What’s New for Agronomic Weed Control
Posted: March 2, 2017
Acuron Flexi 3.26SC (bicyclopyrone + mesotrione [Callisto] + s-metolachlor [Dual II Magnum] + benoxacor [corn safener]; groups 27 and 15 herbicides; Syngenta) is similar to Acuron but does not contain atrazine. It controls many annual grasses, broadleaves, and nutsedge. It is labeled on all corn types including sweet corn. It can be applied pre or post up to 30” tall corn; 3” tall annual broadleaf weeds but is inconsistent on emerged grasses. Typical use rate for Acuron Flexi will be 2 qt/A. It will be available for the 2017 growing season.
Armezon PRO 5.35SE (topramezone + dimethenamid-P [Outlook]; groups 27 and 15; BASF) is registered for use in corn (field and sweet) for post applications. The Armezon component provides foliar control of certain annual grasses and broadleaves, while Outlook gives residual control of many annual weeds that may germinate after application. The typical use rate is16-20 oz.
DiFlexx DUO 1.53SC (dicamba + tembotrione (Laudis) + corn safener; group 4 and 27; Bayer CropScience) can be used in field corn for control of broadleaves and annual grasses. Typical use rate is 24 – 40 fl oz/A. For best results apply before annual broadleaf weeds reach 6” tall and grasses, 3” tall. It can be tank-mixed with other corn herbicides to broaden the weed control spectrum. DiFlexx Duo at 32 fl oz/A equals 10.25 oz DiFlexx + 2.5 oz Laudis. It can be applied from corn emergence to 36 inches tall (<V7 stage) and drop nozzles can be used thereafter. Always include spray additives such as liquid nitrogen solution or ammonium sulfate plus methylated seed oil or crop oil concentrate to improve control.
Halauxifen-methyl dubbed “Arylex Active” (Dow AgroSciences) is a new plant growth regulator herbicide (group 4) similar to 2,4-D and dicamba but is not a new mode of action.
It is active at very low use rates, rapidly degrades in soil, and has no soil activity or residual control. Halauxifen controls only broadleaf weeds such as marestail, deadnettle, pigweed, lambsquarters, and is rather weak on common chickweed. Penn State has not yet evaluated this product for weed control but reports from other universities claim it has better activity on marestail than 2,4-D but similar to dicamba. Halauxifen containing products initially will include:
- Elevore SC (halauxifen only) will be labeled in corn, small grains, pastures, turf; and for burndown in soybean. The initial label will allow a 14 day early preplant in soybean and corn but this will likely be reduced at some point. The use rate ranges from 1-2 oz/A and may be tank mixed with glyphosate and other labeled herbicides to broaden the control spectrum. Elevore will likely be available in 2017.
- Quelex 20.4WDG (halaxifen and florasulam (group 2)) is currently, labeled in wheat, barley, and triticale. The use rate of 0.75 oz/A controls many common broadleaf weeds in cereals when applied to 2-4” tall weeds. It can be tank-mixed with other herbicides to improve the weed spectrum. Always include necessary adjuvants for effective control and keep in mind it can be used in liquid fertilizer. There is a 3-month rotation to soybean.
Prowl H2O 3.8CS (pendimethalin; group 3; BASF) is now labeled for used on pastures and hayfields that contain cool-season grasses with and without alfalfa (but not clovers or other legumes). The use rate ranges from 1.1–4.2 quarts/A and can be tank-mixed with other forage herbicides and can be applied in the fall, spring, or in-season between cuttings. It provides control of many annual grasses and some broadleaves but its efficacy is affected by what rate is used. Prowl does not control weeds that have already emerged. We have not done any research on Prowl for this use in forages, but we recommend a split application vs. a single, high-rate early season application. The first application (2-3 pt/A) should occur in early spring (March) but before weed germination and a second application (3-4 pt) right after first (or second) cutting to provide more residual control. An average cost for 4 pints of Prowl H2O is about $20-23/A. This is higher than what is typically spent for pasture herbicides but if annual weedy grasses are a problem, it might be worth it. There are no grazing restrictions, however immediate over-seeding of forage species to thicken the stand might be challenging since a 6-month wait is necessary to plant alfalfa and 10 months for grass species.
Resicore 3.28SE (acetochlor [Surpass] + clopyralid [Stinger] + mesotrione [Callisto] + furilazole [corn safener]; groups 15, 4 and 27; Dow AgroSciences) is a new corn herbicide premix that can be applied pre or postemergence (up to 11” corn) in field and silage corn (not yet labeled in sweet corn). It controls many annual grasses and broadleaf weeds including, common and giant ragweed, lambsquarters, annual morningglory, pigweed species, and velvetleaf. Medium soil texture rate is 2.5 qt/A. which equals a tank-mix of 2 pt Surpass + 5.76 fl oz Callisto + 0.3 pt Stinger. It may be tank mixed with atrazine, glyphosate, and many other labeled corn herbicides.
Scepter 70DG (imazaquin; group 2; AMVAC) is labeled for use in soybean. Scepter was sold from the late 1980s up until a few years ago, and then dropped by BASF and now picked up and sold by AMVAC. It is in the same herbicide family as Pursuit and Raptor and is in general, about 10-20% less active than Pursuit on most grass and broadleaf weeds. It will likely be tank-mixed with other pre herbicides to broaden control spectrum and to get a second site of action for control of ALS-resistant weeds. It does not help with burndown, but only provides residual control.
