Due to little time and very few good spray days, some corn fields have yet to have their layby application. Corn is putting on a new leaf every 3 days with all the heat and water. Therefore, time is short before it will be too mature to many herbicides safely over the top. Continue reading
JACKSON, Tenn. – The University of Tennessee Institute of Agriculture will host the annual Weed Tour June 18 at the West Tennessee AgResearch and Education Center. The guided tour will feature 60 weed management research tests in cotton, corn and soybean.
Weed Tour runs from 9 – 11:30 a.m., with registration opening at 8:30 a.m. Continue reading
Crops injured by off-target herbicides have been too numerous for this early in the year! The most frequent problem has been corn injured by clethodim. There have been more reports and observations of this in the past 3 weeks than I can recall cumulative the past 20 years.
In my opinion, there are three reasons. First, with glyphosate no longer working on 5 grass species, clethodim is now used like never before as the “go to” for burndown. Second, with all the frequent rain there have been few days to spray causing applicators to rush. This in turn leads to higher probability of poor sprayer clean out and applications in less than ideal conditions. Third, small corn is highly susceptible to clethodim and it takes very little exposure to kill corn (Picture 1). It takes even less to cause bleaching and malformed whorls. Corn with these symptoms often will not die but may not produce an ear (Picture 2).
TDA has also gotten numerous complaints about 2,4-D drift. Most of this has been drift from pasture applications or burndowns.
Finally, a few dicamba drift issues have just recently been reported. The soybeans I have witnessed showing dicamba injury apparently were from burndown applications nearby.
I bring all this up to note that we are now in June. This is the most difficult month to keep herbicides in the targeted field as not only can they depart with wind but also through volatility with the higher temperatures this month.
Judging from the issues in May, we clearly need to up our game with respect to stewarding herbicide applications so the correct herbicide goes on the correct field. Remember the fundamentals of good herbicide stewardship: Wind speed, wind direction, applications with drift reduction agents added, sprayer boom height within 24” of the crop, etc.
Most importantly, use herbicides LABELED for use on the particular crop in the field. Only use Enlist One in Enlist crops. Never use the ester formulation of 2,4-D on pastures in the summer (Ester before Easter).
Finally, dicamba no longer has a label to be applied over Xtend crops and should not be used. Fortunately, Liberty Ultra in our research and also in fields I have walked has performed much better on pigweed so far this year than I would have anticipated. That new formulation looks to be providing more consistent Palmer amaranth control across various environmental conditions than the older 280 formulations.
This has been a tough week, with many walking cotton planted in mid to late May to find stands thinner with more gaps than acres planted in April. The number of cotton acres within the state appears to be decreasing despite several growers still planting. Subsequently, in the past few days, I’ve had calls complaining about seedling vigor of every commercial cultivar. Unfortunately for us, seedling vigor and seed quality have almost nothing to do with the failed stands from our last planting window- even marble-sized seed of the highest quality will drown when forced to suffer through prolonged saturated conditions. That said, a few callers this week pointed to one cultural practice as the saving grace on their acres, with others mentioning their desire to incorporate the practice on some of their acres in the future. In this blog, I’ll describe the underlying reasons for why that practice may only fit a portion of our acres- but for the acres on which it fits, it rarely results in the need for a replant. I’ll also talk briefly about the lessons those who cannot use the practice might apply to their acres.
The slider above includes two pictures of cotton planted by the same planter, on the same day (May 22, 2025), within the same field (Milan, TN)- the two areas are approximately 200 ft apart. Click and hold your pointer over the dividing line and slide it back and forth to see the striking differences associated with bedded versus flat ground this year. Continue reading
Most of the conversations I’ve had in the past few days have centered around what to do with thin stands, when to stop planting, and how to manage late planted cotton. In this post, I’m going to try to briefly tackle these three topics. Be prepared, my opinion on a few of these items may run counter to the opinions of others. Spoilers- if in doubt, keep it; yield potentials begin to decline rapidly as we move into June; and June cotton should be planted thinner than April or May cotton. Continue reading
What began in March as a quick start to the planting season has with the many frequent rain events turned into a very slow struggle. The question of the hour is on how to burndown fields that are grown up messes before planting soybeans (Picture 1 and 2). There are strategies that can tackle fields that are heavily infested with 3’ tall goosegrass, Palmer amaranth, horseweed and volunteer corn. They typically require some kind of sequential application to be successful.
