Last fall there was a notable amount of Palmer amaranth in many corn fields in areas of the state where we had confirmed dicamba resistance. As a result, we have recently conducted some field screens on these pigweed populations to herbicides used in corn and soybean.
Figure 1
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.
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.
https://www.regulations.gov/docket/EPA-HQ-OPP-2008-0915/document
EPA-HQ-OPP-2008-0915
Palmer amaranth emergence is very rapid now. This is about a month early for Palmer emergence to be at this pace in Tennessee. With the spread of dicamba resistance in our Palmer amaranth population Liberty is our last best hope to control dicamba-resistant pigweed escapes in cotton and soybean. This is just a quick reminder that the time of day that Liberty is applied has a large determination on the success or failure of that application. Continue reading
It is apparent from numerous calls that many growers this spring are planning to cut rates on PRE-applied herbicides in soybean and cotton. I can understand the mindset with the depressed commodity prices, however I fear it may be the catalyst for Palmer amaranth history to repeat itself. Continue reading
Large patches of Johnsongrass that have gotten through glyphosate burndown are now very prevalent in many fields. This is particularly noticeable in several southeastern counties of West Tennessee where some of the Johnsongrass has shaken off burndown and now is almost waist high in some cases. The main threat with Johnsongrass is in corn where there are few POST applied options. Continue reading
A good many reports from the field reflect what our research this spring has shown. In short, clethodim is the herbicide of choice to control ryegrass. Often clethodim tankmixed with glyphosate can improve the probability of better overall control. Ryegrass control with glyphosate alone is much more hit and miss both in our research and in many fields this year (Picture 1). Continue reading