Not too long ago, I received a telephone call from a colleague who asked me the following question: “How hard might it be to manage weeds in field corn without Roundup or Liberty?” Obviously, this question was prompted by the current supply shortages and subsequent massive price increases of some herbicides.
Before I go any further, I would like to remind younger growers, or Roundup babies, that before the late-1990s, most growers were doing just fine (in most cases but not always) without the RR or LL technologies. There is no doubt that these herbicide-resistant crop weed control technologies bring much to the table, including making weed control somewhat easier and providing better control options for difficult weed species.
With some thoughtful preplanning, I am confident you can build a reasonable field corn weed control program without Roundup or Liberty if need be.
Atrazine has been and should continue to be the foundation of field corn weed control. For about $5 per acre, or two quarts per acre of 4L formulation, atrazine provides some of the best and cheapest weed control available. Another benefit of atrazine is that field corn tolerance is excellent to both preemergence (PRE) and postemergence (POST) applications. Some might argue that over the last few years, atrazine has slipped on Palmer amaranth control. Although this may be very true in some areas, atrazine still provides outstanding residual and POST control of many other weed species.
If you have not been using any WSSA-MOA Group 15 herbicides (such as Anthem Maxx, Dual Magnum, Outlook, Warrant, and Zidua) in field corn, now is a good time to get acquainted with them. Generally, herbicides in this group provide effective residual control of annual grasses (less on Texas panicum) and Palmer amaranth. These products can also be applied PRE or POST, but I would prefer that Anthem Maxx and Zidua only be applied POST in order minimize crop injury.
If you have ever heard me give a talk about field corn weed control, I always mention Prowl/Prowl H2O. Prowl/Prowl H2O should/could be applied POST with other herbicides to increase the residual control of one of the most infamous field corn weeds, Texas panicum (a.k.a. bullgrass or buffalograss).
POST field corn herbicide options are aplenty. I have included a list of these older/newer products that I have been testing for several years (Table 1). Also, check out Figure 1 from my 2021 research trials (no Roundup or Liberty).
If you just cannot help being a Roundup or Liberty junkie, I have heard from some of my covert industry contacts that premix formulations such as Sequence (Roundup + Dual Magnum), Halex GT (Roundup + Dual Magnum + Callisto), Sinate (Liberty + Impact), and others(??) might be in good supply. I suggest that you contact your local dealer ASAP about their obtainability.
Based upon what I have heard in the rumor mill, I am not sure how much field corn will be planted in the southeast in 2022 due to excessive fertilizer prices. If you decide to plant field corn and are frustrated with the availability and/or current prices of Roundup and/or Liberty, you have numerous options to consider for weed control. Now is a great time of year to get those plans in order especially if you are unfamiliar with the products. With some loosening’s in COVID-19 restrictions, I look forward to seeing you in person at a local county extension meeting this winter.
As always, good weed hunting!