Sentrallas 1.5SC (DuPont) is a premix of the active ingredients in Harmony SG and Starane Ultra (groups 2 and 4). The use rate is 7–14 fl oz/A and it controls broadleaf weeds in wheat, barley, and oats. A similar product called Travallas 1.58SC (DuPont) is also a premix of the active ingredients in Ally, Harmony SG, and Starane Ultra (groups 2 and 4). The use rate is 7 fl oz/A for broadleaf weed control in wheat and barley.
Talinor 1.77EC (Syngenta) is an experimental premix of bicyclopyrone and bromoxynil (or Maestro/Buctril) plus a crop safener for broadleaf weed control in wheat and barley from 2-leaf to pre-boot stage at the 13.7-18.2 oz/A rate (include necessary spray additives). It can be tank-mixed to broaden control spectrum. It is not yet registered for use.
Tolpyralate (group 27 herbicide; ISK Bioscience) code SL-573 3.34SC, is a new, experimental HPPD-inhibitor herbicide for use in corn. It is similar to Impact/Armezon and Laudis as it has post activity on many annual grasses and broadleaves. It has a low use rate of 1-1.5 fl oz/A and will mostly be used in 2-pass programs or early post systems. No details yet about its trade name or when it will be registered.
Triclopyr-containing products such as Crossbow, Remedy Ultra, Garlon, PastureGard, and a new one called Vastlan. Dow AgroSciences was able to revise the label for grazing on these products. It now states that there are no grazing restrictions for livestock or dairy animals on treated areas. There was a long waiting period for lactating dairy animals that grazed on treated areas. Also, Dow has reformulated triclopyr with a new choline salt formulation which makes it a low volatile product. This new product is called Vastlan 4L and is now available on the market but has not yet been tested at Penn State.
Zidua PRO 4.09SC (saflufenacil (Sharpen) + imazethapyr (Pursuit) + pyroxasulfone (Zidua); groups 14, 2, and 15; BASF) is labeled for burndown/residual use in soybean. It controls many annual grasses and broadleaves (including marestail) and can be tank-mixed. Make sure to add MSO + a nitrogen adjuvant for burndown. Zidua Pro at 6 fl oz/A equals a tank-mix of 1 oz Sharpen + 4 oz Pursuit + 2 oz Zidua. Zidua SC 4.17L a new experimental liquid formulation of pyroxasulfone and provides good control of several annual grasses and broadleaves in corn (field and sweet), soybean, and wheat. It will have the same utility as the dry form. Both of these should be available for 2017.
Herbicide Resistant Crops
Roundup Ready 2 Xtend soybeans (dicamba-tolerant) have been developed by Monsanto to allow pre or post applications of dicamba (the active ingredient in Clarity) on soybeans. These varieties are also stacked with the Roundup Ready trait. You may recall that Xtend seed was approved for use in 2016, but few fields were planted because dicamba was not yet labeled and major exports were not yet approved at the time of soybean planting. At the same time, some adoption did occur mostly in the South last summer and the illegal use of commercial dicamba products had major problems with drift and off-target injury. Currently three dicamba-containing products have received federal and state approval Xtendimax with VaporGrip Technology (Monsanto), Engenia (BASF) and Fexapan plus VaporGrip Technology (Dupont). Each of these is a conditional, 2-year supplemental label and allows for use on RR2Xtend soybeans; however, they can be prolonged if there are few or minimal problems in the first two years. In order to reduce drift and the other negative impacts to non-target areas, the labels (and associated websites, see below) list what herbicides can be tank-mixed with these products. Other guidelines include: prescribed nozzle types, boom height, sprayer speed and wind speed limits. Also, depending on the landscape setting, field buffers must be included if susceptible crops are present and downwind at the time of application. In addition, the application cannot occur if wind is blowing in the direction of specific crops such as tomatoes, vine crops, grapes, and others. The applicator is responsible for any drift of these products to off-target sites. We see value particularly in a burndown setting for marestail control, however, we are less excited about in-crop applications and would prefer to first learn from the experiences of other states and regions in 2017 that need this technology more.
Updates will be posted online at the websites below by their respective companies:
Enlist soybean (Dow AgroSciences) is an line of genetically modified soybean that will be resistant to glyphosate, 2,4-D, and glufosinate. Also a new 2,4-D formulation (choline) is being developed that will offer ultra-low volatility, reduced drift, decreased odor, and improved handling (referred to as Colex-D Technology). The first herbicide premix to emerge will be Enlist Duo which is a combination of 2,4-D choline plus glyphosate for use over Enlist crops; other products will likely follow. No other 2,4-D formulations are expected to be labeled for use over-the-top on Enlist crops initially. At the time of preparing this article, Enlist soybeans are still awaiting approval; but is expected soon. One of the main holdups are that exports to China and EU are still not resolved yet. It is likely we won’t have it in time for the 2017 growing season. But since this is an ever-changing process, registration could happen at any time.
HPPD-tolerant soybeans are being developed independently by Bayer CropScience and Syngenta to allow the use of in-crop applications of HPPD-inhibitor herbicides (e.g., Balance Bean and Callisto). These varieties will likely be stacked with glyphosate- and glufosinate-resistant traits. Bayer’s Balance GT soybean system is expected to be launched soon. Syngenta’s MGI soybeans are targeted for later in the decade.