What’s New for Agronomic Weed Control in 2013
Posted: January 8, 2013
Instigate (rimsulfuron (Resolve) + mesotrione (Callisto); groups 2 and 27 herbicides; DuPont) is a new premix for preemergence use in field corn and contains the same active ingredients as in Realm Q. Instigate can be applied from preplant to early post (V2), and the typical soil-applied use rate is 6 oz/A. This provides some initial residual weed control of annual grasses and broadleaves, but will likely need to be followed by a post application of glyphosate (RR-corn), glufosinate (LL-corn), or conventional herbicides as needed. Tank-mix with atrazine or other products to improve control and spectrum. Watch interactions with organophosphate insecticides such as Lorsban, malathion, parathion, Counter, etc., as severe crop injury may occur. Do not apply another solo HPPD-inhibitor post herbicide (e.g., Callisto, Laudis, Impact/Armezon) to field that has been treated with Instigate in the same season.
Pyroxasulfone is a new herbicide active ingredient (group 15) that is currently labeled in corn (all types), and is expected to be labeled for use in soybeans and wheat in 2013. It has annual grass activity similar to metolachlor (Dual) and acetochlor (Harness) but also provides good control of several annual broadleaves. The use rates for the active ingredient are up to 8 times lower than Dual or Harness with comparable weed control. Penn State has evaluated pyroxasulfone for the past several years in corn and soybeans and has noted good weed control performance and crop safety. Three companies (BASF, FMC, and Valent) will sell herbicide products that contain pyroxasulfone. Below are details about each of those products.
Zidua 85WDG (pyroxasulfone alone; group 15 herbicide; BASF) provides good control of several annual grasses and broadleaves in corn. Zidua can be applied preplant (surface or incorporated) up to 45 days before planting or preemergence. Typical use rate is 2.5 oz/A on medium-texture soils; (rates can be adjusted for soil type or two-pass application programs). Corn must be planted at least 1 inch deep. Zidua does not control existing weeds and must be activated by at least 0.5 inch of rainfall prior to weed germination; otherwise, effectiveness may be reduced. Tank-mix with atrazine or other corn herbicides to broaden weed control spectrum. May be applied in a carrier of water (5 gal/A or more) or liquid nitrogen fertilizer solution (20 gal/A or more); it may be impregnated and applied on certain dry bulk fertilizers. Zidua may be applied early postemergence, but tank-mix if weeds are emerged. Expect BASF to premix pyroxasulfone with other active ingredients in the future. Zidua will we labeled for use in soybean and wheat soon.
Fierce 76WDG (pyroxasulfone + flumioxazin (Valor); groups 15 and 14 herbicides; Valent) can be used only in no-till or minimum-tilled fields where crop residue has not been incorporated into the soil and where corn will be planted directly into a stale seedbed, cover crop, or previous crop residue. Apply Fierce at 3 oz/A to field corn early preplant. Corn must be planted between 7 and 30 days after application. When applied as part of a burndown program, Fierce must be tank-mixed with appropriate herbicides and adjuvants to control emerged weeds. Fierce provides residual control of several annual grass and broadleaf weeds, but other herbicides can be tank-mixed to improve control spectrum. Do not apply to soils with less than 1% organic matter unless an activation rainfall (0.5 inch or more) has occurred between application and planting. Fierce also can be used as part of a fall burndown program. Expect Fierce to be labeled in soybeans soon.
Anthem 2.15L (pyroxasulfone + fluthiacet (Cadet); groups 15 and 14 herbicides; FMC) recently received federal registration in corn but no product labels have been released yet. Anthem ATZ 4.5L contains Anthem + atrazine. Once these products are fully marketed they will have similar utility as Zidua or Fierce. Anthem is expected to be labeled in soybeans.
Lumax and Lexar have been reformulated but still have the same utility as the old formulations for use in corn and sorghum. Keep in mind because of the new formulations, the rates may need to be adjusted. For example, Lexar EZ 3.7SC medium soil rate is 3 qt/A and Lumax EZ 3.67SC new use rate for medium soil is 2.7 qt/A. Zemax 3.67SC is similar to Lumax EZ, but contains no atrazine. The typical use rate for Zemax is 2 qt/A.
HERBICIDE RESISTANT CROPS
Enlist corn and soybean (Dow AgroSciences) are a new lineup of genetically modified crops in the Enlist Weed Control System. Enlist corn will be combined with SmartStax and thus be resistant to glyphosate, glufosinate (Liberty), and post-grass (FOP) herbicides (e.g., Assure II and Fusilade, but not Select and Poast) and have a greater tolerance to 2,4-D. Enlist soybean 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 corn and soybean varieties; other products will likely follow. No other 2,4-D formulations are expected to be labeled for use over-the-top on Enlist crops. Once approved, Dow AgroSciences estimates launch timing for this technology at 2013 for corn and 2015 for soybeans.
Dicamba-tolerant soybeans are being developed by Monsanto and BASF to allow pre or post applications of dicamba (active ingredient in Clarity, Banvel, etc.) on soybeans. These varieties will be part of the Roundup Ready PLUS Weed Management Solutions system and will be stacked with the Roundup Ready trait. In addition, a new next-generation, lower volatility dicamba formulation, called “Engenia”, is being developed for use in this system. To the best of our knowledge, it is a BAPMA, polyamine salt formulation. If approved, this system will likely be available mid-decade.
In general, there are some benefits and risks associated with Enlist and dicamba-tolerant technologies. Overall, we can expect to see better annual and perennial broadleaf weed control in soybeans. Also these traits will offer some protection from drift and spray tank contamination. However, off-site movement of 2,4-D and dicamba to sensitive non-target plants remains a concern. In a diverse landscape like Pennsylvania, this will be more of a concern than perhaps for our neighbors to the west. We understand that the companies involved in developing these technologies are devising special stewardship guidelines on nozzle type, spray boom height, ground speed, wind speed, sensitive crop buffers, among others. Also managing volunteers in rotational crops will become more complex. Over the next few years, we will see how these companies and universities devise ways to handle these issues.
HPPD-resistant soybeans are being developed by Bayer CropScience and Syngenta to allow the use of in-crop applications of HPPD-inhibitor herbicides (e.g., Balance, Laudis, and Callisto). These varieties will likely be stacked with glyphosate- and/or glufosinate-resistant traits. This system is expected to be launched by 2016 or possibly earlier.