Field Crop News and Notes Mike
Rankin Keeping Glyphosate Effective Glyphosate, the active ingredient in Roundup herbicide, has been widely used in crop production systems since the mid-1970’s. However, the chemical’s popularity has reached new heights since the inception of glyphosate resistant crops (especially soybeans). The concern is obvious: the repeated use of the same chemical herbicide on the same field to control the same weeds will soon lead to herbicide resistant weed biotypes. It’s not a question that it might happen as it already has in other countries and states. The temptation to use glyphosate even more regularly will occur with the further development of Roundup Ready corn hybrids and the introduction of alfalfa and wheat varieties. With this in mind, Chris Boerboom, UW-Extension Weed Management Specialist, suggests the following stewardship practices: • Rotate between Roundup Ready and conventional crops or crops with other types of herbicide resistance. Use Roundup Ready crops in your rotation where they have the greatest economic and management value. • Rotate glyphosate with other herbicide modes of action. Rotate non-glyphosate herbicides over time as well. • Apply glyphosate at labeled rates at the correct stage of growth. • If glyphosate is used as a burndown treatment and post-emergence, tank mix one of the glyphosate applications with another mode of action. • Use cultivation after post-emerge applications of glyphosate when possible. • Scout fields regularly and identify weeds present. • Respond quickly to changes in weed population.
New Oat Variety for 2004 The latest new oat variety out of the Wisconsin breeding program is called Drumlin. It’s described by Wisconsin Certified Seeds as a mid-late maturity oat that heads slightly later than Gem, but several days earlier than Belle. In 20 statewide trials during the past three years, Drumlin has had a higher average yield than all other named varieties tested (123 bushels per acre). At the Arlington Research Center this year, Drumlin yielded a whopping 188 bushels per acre. It has good resistance to crown rust and tolerance to Barley Yellow Dwarf Virus.
Transgenic Hybrids Continue to Yield Above Average in UW Trials According to Joe Lauer, UW-Extension Corn Agronomist, a recent trend in the UW Corn Performance trials is the lower frequency of normal dent corn hybrids yielding above the trial average. From 1973 to 1996, normal dent corn hybrids as a group were distributed around the trial average in a 50:50 ratio, in other words 50 percent of the normal dent corn hybrids were above the trial average and 50 percent of the hybrids were below the trial average. Beginning in 1997 and continuing through 2003, the frequency with which normal dent corn hybrids yield above the trial average has been decreasing. In 2003 only 40% of the normal dent corn hybrids yielded above the trial average. There are still quite a few normal dent corn hybrids that have excellent performance and are the top hybrids in a trial, but greater care must be used when selecting normal hybrids. There are at least two possible reasons that might explain this observation. First, the Bt trait is being incorporated into the best genetics available. Normal dent corn hybrids are being replaced by hybrids with the Bt trait. For the first time more transgenic hybrids were entered into the UW Performance trials than normal hybrids. About 53 to 59% of these hybrids perform above the trial average. Another possible reason for greater than expected performance of Bt hybrids is that low undetected European Corn Borer pressure may exist in the trials and is reducing the performance of normal dent corn hybrids. It is important that the industry maintain a strong genetic base of normal dent corn hybrids because these will always be needed to plant the 20 percent corn refuge area required by EPA when growing a transgenic hybrid.
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