Be on the lookout for a new weed problem. Woolley cupgrass is here and probably isn't going to go home. Several characteristics make woolly cupgrass difficult to manage. The seeds germinate over a wide range of temperatures so woolly cupgrass can germinate early in the spring with additional flushes occurring throughout the season. The large seeds germinate from up to four inches deep and produce large, vigorous seedlings. Also, the seedlings are more tolerant to several soil applied herbicides than giant foxtail, which has made control difficult. Uncontrolled plants are prolific seed producers. Single woolly cupgrass plants can produce over 150,000 seeds. Once established in a field, seed dormancy will ensure that infestations will continue into the future. Chris Boerboom, UW Extension Weed Specialist , offers these woolly cupgrass management strategies.
Prevention:
Fields where woolly cupgrass is most easily controlled are fields where it was never introduced. Because woolly cupgrass is probably spread by contaminated field equipment, till and harvest infested fields last to prevent moving seed to noninfested fields. After tilling, chopping silage, or combining in infested fields, thoroughly clean the equipment. If small new patches are found in a previously clean field, use aggressive control measure to try to prevent its establishment and spread.
Crop competition:
Woolly cupgrass begins growth early in the season and is very aggressive. Thus, it is important to plant competitive crops and manage them favorably so they maintain as much of a competitive advantage over woolly cupgrass as possible. Plant corn and soybeans soon after the final seedbed tillage so the crop has an even start against cupgrass. A delay in planting give the advantage to this vigorous weed. Crop rotation is also an important tool. Alfalfa is competitive against woolly cupgrass and its frequent harvest prevents cupgrass seed production. After a few years of alfalfa, the seed bank of woolly cupgrass should be significantly reduced, but not eliminated. Winter wheat also is a very competitive rotational crop against cupgrass.
Mechanical control:
Rotary hoeing kills a large percentage of the first flush of woolly cupgrass if properly timed. Rotary hoe about seven to ten days after the last tillage for seedbed preparation when cupgrass seedling have sprouted, but before they emerge. If a postemergence herbicide program is planned for cupgrass control, rotary hoeing gives greater flexibility for the timing of postemergence herbicide application. In row crops, cultivation is low cost, highly effective, and substantially improves woolly cupgrass control. This option should be considered when cupgrass emerges after soil-applied herbicides have lost their activity or after application of nonresidual postemergence herbicides.
Chemical control:
Several corn and soybean herbicides initially suppress or control woolly cupgrass. Early season woolly cupgrass control may appear to be excellent, but diminishing control with time usually results in heavily infested fields at harvest. Residual herbicides do not persist at the high concentrations required for season long control and postemergence herbicides lack residual control.
No single herbicide is a consistent, stand alone program. Woolly cupgrass control is variable from year to year. Research trials have provided very erratic results. A treatment that appears quite effective in one year may fail miserably the next season for no apparent reason. Grower experience from year to year also supports this observation. Research results suggest that woolly cupgrass control with particular herbicides is very dependent on appropriate environmental conditions. The most consistent woolly cupgrass control is obtained when several management tools are used in combination. Light infestations can be controlled either with a soil-applied herbicide and cultivation or a postemergence herbicide and cultivation. Moderate and heavy infestations will require more effort. The first step for a heavily infested field may be rotation to alfalfa or a combination of a residual plus post emergence herbicides (as sequential or tank mix treatments) in corn or soybeans.
For more information contact Mike Rankin|
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