VanGessel: Proactiveness shouldn’t be in short supply

Mark VanGessel, University of Delaware Extension weed specialist, urged listeners during Delaware Ag Month’s Agronomy session to consult the updated 2022 Mid-Atlantic Weed Control Guide for weed control information, as he did above at a 2021 UD field crop tour. (Photo courtesy University of Delaware)

What if there is a shortage this year of glyphosate and glufosinate?
Manufacturers are talking about it, which is often interpreted to mean they will not be available.
They will be available, Dr. Mark VanGessel, University of Delaware Extension weed specialist, told listeners during Delaware Ag Month’s Agronomy session, but there may be tight supplies, not just of Roundup and Liberty but all brands, including pre-packaged mixtures.
“Talk to your dealer so you know how much you can expect, and maybe get delivery early,” he said.
At the time of VanGessel’s presentation Jan. 13, there were no changes to dicamba products for soybean for 2022. Farmers still have tank mixes and adjuvants, VanGessel said.
What can be used has not changed. Buffers are still in place. The annual training requirement has not changed.
“After June 30 these products cannot be applied to soybeans,” he noted. “EPA looked at dicamba hard this past fall, in light of the continued issues with off-target movement in the Midwest. Just before Christmas, they released a statement that said the regulatory tools that the agency could use to address the extent and severity of alleged dicamba-related incidents are unlikely to be imposed or fully implemented by the 2022 growing season due to statutory processes agency is required to follow.”
He added, “I’m not quite sure how to interpret that … so I would keep my ears to the ground as to what might be going on.”
On Jan. 11, the EPA granted a new seven-year registration for Enlist. It is the first herbicide registered at the EPA with a fuller integration of the Endangered Species Act. Precautions emphasize preventing herbicide movement through rain and irrigation water.
They want to ensure the products are not leaving the field through lateral flow or runoff of the water. The restriction is not to apply if a significant rainfall is expected within 48 hours of application.
On the flip side, VanGessel said, irrigation or rain shortly after application can, in many cases, improve activity of the product getting into the plant and making sure plants don’t have environmental stress.
The other emphasis is avoiding pollinator exposure.
The cutoff timing on Enlist has been moved from R2 to R1 (earlier) so pollinators are not in the field. It’s a cut off stage, not date, based on the soybean.
Mandatory training is now required. Since it was just announced, final labels are not available. “Stay tuned,” VanGessel said.
There is still a 30-foot buffer to sensitive areas. Check the website for adjuvants, tank mixtures and required nozzles for use, he said.
With anticipated shortages, grass control may be a challenge.
There is documented reduced grass control when Group 1 herbicides (Poast, Select, Assure and so forth) are tank mixed with dicamba or 2,4-D, regardless of formulations. Dicamba alone will not control grass. So if grasses are in the field and glyphosate is not included in the spray mix, that’s something we’re going to have to contend with and plan accordingly, VanGessel said.
If glyphosate is in short supply, you’ll want to prioritize use in difficult fields where you have struggled with weed control, including grassy weeds; fields hard to treat timely; fields being rotated to vegetables. VanGessel said he thinks glyphosate is going to be more valuable in soy than corn.
He also suggested farmers pay attention to use rates and target rates that are appropriate for weed size instead of just using a generic 32 fluid ounces. For example, the maximum rate of Roundup PowerMax is 32 fluid ounces. For fall panicum and velvetleaf that are 12 inches high, use the full rate. If they are 6 inches high, use 22 fluid ounces, he suggested.
Be sure to match the product to the right rate, he added.
The weight of an active ingredient in glyphosate products is the weight of the acid as well as salt and will vary based on the salt formation. Whether using Roundup PowerMax3, PowerMax, GlyStar 5 Extra, Durango or Makaze, you need to know how much acid equivalent you are getting.
“Remember, you’re not replacing gylphosate, you’re using different products,” he said. “We’re using different herbicides which have different requirements in terms of application. Oftentimes these are not as effective on larger wheat so it’s really important that we apply them at the right time.”
He continued, “Prior to Roundup Ready soybeans, we used sequential paraquat applications. Paraquat is not as effective for soy burndown because the weeds are bigger.”
VanGessel has found over the years for consistent control, particularly in fields infested with marestail, it helps to go out early for burndown.
But if you spray four weeks before planting soybeans, you’ll have weeds that emerge between then and planting, so you may need another application at planting.
If you don’t have enough glyphosate to go around, VanGessel said using 2,4-D or dicamba in combination with Canopy EX or Synchrony over the years has been a pretty good program in many cases. But then it needs to be followed up with paraquat plus metribuzin, which improves the performance of paraquat, and then with additional residuals at planting.
But this program does not control grasses, he said. “If we include a grass herbicide, we see antagonism” (where two or more herbicides in a tank mix produce poorer weed control than the individual herbicide components would supply alone).
For grassy fields, he recommended farmers prioritize their weed problems and fields, and use glyphosate where they will get the best bang for their buck.
With cover crops, you could stretch glyphosate supplies by delaying termination of the cover crop from four weeks pre-planting to 10 to 14 days before planting, so only one burndown application is needed.
He referred to two publications that contain identical weed information. The Agronomy Guide from Penn State, published every two years, is available from 2021.
Some of the updates may not be in there, but are contained in a smaller publication, the 2022 Mid-Atlantic Weed Control Guide, also available from Penn State. Order online at extension.psu.edu/publications or call 877-345-0691.
Virginia Tech’s 2021 Field Crops Pest Management Guide (VCE Publications 456-016) is available free online at https://www.pubs.ext.vt.edu/456/456-016/456-016.html.
A hard copy is available for a fee. Contact vceresources@vt.edu for details.
It’s surprising how little change there has been since 1996, VanGessel said. Some are quite noticeable, but the active ingredients have changed only a little.
VanGessel left his audience with a number of factors to consider, particularly if there’s a glyphosate shortage: Are tank mixes needed? Is that pre-mix a sufficient ratio? These are often formulated for the Midwest and may not be appropriate for our area.
Are you using the right adjuvants? The right nozzles and droplet size to get the right spray volume? Is there antagonism or potentially enhanced control?
For effective weed control, start clean. Use the right products for the weeds present. This often requires premixes or tank mixes.
Apply at the right rate (labeled rate) and right time. Make sure you are relying on experience or using our resources like the Mid Atlantic Weed Management Guide or the same information from Virginia Tech.
Use nonchemical integrated strategies as much as you can, such as:
• Focusing on preventing weed seed production of troublesome species.
• Rotating crops so you can you rotate chemistry.
• Maximizing the competitiveness of crops to improve weed control by using good agronomic practices and using narrow row spacing to get a tighter canopy quicker.
• And, cleaning equipment between fields so weeds aren’t spread from field to field with the combine.
Finally, VanGessel recommended a website on integrated weed management, growiwm.org, a collaborative effort his group is involved with.