Most soybeans in Tennessee are now planted in 15 to 7.5” rows. This can help on weed control as the soil is shaded more quickly. Shaded soil will reduce weed seed germination rates. A good PRE-applied herbicide coupled with narrow rows and effective POST applied options is a very sound weed management strategy.
However, in fields where Palmer amaranth is resistant to POST over-the-top herbicides, planting in wide rows and using a cultivator or hooded herbicide application can be an effective weed management option. Continue reading →
All the frequent rain through June has made it nearly impossible to spray fields even close to timely. This has left many cotton fields with large goosegrass and Palmer amaranth. The typical post application to control both those weeds is a tankmix of Liberty and clethodim. This tankmix can often provide fair control of large goosegrass. However, Palmer amaranth too often will recover. In those cases, hooded or post-direct applications should be Continue reading →
The weather forecast, if accurate, suggests next week will dry up enough where we all can get back in the field. Everyone will need to be running sprayers as weeds have not stopped growing. I know everyone will be in a rush, but please, please take the time to be good stewards and apply herbicides as directed by the labels. Continue reading →
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. 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 →
(Picture 1 ) 3 foot tall goosegrass, fall panicum and Palmer amaranth that need to be burndown before soybean planting(Picture 2 ) Delayed burndown: Large Horseweed and Palmer amaranth
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.
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 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.
