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Weed Management On Prevent Plant Acres (07/03/13)

Issue as described in an email: What are options with 2 million acres of prevent plant in the northern tier of counties with potential for glyphosate resistant kochia.

Weed Management On Prevent Plant Acres

Issue as described in an email: What are options with 2 million acres of prevent plant in the northern tier of counties with potential for glyphosate resistant kochia. Many fields have not been worked or burn-down herbicide treatments were not applied. What weed concerns (such as winter annuals) will growers face next year whether they plant a cover crop or not.  If they do plant cover crops and some survive along with winter annuals what course of herbicide treatments are available to them next year? Should they try and control the cover crop this fall prior to the frosts to ensure no weeds next spring.

There are many options that a grower can use for plant management and prevent plant acres. We know from planter skips, drowned out areas, or any place where crops are not growing that bare ground invites new weed flushes. Most weeds have a prolonged germination and even though daylight is shorter, most weeds can germinate with each rain event. The hotter weather creates warmer soils which encourages weed germination.

For growers that use no till as their crop production system, herbicide use to control weeds and undesirable species is about the only option, if cover crops are not used. If any control system has been delayed then weed species are likely tall and will be very difficult to control through herbicide use. This situation will require multiple herbicides, high rates, and the most aggressive adjuvants to kill weed infestations.

There was much interest in 2011 in the use of cover crops. This article is not intended to give the pros and cons of each cover crop but to point out that cover crops can be very useful to inhibit weed flushes by providing groundcover. Cover crops themselves can become a weedy problem which can be present in the next year’s crop if not killed this fall or by winter kill.

Page 23 and 31 in the North Dakota weed control guide gives excellent burn down options. Many of these options have no or little chemical residue to interfere with crop rotation. Some herbicides listed will have chemical residue and only corn or soybeans can be planted. These treatments are designed for full spectrum weed control and they should kill most all weed flushes and other undesirable species. If cover crop residue is not too big than many of the treatments will be effective in killing the cover crop this fall.

Tillage is always an effective tool if weeds have got excessively large and for very high infestations. Tillage can also act to stimulate germination of annual weeds so multiple tillage passes may be needed throughout the remainder of the growing season to control weeds. The goal for this season would be to provide groundcover to suppress weed germination but also to avoid weeds or cover crops as a problem in next year’s crop.

Rich Zollinger

Extension Weed Specialist

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