Posts tagged ‘marestail control’

Tips and Suggestions for Controlling Marestail this Fall

The following is condensed from the October 6, 2009 OSU CORN newsletter written by Dr. Mark Loux on marestail control.

The goal of a marestail management program is to ensure that the combination of fall and spring burndown and residual herbicides results in a weed-free seedbed at the time of soybean emergence, and little to no emergence of marestail between soybean emergence and crop canopy closure. Even the most effective marestail management programs can fail to completely achieve this, but they often keep the populations low enough in the soybeans that they are not problematic.

Marestail plants that emerge in late summer or fall are easily controlled with a fall herbicide treatment. However, it’s essential to realize that a fall herbicide treatment is not likely to accomplish everything that’s needed in an effective marestail management program.

In those marestail-infested fields requiring a fall herbicide treatment for management of other winter annual annual weeds or dandelion, it is essential not to apply all of the residual herbicide in the fall. This also applies to those fields that are typically so wet that soybeans cannot be planted until mid to late May. In this situation, the goal of a fall residual herbicide treatment might be just to ensure that marestail are not too large when burndown herbicides are finally applied in May. Regardless of the type of herbicides applied in fall, an effective rate of a residual herbicide should still be applied in the spring, to maximize control of marestail that emerges in May and June. We suggest one of the following approaches [for marestail control]:

1. Apply a combination of glyphosate and 2,4-D in the fall, followed by application of residual herbicide in the spring prior to soybean emergence. At the time of soybean planting, the field is likely to be infested with marestail that emerged earlier in spring, so include effective burndown herbicides (2,4-D, Gramoxone, glyphosate, or Ignite or some combination as appropriate based on herbicide resistance, plant size and time until soybean planting) to control emerged plants.

2. Apply 2,4-D with Canopy DF or EX at fairly low rates (e.g. 1 oz of EX or 2 oz of DF) in the fall, followed by application of residual herbicide in the spring (with burndown herbicides if the residual from fall does not hold marestail through planting). It is possible to follow the fall Canopy application with a spring application of a chlorimuron-containing herbicide, as long as the total does not exceed the maximum labeled rate of chlorimuron for the soil type.

3. In ALS-resistant populations where Canopy will fail to provide any residual control of marestail, it may be possible to substitute a combination of 2,4-D with metribuzin in the fall. This combination should control most emerged winter annuals, but can be weak on dandelion. Follow with application of residual herbicide in the spring (with burndown herbicides if the residual from fall does not hold marestail through planting).

Full podcast here:


October 21, 2009 at 1:00 pm

Marestail Control in Soybeans

This article is devoted to one of the most problematic weeds in soybeans: marestail. Marestail is an upright growing plant and can reach 4 feet if not mowed or controlled. Marestail begins as a basal rosette similar to other winter annuals. Following the rosette stage, Marestail expereinces a stage of rapid vertical growth refered to as ‘bolting’. The leaves are 3 – 4 inches in length, and have widely toothed margings. And the stem of marestail is simple and unbranched, and covered with hair.

In a recent fall weed-scouting project, I noted marestail in nearly 20% of the soybean fields in Van Wert County. For those who are battling this weed already, you know that marestail is difficult to control. Marestail is diffiuclt to control for many reasons. First, marestail has the ability to germinate throughout the year. In fact, marestail is typically classified as both a winter annual and a summer annual because it can germinate in the fall and throughout the summer. Next, marestail is tolerant and in some cases resistant to glyphosate. So an application of glyphosate may have little to no effect on marestail. Last, marestail is a prolific seed producer. Weed scientists have reported seed production up to 200,000 seeds per marestail plant. Yes, that’s per single plant. The seeds are small (typically 2mm) and are dispersed easily by wind and equipment.

In OSU research, the most effective control of marestail in soybeans has occurred from a combination of 2,4-D ester, residual herbicides and either glyphosate or paraquat applied in April, when the marestail is still in the rosette stage or has only an inch or two of stem elongation. But even with this ‘loaded’ herbicide package, expect a few marestail escapes. If marestail populations are heavy, OSU researchers recommend delaying the herbicide application until very late-April or early-May to catch as many emerged marestail plants as possible.

Below is the full podcast on marestail.

November 5, 2008 at 7:00 am


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