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How to Properly Use Dicamba on Soybeans

read farmdocdaily article

As the growing season approaches it is important for farmers to understand how to use dicamba on resistant soybean varieties. Todd Gleason has more with University of Illinois weed scientist Aaron Hager.



The following is an excerpt from the March 23 farmdocdaily article posted by University of Illinois Weed Scientist Aaron Hager.

Steps for Successful Weed Management in Dicamba-Resistant Soybean

Step 1
  • plant dicamba soybean seed into a weed-free seedbed
  • achieve a weed-free seedbed through the use of preplant tillage, an effective burndown herbicide(s), or a combination of tillage and burndown herbicides
Step 2:
  • select and apply within 7 days of planting a soil-residual herbicide that targets your most problematic weed species; if desired (and labeled), add dicamba and an appropriate buffer
  • for waterhemp or Palmer amaranth, select a product containing the active ingredients from one of the following categories of control:
Excellent Good Acceptable
sulfentrazone pyroxasulfone     S-metolachlor/metolachlor
flumioxazin metribuzin acetochlor
fomesafen+metolachlor     dimethenamid pendimethalin
  • Excellent: greatest efficacy on Amaranthus species and longest residual control
  • Good: good efficacy on Amaranthus species, residual control generally not as long
  • Acceptable: stronger on grass species but with some activity on Amaranthus species
Step 3:
  • scout fields 14 days after planting, apply dicamba at 0.5 lb ae/acre when weeds are less than 3 inches tall and when conditions allow for the application, consider adding an approved soil-residual herbicide to the tank mix
Step 4:
  • scout treated fields 7 days after the dicamba application; if control is not complete or another flush of weeds has emerged, consider using non-dicamba options for complete control; examples include alternative herbicides, cultivation, and hand rogueing; the goal should be zero weed seed production

University of Illinois Weed Science Field Research Tour

The Extension weed scientists on the University of Illinois campus in Urbana-Champaign have scheduled their annual field day. The Weed Science tour is set for Wednesday June 29th says Aaron Hager.

It’ll be at the South Farms and will begin roughly between 7:30 and 8:00 o’clock in the morning. It will be very similar in terms of format to what we’ve done before. We’ll all gather around the South Farms at the Seed House for a few introductory remarks and comments, and then everybody will get back into their vehicles and we’ll car pool across Windsor Road and look at some of the research plots on the Animal Sciences tracts.

Again, the 2016 University of Illinois Weed Science Field Day is Wednesday, June 29th at the University of Illinois Crop Sciences Research and Education Center, the South Farms, located just to the east of the State Farm Center (Assembly Hall).

Coffee and refreshments will be available under the shade trees near the Seed House beginning at 8:00 a.m. Cost for the Urbana weed science field tour is $10. The event will conclude around noon with a catered lunch.

The tour will provide ample opportunity to look at research plots and interact with weed science faculty, staff, and graduate students. Participants can compare their favorite corn and soybean herbicide programs to other commercial programs and get an early look at a few new products that soon will be on the market.

Marestail Control Prior to Planting

link to article online

Farmers in Illinois, other states too, are struggling to control glyphosate resistant weeds. Marestail can be one of the most challenging under no-till conditions prior to planting soybeans. More often than not farmers are using a tank mix of glyphosate and 2,4-D (two-four-dee). Sometimes the problem is that the weed is already too big to control, at others says University of Illinois Extension Weed Scientist Aaron Hager is its just that the 2,4-D isn’t doing the job any better than the glyphosate.

Quote Summary - Well, there are some alternatives that can be used for control of mares tail in a burn down scenario. A product called Sharpen could be included with glyphosate/2,4-D to try to increase the efficacy on the marestail and if that is the case be sure to include a methylated seed oil with any application that has Sharpen with it. Or alternatively you could switch completely over to something like a glufosinate product, like a Liberty or Interline containing product or something like Gramoxone. Either of those will typically perform better when used in combination with metribuzin and probably 2,4-D in the tank as well.

Tillage is another option, however, Hager says to delay it until field conditions are suitable and be sure to till deep enough to completely uproot all existing vegetation.

4 Step Weed Control Plan for Corn or Soybeans

Since the 1960’s farmers have been using herbicides to control weeds. Frankly, herbicide formulations haven’t changed that much and the weeds have managed to find ways to adapt. Todd Gleason has this four step plan from the Univesity of Illinois to control them in corn or soybeans.

Some weeds have become resistant to the herbicides farmers use to control them. Others have lengthened their germination period, emerging later in the season, avoiding early spring control methods. University of Illinois Extension Weed Scientist Aaron Hager has a four step plan farmers can use to maintain a competitive edge in corn or soybeans. It starts by planting into a weed free seedbed.

Quote Summary - It is easy to achieve a weed free seedbed by either replant tillage, burndown herbicide or a combination of those two. Given the challenges of weather and of resistant populations it is advisable not to plant into existing weed populations or any green vegetation without adequate control ahead of time.

Step two in the plan is to select an appropriate residual herbicide. Be sure it provides very good control of the most problematic weed species in a given field. Pay attention to the label, says Hager, and always apply the recommended rate for the spectrum of weeds in the field.

> Quote Summary - The third step is to make timely post emergence applications. Base those on just not the number of calendar days after planting, but rather base those post decision on adequate scouting. So, return to the fields about two weeks after crop emergence. Scout the fields and determine the weed size, crop development stage and make the decision on a timely application of a post herbicide.

The final and fourth step is to go back to the field seven to ten days later and evaluate how well the post emergence herbicide application worked. It may be that another germination of a weed species warrants a second application. This won’t be know without a return trip.

If we fail to go back and look at how well the product performed, or the level of crop injury we see soon after that application, we could have some very significant challenges later in the growing season.

The days of set-it-and-forget weed control have ended. Todays farmers must scout fields for competitive weeds before during and after the growing season.

Four Step Weed Control Plan for 2016

Farmers battling herbicide resistant weeds are running out of control options. University of Illinois Extension Weed Scientist Aaron Hager has this four step recommendation. You may read detailed information of his four step weed control plan online.