Scentless chamomile, a noxious weed that grows as an annual, winter annual and sometimes as a perennial, is a serious threat to agriculture, especially during years of above-normal precipitation, says Garry Bowes, co-ordinator of the Integrated Noxious Weed Management Program in Saskatoon.
“In a series of experimental plots, the summer annual growth form of scentless chamomile, at a density of 25 weed plants per square metre, reduced the yield of spring wheat by 60 percent in a cool, wet year. In a hot, dry year, the same experiment reduced yield by 15 percent,” said Bowes.
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The winter annual form is even more competitive. At a density of 25 plants per square metre, spring wheat yields were reduced 60 percent in a moderately moist year, and 20 percent in a hot, dry year.
Producers should use the three weaknesses in the life cycle of scentless chamomile to keep it off their property, Bowes said.
“First, scentless chamomile seeds can’t ‘fly.’ Seeds move with water, drifting snow and, most often, human activity. Everyone should make a serious effort not to transport scentless chamomile seed. Producers should also use clean seed, asking for a purity analysis from sellers of forage seed.”
The second scentless chamomile weakness is its showy white flower, which can be easily identified from a distance. Once the plant is spotted, he said, low densities can easily be picked, bagged and burned.
“And the third weakness is the weed’s strong stem. When pulled, the whole plant comes out, reducing the likelihood of leaving plant parts in the soil that can reproduce a new plant.”
Weed biology and identification features, including photographs, are available in leaflets at all Saskatchewan Rural Service Centres and on the Saskatchewan Agriculture internet website at www.agr.gov.sk.ca. Chemical control of scentless chamomile is discussed in the department’s publication Guide to Crop Protection 1999.
