Agronomy Blog

Fall Herbicide Applications

by Brian Weihmeir | Nov 3, 2017

Harvest is in full swing or finishing up for much of the Midwest. It is a busy time of year for growers in the field to wrap up 2017. Often we get caught up in the moment and forget that the 2018 growing season starts in the fall. With the increase in herbicide resistant weed species, weed control is a growing concern each season. An herbicide application in the fall is a great way to stay ahead of the game and control winter annual weeds that emerge during and after harvest.

Brian-Chickweed-1 citedThe application of herbicides in the fall can be very beneficial to growers across the Midwest. With the increasing practice of reduced or no till farming, there is an increase in winter annual weed species such as chickweed, henbit, and shepherd’s purse. Marestail is another weed that can follow a winter or summer annual lifecycle and cause issues. Fields with a history of marestail can benefit from a fall herbicide due to resistance issues. Warmer weather and late rains can cause these winter annuals to become worse than normal years. Brian-Chickweed-2 cited

Typically the best time to apply a fall burndown is from mid-October through mid-November. Herbicides can be applied after this time, but weeds are less susceptible to herbicides after a hard freeze. A typical burndown mix in the fall is a combination of glyphosate with 2, 4-D and/or Dicamba. This will allow control of emerged weeds early and put less pressure on spring burndown applications and make them more effective. A debated topic is whether to include a residual herbicide in the mix. A lot of this decision is dependent on the weather. A residual in the fall can keep a field clean until planting season, but in the event of a harsh cold winter, a residual can last too long and injure the next crop. Also in the event of a mild winter, the residual can break down quickly and allow winter annuals to emerge early spring. For these reasons, it is typically recommended to not outguess Mother Nature and to save your money on residual herbicides for in-season.

Weed control is by far the most important part of a fall burndown application, but growers sometimes forget about some of the tangible benefits that come along with it. The first one is your soil conditions. Having a clean field in the spring with lower weed pressure will warm up the soil faster with less trash on the surface allowing even emergence and higher yields. Another benefit is less insect pressure. Fields with heavy weed pressure will attract insects like black cutworm moths to lay eggs in the spring and cause problems for the upcoming crop. Henbit can also be a host for soybean cyst nematodes. The other benefit is giving you flexibility with your spring burndown application. As we all know spring can be a narrow window to get all our field work done. With a fall burndown, we can buy ourselves a little more time to target smaller weeds in the spring with our preplant applications.

Fall herbicide applications are a great way to get a head start on a successful 2018. When making your applications, make sure to always follow the label and practice good environmental stewardship. For local recommendations and suggestions, feel free to contact your local LG Seeds Agronomist. Have a safe and successful harvest!

Sources and Additional Information:

  1. https://ag.purdue.edu/btny/weedscience/documents/startingnextyearnow.pdf
  2. https://ag.purdue.edu/btny/weedscience/documents/burndownmadness.pdf
  3. http://bulletin.ipm.illinois.edu/?p=3750
  4. https://crops.extension.iastate.edu/cropnews/2017/10/fall-marestail-horseweed-management
Note: The information in this issue is based upon field observations and third party information. Since variations in local conditions may affect the information and suggestions contained in this issue, LG Seeds disclaims legal responsibility therefore. Always read and follow label instructions.

LG Seeds and design are trademarks of SCA Limagrain.

Download a copy of this Technical Bulletin: Tech_356 - Fall Herbicide Applications