It is believed that human/weed interactions accelerated at the inception of agriculture! Prior to 1996, weed control in some crops was a major challenge. There was a running joke in the 80s and 90s (probably earlier) that available herbicides at that time were so tough on soybeans, one needed to avoid the sprayed field for a week or two to avoid seeing how miserable the plants looked! Similarly, weed control in sugar beet relied on the ‘micro-rate’ system under which a combination of herbicides was applied weekly at reduced rates. Like the case with soybeans, sugar beet plants looked very ‘tortured’, chlorotic, and stunted for weeks. Once the root system grew below the treated soil, plants improved, but yields were often low reflecting early herbicide injury. Things changed in 1996 when glyphosate-resistant soybeans were commercialized in the United States. Likewise, weed control in sugar beet was ‘revolutionized’ with the commercialization of glyphosate-resistant hybrids in 2007. The adoption of glyphosate-resistant sugar beet was almost 100% within a season of commercialization!
However, the overreliance on glyphosate, which included multiple in-season applications, quickly selected glyphosate-resistant weeds. Initially, it was Palmer amaranth (‘the king of weeds’) and waterhemp in the mid-western states, and later kochia in the western states including Idaho and Oregon. The industry response to weed resistance to herbicides has largely been to generate crop hybrids resistant to multiple herbicide modes of action. Sadly, weed resistance has evolved within a short period of their introductions.
Advances in genetic transformation of plants and breeding techniques have facilitated the development of herbicide-resistant crops often involving resistance to multiple herbicides (called stacks). The recent entrant is sugar beet hybrids resistant to applications of three herbicide products: glyphosate, glufosinate, and dicamba (dubbed ‘triple-stack’) developed by KWS® Seeds, LLC in cooperation with Bayer®. The triple-stack trait is nicknamed ‘Truvera®’. Starting in 2021, scientists in several states including Idaho and Oregon have been conducting regulated studies to evaluate the performance of the Truvera® trait including fitness to local production practices and weed control. The regulated studies are monitored by the EPA and APHIS. The technology is similar to that already commercialized for cotton. The development of this trait remains on track for the estimated launch at the ‘middle of this decade’.
Glufosinate (e.g. Liberty 280 SL ®, Rely 280®) is a nonselective postemergence (POST) herbicide originally developed as a “burndown” to control vegetation at planting in no-till or stale seedbeds, and in non-crop situations. Advances in genetic transformation have facilitated development of glufosinate-resistant plants including corn, cotton, rice, soybean, and now sugar beet. Because glufosinate acts faster (with visual symptoms evident within 10 hours) than glyphosate, the two products are never mixed or applied together.
Dicamba is a member of the benzoic acid family of herbicides but more widely grouped as a synthetic auxin (Group 4), which includes 2,4-D type products. Dicamba has been used for broadleaf weed control in corn, small grains, and pastures for over 50 years. It has a penchant for off-target movement as a drift at the time of application, extended off-target post application by volatilization, physical soil particle movement, or spray tank contamination. However, the dicamba formulation currently being tested includes the ‘VaporGrip’ technology that reportedly reduces off-target movement.
The recent iteration of dicamba being evaluated for use in sugar beet is a restricted use herbicide being sold under the tradename ‘XtendiMax with VaporGrip’ and at the time of writing this article, it is not registered for use in the Pacific Northwest region.
Field studies indicated pre-emergence (PRE) application of XtendiMax provides ≥14 days of soil activity to manage weeds in sugar beet. However, as of 2022, studies are not being taken to yield. The effectiveness of PRE-application of XtendiMax was observed across the test sites in MI, ND, MN, NE, WY, ID, and OR where studies are being conducted. Similar results have been observed in other crops including soybean and cotton. PRE application seems very effective to manage weeds and may lessen the potential for drift to sensitive crops not planted at the time of application. Postemergence applications starting when sugar beets are at 2-leaf stage will include tank mixes with glyphosate (but not glufosinate), volatility reduction adjuvant, drift reduction adjuvant, specific nozzles and spray water volume. Standalone POST applications of glufosinate are also being evaluated.
Stay tuned for future test results as studies continue!
This article may contain forward-looking statements based on current assumptions and forecasts made by Bayer management. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. These factors include those discussed in Bayer’s public reports which are available on the Bayer website. The company assumes no liability whatsoever to update these forward-looking statements or to conform them to future events or developments.