Weed of the Week: Giant Foxtail
Giant foxtail is a common summer annual grass in row crops and forages. It emerges for a long period in the spring. It typically begins emerging after the beginning of ragweed and lambsquarters emergence. Seeds emerge from shallow soil (1 inch or less) and plants produce between 500-1500 seeds.
Herbicides should be applied to small giant foxtail plants. Rotary hoeing can be effective on foxtail if performed when the seedlings are very young, under 1/4 inch tall. Other mechanical tactics like night tillage and flaming have not been found to be very effective on it. Fields with a lot of giant foxtail may be rotated to alfalfa for two years in order to deplete its weed seed bank. It does not grow well in alfalfa, and by the time the field is rotated back to corn or soybeans, most foxtail seeds will be depleted. While adjusting planting date and tillage timing are methods that help manage some weeds, the long germination period for giant foxtail (which extends well into the growing season) makes this technique ineffective on it.
In pastures, infestations should be addressed immediately while they are small, because large infestations may require long-term treatment and pasture renovation. A long-term treatment regimen includes soil testing, fertilization, working the ground, and reseeding with a competitive grass and clover mix, then monitoring the pasture and spot treating any small populations that emerge. More information on foxtail control in pastures can be found below in the resource titled “Foxtail Control in Pastures and Hayground.”
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Locations of resistant populations:
Illinois, Iowa, Maryland, Minnesota, Pennsylvania (Search by State to see which resistant populations are present in each state)