A cover crop of mustard.
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Scientists "Smear" Pests With
Mustard By Jan
October 12, 2004
Got crop pest problems? Spread some mustard on them--the plant,
that is, not the condiment.
Service scientists are growing stands of cultivated mustard and other
Brassica species as a possible alternative to using chemical fumigants to
rid crop fields of nematodes, weed seeds and other soilborne pests.
The mustards' "biofumigant" effect is attributed to
isothiocyanates, chemical byproducts of the plants' decomposition that make the
soil toxic to nearby pests. Indeed, farmers in parts of the United States and
Europe have sought to exploit this phenomenon by preceding their crops with
stands of mustard, rapeseed and other Brassica species.
But there's still much to learn about how these biofumigant
plants control pests, the conditions Brassicas prefer and their
cumulative effects on the soil environment, according to Rick Boydston, an
agronomist in ARS' Vegetable and
Forage Research Unit at Prosser, Wash.
Since 2000, Boydston has led a team of ARS and
Washington State University scientists in
monitoring the mustards' biofumigant effects in greenhouse and field studies.
Eventually, the resulting information could lead to new cropping systems that
use mustards better, or pinpoint their limitations.
For example, scientists are checking the sprouting ability of
redroot pigweed seed that has been dug out from beneath stands of white
mustard, sorghum-sudangrass, winter wheat or an oat-hairy vetch mixture.
Results thus far indicate delayed germination only. In contrast, 99 percent of
the redroot pigweed seeds from fumigated plots didn't germinate at all.
In greenhouse studies, scientists monitored the effects of
crushed seedmeal from brown mustard and field pennycress on potted irises and
three pests: chickweed, prickly lettuce and root-knot nematodes. The irises
suffered no ill effects, but more than half of the weeds failed to sprout, and
nematode numbers fell by 70 to 80 percent.
article describing these and other mustard studies appears in this month's
issue of Agricultural Research magazine.
ARS is the U.S. Department of
Agriculture's chief scientific research agency.