Given the difficult 2019 season and resulting weed seed production, weed populations could potentially be higher in 2020 compared to previous years. When considering weed control programs, keep in mind both the short range goal of controlling weeds so they are not yield limiting, and also the long range goal of weed seedbank depletion.
Good control following seasons in which weed escapes were high will both preserve short term yield and have long lasting effects by diminishing the weed seedbank.
If you are in the process of making vital herbicide decisions for your corn acres, check out the Economics of Commercial Weed Control Programs in Corn from Michigan State University. Each year, the MSU weed science team asks herbicide companies to submit up to four weed control programs for the study based on soil type and weed infestation history. In 2019, 24 herbicide programs were evaluated (Table 1).
Use Table 2 to compare how your current corn herbicide program fits into the broad spectrum of commercial programs available. Results in Table 2 include corn injury, weed control, program costs, corn yield and economic returns of the 24 herbicide programs evaluated.
Overall, 23 of the 24 herbicide programs tested resulted in greater than 90% control of all weeds prior to harvest. Twenty-three of the 24 herbicide programs resulted in statistically similar yield. The maximum yield in this trial was 233 bushels per acre, and yield was 83 bushels per acre in the untreated (weedy control) treatment. Weed competition in this trial resulted in a yield loss of 150 bushels per acre (64%).
Twenty out of the 24 herbicide programs resulted in statistically similar gross margins. The maximum gross margin in this trial was $838.25 per acre, and the gross margin in the untreated weedy treatment was $311.91 per acre. Weed competition in this trial resulted in an economic loss of $526.34 per acre (63%).
In addition to the 2019 economics of commercial weed control programs in corn, you can also find results for soybean (non-GMO, convention till and no-till) dating back to 2004 on the MSU Weed Science website.
When designing herbicide programs to delay the evolution of and battle herbicide resistant weeds, the first step is to make sure your program utilizes multiple effective sites of action. The herbicide site of action refers to the location or enzyme where the herbicide acts to disrupt plant growth.
Herbicide sites of action are numbered and can be found on the herbicide label or in the 2020 MSU Weed Control Guide for Field Crops. I took the treatment list for all herbicide entries in the corn commercial comparison trials from 2006-2019 and tallied the frequency of sites of action used (Table 3).
Overall site of action group numbers 5 (e.g. atrazine), 15 (e.g. Dual, Outlook, Harness) and 9 (e.g. glyphosate) were used most frequently overtime. Further, I took the treatment trade names for all herbicide entries in the corn commercial comparisons trials from 2006-2019 and created a word cloud, which is a visual representation of the treatments and highlights the frequency of the treatments included in the study overtime.
When interpreting a word cloud, the treatments that are larger and are the same color were included more frequently in the corn commercial comparisons studies from 2006-2019 than those that are smaller. Not surprisingly, glyphosate (e.g., roundup) was the most frequent treatment followed by atrazine.
Editor’s Note: For accompanying tables, please see original article at the Source URL below.