(ED - This article first appeared in Amalgamated Sugar Company’s Sugarbeet Magazine. It is reprinted here with permission.)
Weeds have been a part of farming forever. In fact, farmer or not, weeds have been a part of nearly everyone’s life. Whether it’s pulling them out of Grandma’s flower bed, spraying roadsides for the county, or catching grasshoppers as a kid, weeds have had a direct impact on every one of us at some point or another.
As for defining weeds, there are a myriad of definitions from “a plant out of place” to “any non-native plant that can disrupt a community,” or a personal favorite, “a plant whose virtues have not yet been discovered.” Whatever your personal definition of weeds happens to be, one thing is certain - getting rid of them tends to take up a lot of time and effort that frankly, most people would rather be directing somewhere else. When it comes to crops, that time and effort can really impact the bottom line.
Weeds create many problems in cropping systems. For starters, many early season weeds become established earlier than our crops do – sometimes long before a tractor is even in the field, costing us time and effort to clear them before a crop can even be planted. They can also cause issues later in the season. For example, in furrow irrigated systems, they can block water from reaching the end of the field. Or conversely, they can keep areas of the field too wet because of shading, leading to things like root rot. As plants, weeds compete for sunlight, water, and valuable nutrients that our crops need to grow and thrive. Additionally, weeds can serve as alternate hosts for pests and diseases affecting our crops and many have the potential to leave a very hefty seedbank if left unchecked.
Over the past couple of years, Mother Nature has dealt Amalgamated Sugar growers some hands that have undoubtedly made weed control tough for some. Cold and windy conditions in spring deter many applications of herbicides when it really could count. As the season progresses, early summer heat has led many to lean hard on watering their crops but hindering the ability to get a spray rig out in a timely manner. Dry summers contribute to dust that gets deposited on the leaves. That dust then creates a barrier to chemicals needing to get on/into the leaves of the plant, essentially rendering herbicides useless.
Currently, and for the foreseeable future, supply chain complications and chemical prices will certainly serve as an important variable when it comes to management decisions on the farm. Understandably every farming operation is different and there are many reasons a grower can’t (or won’t) get out to spray weeds at one time or another. But, for all of the reasons not to spray weeds, there are an equal number of reasons why a grower SHOULD make every effort to maintain a solid and consistent weed control program – especially in sugarbeets.
Any beet grower will say that beets are not very competitive as they are coming out of the ground. As seedlings, they are very susceptible to competition from other plants. Research has even shown that sugarbeets have the ability to “detect” whether other green plants are present within the immediate vicinity. When other plants are detected, sugarbeets will alter their growth pattern accordingly and send more energy into top growth to avoid being shaded. In unrelated studies, research has also shown that to maximize yield in sugarbeets, the crop needs to be kept weed-free for at least the first eight weeks after planting. The time between emergence and row closure is the most critical time for growers to focus on controlling weeds as the amount of bare ground or “opportunity” for weed establishment is highest.
Additional studies have demonstrated that only a small number of kochia, lambsquarters, or pigweed plants, (about 4 plants per 100 square feet) are needed to significantly decrease the yield of a sugarbeet crop. Four plants per 100 square feet can mean the difference between a 45-ton beet crop and a 36-ton beet crop, or around $450 per acre.
Several years ago, research was done by Amalgamated Sugar on the economics of skipping a herbicide treatment. Based on a standard plan with three applications of Roundup Powermax, some with a pre-plant burndown, some without, the research concluded several key things.
- Planting into a clean seedbed is highly beneficial, especially if extenuating circumstances prevent another treatment from being made until much later (i.e. 8-10 leaf).
- Treatments between 2 leaf and 8 leaf are critical for maximizing yield and profitability of the beet crop.
- The amount of yield lost due to skipping just one treatment between planting and row closure was at least double the cost of the application itself.
The moral to the story is that the benefits of spraying, even when the crop doesn’t look like it needs it, outweigh the bad.
As more challenges continue to press down on growers’ ability to exercise a smooth weed control plan in sugarbeets, it may be time to reflect on our past in order to stay ahead of the curve and move towards the future with confidence. The aforementioned supply chain complications and chemical prices, along with tightening EPA regulations, and resistant weeds are not going away any time soon. Our ability to adapt as growers and weed managers will define our success. Despite the sensitivity of sugarbeets to many chemicals in the marketplace, growers are fortunate to have multiple residual herbicides labeled and proven for the crop that can be used to help our glyphosate do some heavy lifting.
Looking at the season ahead, growers might consider a change in their weed management plan that takes advantage of some of these residual chemicals. Ethofumesate (Nortron), dimethenamid-P (Outlook), Triflusulfuron (UPBEET), S-metalochlor (Dual Magnum), and acetachlor (Warrant) are a few examples of products labeled for beets that will provide good residual control of many of our problem weed species. Clethodim (Select Max) or sethoxydim (Poast) will also aid glyphosate in controlling many problem grasses. Using modes of action besides that of glyphosate will not only be a large benefit in combatting weed resistance but will help many growers stretch an already short supply. For some, now may also be a good opportunity to dig out some of the old Sugarbeet Mix that has been taking up space in so many sheds.
Regardless of the management plan decided upon, four things should be a part of every plan.
Plant clean. The ability to start clean will give a crop the head start it needs in the race to canopy closure. Not having the need to compete for valuable sunlight, water, and nutrients will ensure the beets have what they need from the beginning.
Timing is key. Growers have all heard the saying, “Weeds are best controlled when you can’t see them.” The biggest advantage any applicator can give the chemicals they are applying is spraying when the weeds are small. Small weeds mean greater ratio of chemical to plant biomass and when the plants are young and most susceptible to the chemicals.
Adjuvants. Proper adjuvants and conditioners go a long way in ensuring complete coverage and efficacy of the chemicals being sprayed. Hard water tends to antagonize many active ingredients, including glyphosate, so an ammonium sulfate (AMS) or similar product is recommended. Some product labels suggest the use of a crop oil (COC, HSMOC, MSO) or nonionic surfactant (NIS) for best performance. Don’t stray away from these chemicals as they are suggested for a reason.
Control Escapes. Escapes can mean several things. They can be a result of conditions unsuitable for spraying, a plugged nozzle, resistance to a certain mode of action, or maybe a weed just got missed. In any case, control escapes immediately. If possible, use a different product than the one previously sprayed to control it. Our low incidence of resistance in our area is largely due in part to a diverse crop rotation, but also to growers’ vigilance in controlling these escapes before they can reproduce. The importance of combating resistance, especially glyphosate resistance is paramount for the future success of our Roundup Ready sugarbeet technology.
As growers embark on a new cropping season (and a new season of weeds), the importance of weed control will be high – especially after the seeds deposited by last year’s weedy season begin to germinate. Just like weeds are the gift that keeps on giving, following a solid proactive weed control plan in all crops will ensure success for the entire farm year after year.