Posts tagged ‘24D’

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

Fall Ag Weed Control Tips

OSU Extension Weed Specialist, Dr. Mark Loux, put together a great article in the September 21 CORN Newsletter. Below, I have summarized the article:

Fall herbicide treatments can have a range of goals, from control of warm-season perennials prior to crop harvest to control of winter annuals that make for a messy seedbed next spring. Optimum timing can vary based on life cycle, but we can roughly lump the various life cycles into one of two categories:

1) Weeds that must be treated before frost, which pertains to all warm-season perennials, including: johnsongrass, pokeweed, milkweeds and hemp dogbane, and horsenettle. The first frost will cause these weeds to shut down, if they have not already matured and senesced. Herbicides are no longer effective after this occurs.

2) Weeds that should be treated after frost and in some cases even after a hard freeze. Winter annuals, biennials, and cool-season perennials fit into this category, and they are often most effectively controlled when herbicides are applied between mid-October and mid-November. Weeds that fall into this category include: chickweed, purple deadnettle, mustards, cressleaf groundsel, poison hemlock, wild carrot, Canada thistle, quackgrass and dandelion.

In general, mixtures of 2,4-D and glyphosate work well.  One of the most problematic weeds in my area is dandelion.  For dandelion, combinations of 2,4-D and glyphosate are recommended, but combinations of 2,4-D with Basis or Canopy are also among the most effective treatments on dandelion.

Full audio podcast here:

October 1, 2009 at 1:00 pm


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