Picture 1. Grass and Palmer amaranth escaping paraquat burndown in emerged cotton
There have been numerous fields where goosegrass, junglerice and Palmer amaranth were not controlled at burndown and the crop has emerged. In some cases, the wet weather delayed burndown to where Palmer amaranth and those grasses were too large to be effectively controlled with one pass of Gramoxone (Picture 1). In other cases, tillage used to help speed up field drying or to build beds partially buried pigweed and grasses which make effective burndown from Gramoxone very problematic (Picture 2). In a few cases, dicamba and glyphosate were used for burndown and they did not control those weeds due to resistance (Picture 3). Continue reading →
The call of the last week was Pre-emerge herbicide injury in soybeans. Several folks reported that their soybeans were “going backwards”. This is not a surprise as in wetter springs the probability of seeing injury from Pre-applied herbicides is greatly increased. That coupled with an increase in soybean acres this spring would increase the probability of herbicide injury in that crop. I would expect more of the same as we move into June with all the rain in the past few days.
In almost every cotton-related conversation I had during early May, the conversation quickly turned to our excellent early planting window- a window which opened earlier in 2024 than any of recent memory. Since then, most have fought to find an opportunity to mud in any acres and many are now considering shifting some farms to soybeans. In this blog, I attempt to cover yield potential of a late planted cotton crop and highlight several very important factors to consider when planting cotton at the end of our ‘normal’ planting window. Continue reading →
Carryover injury from fomesafen (Flexstar, Prefix, Reflex, Intimidator, Marvel, Dawn, Rhythm, etc.) is starting to show in a few corn fields. This is because some applications in late June and July in 2023 coupled with a very dry fall allowed the herbicide to persist into winter. Recent rains then allow any herbicide carryover to more completely get into the soil solution.
Fomesafen carryover injury in corn and grain sorghum looks similar. Expect to see stunting and interveinal chlorosis as pictures below sent from crop consultants clearly shows.
Striping of corn leaf veins characteristic of fomesafen carryover
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.
4 – Leaf Corn
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
11 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.
Zidua (pyroxasulfone) applied via impregnated fertilizer in cotton has become popular in Tennessee. My understanding is that about 25% of the cotton acres last year had Zidua applied in this fashion. With the increasingly poor Palmer amaranth and grass control we are experiencing with dicamba + glyphosate, overlaying residual herbicides must be the foundation for weed control. Continue reading →
The EPA is soliciting public comment on a registration review decision where the EPA proposes to cancel all uses of acephate, except for injections to non-food bearing trees. Acephate is widely utilized in Tennessee row crop agriculture and is a critical component of IPM programs. Cancelling an important crop protection product would place increased pressure on a limited number of control options available to producers. We are encouraging agricultural professionals to comment to the EPA on the impacts acephate has on your production systems. If you need assistance with comments please contact your UT extension specialist. The link to comment is below. Deadline for comments is July, 1, 2024.
The UT Cotton Scout School is scheduled for Tuesday, 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.