Paraquat, the usual “go to” for late spring burndown, will not control grasses with size, horseweed or even pigweed that has gotten so far out of hand. As such, the best approach is aggressive tillage. That unfortunately is not an option on our highly erodible fields.
In those cases, a tankmix of a high rate of Liberty plus clethodim is the best approach to try to control the grass weeds, horseweed and set the pigweed back. Then, if possible, a couple days later apply paraquat. This approach would have the best chance of success with herbicides.
In fields where the soybeans may emerge before a follow-up paraquat application could take place then Liberty tankmixed with Enlist should take out any escaped broadleaves. If grass seems to be recovering then apply Liberty plus clethodim.
The UT Cotton Scout School is scheduled for Wednesday, May 21st, at the West Tennessee Research and Education Center (605 Airways Blvd, Jackson). There is no fee, and preregistration is not required. Registration begins at 8:00 AM with the program starting at 8:30. Pesticide points in categories 1, 4, 10 and 12 will be offered and a BBQ lunch will be provided. Content will include classroom and hands-on training with an optional go-to-the-field session after lunch. Topics covered will include cotton development and identification and symptoms of insect pests, plant diseases, and weeds.
Due to little time and very few good spray days, some corn fields have yet to have their layby application. Corn is putting on a new leaf every 3 days with all the heat and water. Therefore, time is short before it will be too mature to apply many herbicides safely over the top.
How large can corn be before glyphosate could potentially cause injury? The glyphosate label states it can be applied up through the V8 corn growth stage. My experience has been if glyphosate is applied to corn larger than that it can at times cause ears to be barren. This phenomenon is difficult to predict ahead of time as it can vary due to maturity of the corn at application, hybrid and weather.
Crop stage and/or crop height is used to determine the cutoffs for a given herbicide. Often the label states the limits at whichever (crop stage or crop height) comes first. Crop stage can easily be done by counting the number of leaf collars that are fully exposed (Ex: 4 collars = 4 leaf) (Picture below). If tankmixing, cutoff is always determined by the most limiting factor.
Johnsongrass Escaping Glyphosate Burndown
| Postemergence Corn Herbicides | Crop Height Cutoff | Crop Stage Cutoff |
| Accent | 20 inches | 6 leaf |
| Acuron GT | 30 inches | 8 leaf |
| Atrazine (Bicep, Degree Xtra, Acuron, etc.) | 12 inches | – |
| Callisto* | 30 inches (without atrazine) | – |
| Capreno* | 20 inches | 7 leaf (without atrazine) |
| Corvus | 2 leaf | – |
| Dicamba (Clarity, etc.) | 8 inches (1 pt/A) or 36 inches (1/2 pt/A) |
5 leaf
– |
| Distinct | 24 inches | – |
| Glyphosate – RR corn only | 30 inches | 8 leaf |
| Halex GT | 30 inches | 8 leaf |
| Armezon/Impact | – | 8 leaf |
| Laudis | – | 8 leaf |
| Liberty – LL corn only | 24 inches | 7 leaf |
| Diflexx | 36 inches | 10 leaf |
| Realm Q | 20 inches | 7 leaf |
| Resicore REV | 24 inches | – |
| Resolve Q | 20 inches | 7 leaf |
| Roundup PM – RR corn only | – | 8 leaf |
| Shield Ex | 20 inches | 6 leaf |
| Status | 36 inches | 10 leaf |
| Steadfast Q | 20 inches | 7 leaf |
| Storen | – | 8 leaf |
| 2,4-D | 8 inches | – |
*Note that if atrazine is added to herbicides such as Callisto or Capreno for example, the cutoff would be reduced to 12 inches.