provides the equivalent of 1.5 oz/a Valor SX + 1 oz/a Classic. The high Classic rate limits Valor XLT to southern Wisconsin where the risk of carryover is manageable. Valor XLT could be applied in the fall for dandelion control (relying primarily on the Classic component); in the spring for as part of a burndown and residual program in no-till; or as a preemergence residual program after planting. Preemergence applications need to be made within 3 days after planting to reduce the injury risk of the Valor SX component on emerging soybeans. Valor XLT will have residual activity on lambsquarters, horseweed, pigweed, velvetleaf, and common ragweed.

In burndown applications, Valor XLT can be mixed with 2,4-D or glyphosate to broaden the weed spectrum. Additional residual grass activity can be gained with Prowl tank mixtures, but Valor XLT should not be mixed with the seedling shoot growth inhibitors (ie Dual, Intrro, Outlook). Additional residual broadleaf control can be gained with Sencor or Valor SX tank mixtures. Wheat and barley can be planted 4 months after a Valor XLT application; field corn and tobacco after 10 months; alfalfa, peas, snap beans after 12 months; sweet corn after 18 months; and oats and potatoes after 30 months.

 

Authority MTZ (FMC) is a preemergence broadleaf herbicide for soybeans. Use rates are 12 to 20 oz/a, but reduced rates of 8 to 14 oz/a are labeled if Authority MTZ is followed by glyphosate. At a 12 oz rate, Authority MTZ would provide the equivalent of 4.3 fl oz Spartan + 4.3 oz Sencor. It can be applied up to 30 days before planting to 3 days after planting. This premix will provide residual control of many common weeds such as lambsquarters, pigweed, velvetleaf, and common ragweed. It will also provide some suppression of annual grasses. Authority MTZ can be mixed with any of the preemergence grass herbicides to full grass control in conventional soybeans. Wheat can be planted 4 months after an Authority MTZ application; field corn after 10 months; alfalfa, small grains, and dry beans after 12 months; and sweet corn and potatoes after 18 months.

 

Envive (DuPont) is a burndown/preemergence soybean herbicide that is similar to Valor XLT in many ways. Its use rate is 2.5 oz/a, which provides 0.9 oz/a Classic + 1.4 oz/a Valor SX + 0.14 oz/a Harmony SG. The Classic and Valor SX rates in Envive are slightly less than in Valor XLT, but it adds Harmony SG, which has more foliar activity than residual activity. Envive’s use is also limited to southern Wisconsin (south of I-90 west of Madison and south of I-94 east of Madison). Envive’s application programs are similar to Valor XLT with fall (dandelion control), spring burndown, and preemergence residual options for certain annual broadleaf weeds. Preemergence applications need to be applied within 3 days after planting. Envive is recommended for burndown of 3 inch tall weeds like mustards, common and giant ragweed, pigweed, and velvetleaf. A tank mix with 2,4-D is recommended for lambsquarters and horseweed control. Wheat and barley can be planted 4 months after an Envive application; field corn after 10 months; alfalfa, peas, and snap beans after 12 months; sweet corn after 18 months; and potatoes after 30 months.

 

Enlite (DuPont) is the northern version of Envive for all of Wisconsin as it is “light” on the Classic component. Enlite’s use rate is 2.8 oz/a, which provides 0.3 oz/a Classic + 2 oz/a Valor SX + 0.5 oz/a Harmony SG. It will provide burndown and preemergence broadleaf control in soybean with the same fall, spring burndown, and preemergence (within 3 days after planting) timings. Enlite is recommended for burndown of 3 inch tall weeds like mustards, pigweed, and lambsquarters. 2,4-D or glyphosate may be tank mixed for full spectrum control. Enlite would have residual activity on weeds like lambsquarters, horseweed, nightshade, and pigweeds.  Wheat and barley can be planted 4 months after an Enlite application; field corn, sweet corn, peas, and snap beans after 9 months; alfalfa and oats after 12 months; and potatoes after 30 months.