Louisiana weed scientists get first look at chemical effectiveness

One of the benefits weed scientists enjoy is the ability to evaluate various compounds or technologies prior to their commercialization. In addition to potential benefits, they also identify potential pitfalls. These can include crop injury, carryover effects to subsequent crops and effects from off-target applications.

The 2011 research season is a perfect example of newer technology and compound evaluations at the LSU AgCenter Northeast Research Station in St. Joseph, according to LSU AgCenter weed scientist Donnie Miller, who is also research coordinator at the station.

"Research trials are currently under way to evaluate weed management strategies in cotton that has been developed to tolerate over-the-top applications of the herbicides glyphosate and glufosinate in a single application,” Miller said. In addition, evaluations are being made in cotton tolerant to herbicides Dicamba and 2, 4-D.

Research trials initiated at the station focus on newer developments in weed management. They often center on identifying an optimum rate depending on soil type or target weed.

Researchers also are looking at residual herbicides that will suppress weeds in soybean fields and will buy some time before over-the-top applications are needed.  One of the driving forces behind development of these materials is the onset of glyphosate resistance in weed species such as marestail and Palmer amaranth, also known as pigweed.

"Although once a concern in neighboring states, glyphosate resistance documentation in the past few years has brought the issue to the forefront in Louisiana agricultural crop production,” Miller said.

The problem growers are encountering is some weeds have become resistant to glyphosate herbicide, which normally kills a broad-spectrum of weeds. This requires growers to look for ways to stop these weeds before they are resistant to glyphosate.

"One of the primary defense mechanisms for mitigating glyphosate resistance among weed populations is the use of residual soil materials with a different means of controlling the plant, than glyphosate,” Miller said.

A new herbicide compound being evaluated this year for use in soybean is pyroxasulfone.  As highlighted during the Northeast Research Station field day, the compound will be marketed as Zidua by BASF Ag Products.

Miller said this herbicide gives growers some flexibility in their management systems.“Zidua is applied pre-plant, pre-emergent or early post-emergence and requires rain or irrigation water to activate it in the soil.”

The major advantage is if Zidua gets into the weed seed zone, it will give the soybean the needed window of growth opportunity with limited weed competition.  Early results have shown good activity with the compound on a number of problem weeds facing Louisiana soybean producers.

Source: Delta Farm Press