Bacteria May Turn a Weed into a Weakling
By Ben Hardin
October 29, 1998
Leafy spurge, one of the worst weeds on western ranges, is doing some good
for a change--and doing itself a disservice, scientists hope.
As a lab rat at the Agricultural Research Service, spurge is
helping scientists ferret out which root-dwelling bacteria might have potential
as commercial bioherbicides to thwart this pesky weed and perhaps others. ARS
is the chief scientific research agency in the U.S. Department of Agriculture.
Rhizobacteria live on or within a few millimeters of roots. As roots grow
through the soil oozing juices in their wake, the microbes feed on the
substances. Some of these microbes, called deleterious rhizobacteria (DRB),
also produce toxins. These trigger cells of some plants to produce excessive
hormones. The hormonal flood may keep seeds from germinating or damage plants
by putting their life processes in overdrive.
Weeds weakened by DRB toxins are less able to compete with other plants,
such as field crops and forage plants, for soil nutrients, moisture and
sunlight. Wimpier weeds are also more vulnerable to other controls.
Leafy spurge, a Eurasian native, infests at least 29 states. It costs four
of them--Montana, Wyoming and North and South Dakota--an estimated $144 million
Using half-gram samples of leafy spurge tissue culture, ARS microbiologist
Robert J. Kremer at Columbia, Mo., developed a time- and labor-saving procedure
to screen DRB for further testing on whole plants.
So far, Kremer and colleagues have tested thousands of strains of DRB at the
agencys Cropping System and Water Quality Research Unit. About 30 percent
are highly toxic to leafy spurge. Many have reduced root growth in preliminary
field tests. Some DRB may prove better suited than others for mass production
and commercial use.
This months Agricultural Research magazine contains an article
about the DRB research--and a related story on the agencys special 5-year
anti-spurge project. The stories are also online at:
Scientific contact: Robert J. Kremer, ARS
Cropping System and Water
Quality Research Unit, Columbia, Mo., phone (573) 882-6408, fax (573)