Fall Control of Weeds

Weeds are always a pain no matter what time of the year it is. To help control weeds ahead of time, fall applications can save you time when the push to seed comes about in the spring. This in turn allows for your crops to get the upper hand on the weeds in the spring especially if it is too wet to get in the field before the seeder does seeing as we have very unpredictable weather like we did this year. Fall applications also work to control the winter annual weeds such as foxtail, bluegrass, groundsel and chickweed because they germinate in the fall to be established before the snow making them the first things up in your field come spring. It also helps to control perennials such as Canada thistle and dandelion because in the fall these plants prepare for winter by taking all the nutrients, along with the chemical, and push it down into the roots of the plant which eventually kills it. Getting rid of these weeds in the fall can also increase how quickly your soils warm up because a bare field will be absorbing more heat and warming up faster than a field covered in weeds that absorb that heat instead this in turn allows for seeding to happen faster.

Some options for fall weed control along with what they control and how are:

Edge is a granular herbicide that is great to use because it is a group 3 instead of growers using a lot of group 1 or 2 herbicides it switches up the herbicide rotation a bit to get away from resistant issues. Edge helps to work against resistant weeds such as group 2 resistant kochia. This is a great chemical to use ahead of seeding canola because it controls multiple grassy and broadleaf weeds as well as giving a long term control of weeds that show up in flushes. This chemical is best added with a valmar and harrowing system.

Avadex is also a granular herbicide in group 8 which does a good job on controlling wild oats that seem to spread like wild fire. Especially since wild oats are starting to develop resistance to group 1 and group 2 herbicides. When avadex is applied in the fall it does not need to be worked into the soil unless there is a large amount of straw which if this is the case just a light harrowing helps to shake the avadex granules to the soil surface. This can be used in fields that cereals and canola will be seeded into to control weeds such as wild oats, yellow and green foxtail, as well as supress wild buckwheat, Russian thistle, redroot pigweed, lamb’s quarters, and kochia.

PrePass XC has a great fall control of weeds such as narrow leaved hawks beard, dandelion, flixweed, and foxtail barley. This chemical hangs around in the soil for a 21 day period to give an extended control of weeds that germinate in the fall to get a jump on the spring weeds. After combining, heavy harrowing is good to get the weeds to germinate and grow before spraying with prepass, as the plant needs to be at least 60% green. Spraying when the plant is small allows for the spray to work effectively because the plant won’t have enough sugars stored up for the winter yet. Warm weather (15° or more) is good a few days after because it allows the herbicide to move through the plant better.

For more information on these fall applied chemicals and others, talk to the staff at Cavalier Agrow at any location.

http://www.potatogrower.com/2014/08/fall-burndown-benefits-beyond-weed; The Potato Grower Magazine, Aug 20, 2014

http://agrinews-pubs.com/Content/Default/Illinois-News/Article/Fall-herbicide-applications-may-bring-spring-benefits-/-3/78/11130 ; Nat Williams, Field Editor; Sept 10, 2014

http://www.grainews.ca/2010/09/06/four-reasons-to-consider-soilapplied-herbicides-this-fall-for-sep-6-2010/ ;Gerald Pilger, Four Reasons To Consider Soil-Applied Herbicides This Fall, Sep. 6, 2010

http://beyondagronomy.com/newsletter-archive/September-13-2011 ; steve@beyondagronomy.com , Sept 13, 2014