Texas: Resistant Pigweed – Steps To Take To Gain Control

    Many area producers now view weed control, glyphosate-resistant pigweeds to be specific, as our number one IPM problem for the area. Unfortunately, there has been no silver-bullet development this offseason, and no one-shot cure for the weed dilemma. I would like to quote Dr. Peter Dotray about the issue:

    “While glyphosate resistance is a big problem, it is one that we have an answer for. We can, with the technology we have available today, make effective sprays and achieve control of glyphosate resistant pigweed and other troublesome weeds.”

    The renewed idea and use of pre-plant residual, rotation, mode of action alteration, and in-season residual are all common in the area’s agricultural lexicon again. There might not be any-thing groundbreaking or “new” this season for our weed control battle and the release of some much anticipated technology is still at least a year out.

    For this season, most of us have discussed the systems approach to weed control and our recommendations until producers can re-cite them verbatim. And still, we have weed problems and expect more. There are two main points that I would like to drive home to producers today on the subject.

    The first is residual incorporation. Regardless of what systems approach to weed control we choose, it has been proven by experiment and experience that poorly incorporated pre-plant herbicides lose levels of effectiveness if incorporated poorly or late. Producers must become knowledgeable with whichever residual path chosen, and make certain these herbicides are optimally incorporated. This does not necessarily mandate conventional tillage for all fields.


    Photo: ©2014 Debra L. Ferguson

    But if we are utilizing tillage for incorporation, we need to make certain the herbicide is fully incorporated into the top two inches of the soil, the area where most weed seeds germinate. Likewise, in no-till scenarios, we must apply enough water to move our residual herbicides into the same two-inch zone.

    The second point I would like to stress is the necessity to control young weeds and not allowing them time to mature. Mature weeds are better prepared to “resist” any herbicide treatment. The majority of weed problems the producers in our program experienced during the 2013 season re-sulted from missing small weeds early. In some cases, a percentage of weeds came through a pre-plant residual herbicide. This was the likely result of an unfamiliar residual herbicide application or poor incorporation, but the environmental conditions and weed pressure faced during

    2013 cannot be ignored. Another factor is the timing of our first over-the-top (OVT) herbicide application in cotton. In the past our first OVT herbicide application could be made to sizeable weeds with good effects. This is no longer the case. I strongly suggest scouting fields for any possible weed germination and catching any emerging weeds as soon as possible.

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