Several factors have contributed to delayed applications and marestail escapes this spring. Includes recommendations for timely postemergence control in corn and soybean.
One of the challenges with spring burndown application is timing. Wet and windy conditions can delay spraying and under these conditions weeds can grow significantly in a few days. Waiting until planting to spray troublesome weeds such as marestail may be too late to achieve adequate control. In addition, waiting until soybean planting limits the available herbicide options since there are relatively few labeled effective burndown chemicals for spraying at this time. The following section identifies key treatment aspects to consider for several resistant varieties in Nebraska.
Figure 1. No-till cereal rye cover crop planted on October 21, 2016 after corn harvest in North Platte. Cereal rye was drilled at 60 lb per acre on 7.5-inch row spacing. Photo taken April 10, 2017.
Fall-planted cereal rye is increasingly used as a cover crop in corn and soybean cropping systems in Nebraska. The authors address control of cereal rye through herbicide and mechanical measures and include a USDA NRCS map of recommended termination deadlines.
Figure 1. The benefit of a residual herbicide can be clearly seen in these photos of fields with and without residual six weeks after planting. (Photos by Rodrigo Werle)
Are last year's weed escapes still haunting you? Applying these six key management practices and five key timings can help you improve control of herbicide-resistant weeds this year.
Figure 1. (Top left) Newly emerged horseweed seedlings in the cotyledon stage. (Bottom left) Seedling in the rosette stage with true leaves formed. (Right) Horseweed plants that are early in the bolting stage.
Horseweed (marestail, Conyza canadensis L.) is a unique weed species that can emerge in both fall and spring. In Nebraska, unlike the eastern Corn Belt, horseweed populations predominantly emerge in fall as a winter annual.
Cover crops can provide either ecosystem services or forage benefits but understanding how they fit in cropping systems is still limited. This study assessed the effects of planting date (early and late), plant population (low, average, and high) and corn maturity (80 to 115 days relative maturity) on corn yield.
Figure 1. Marestail seedling growing in a no-till field. Due to its small size in the fall, pay special attention during scouting, especially in no-till fields where residue can hide seedlings.
With corn and soybean harvest nearing completion in Nebraska this is a great time to begin scouting fields for winter annual weeds like marestail. Timing is critical to successful control of marestail, especially in no-till soybeans as many populations have evolved resistance to glyphosate and ALS-inhibiting herbicides.
