An Organic Cure for a Turfgrass Disease?
Dollar spot, seen here on creeping
bentgrass, is one of the two most
troublesome diseases of golf course
|Golf courses in the United States
spend tens of millions of dollars each year on fungicides to control the
turfgrass disease called dollar spot. First appearing as small, unsightly spots
of dead grass, the diseased areas eventually merge and cover large areas. The
cause of dollar spot is a fungus called Sclerotinia homoeocarpa.
Chemical fungicides for dollar spot may someday be replaced by an organic
inoculation consisting of beneficial soil microorganisms as the first choice,
thanks to University of Missouri-Columbia (MU) student Matthew T. Wood, who
became interested in ARS microbiologist
Robert J. Kremer's experiments on biological weed control. Kremer discovered
that the highest numbers of weed-suppressing microbes in fields were found
where crops were rotated, chemicals and tillage were minimal, and organic
materials, like compost, were added.
While an undergraduate, Wood and his adviser, MU turfgrass researcher Eric H.
Ervin, envisioned that soil could be managed to maintain a healthy mix of
microbes that would suppress growth of the dollar spot pathogen. If so,
suburban lawnkeepers and golf course managers could reduce the input of
pesticides into the environment.
Close-up of dollar spot damage
on Kentucky bluegrass.
|Wood received a $1,000
stipend from the MU College of Agriculture, Food, and Natural Resources
(CAFNR), to work with Kremer and Ervin, studying the biocontrol of S.
homoeocarpa. The CAFNR On-Campus Research Internship provides opportunities
for aspiring undergraduate students to gain firsthand experience in a
research project under the mentoring of a researcher.
"Our research project showed that a multiculture of compatible anaerobic
and aerobic microorganisms slowed development of dollar spot on creeping
bentgrass in the greenhouse," says Kremer. The success may pique interest
in further research on ways to reproduce a similar lasting beneficial effect in
soils already teeming with microflora.
In theory, says Kremer, if microbes in the mixed cultures coexist with native
soil microorganisms, applying the mixture to soil might ensure establishment of
cultures that would enhance the beneficial effects of biological processes,
including growth suppression of fungal pathogens.
Such cultures have been named "effective microorganisms," or EM, by
Teruo Higa, professor of horticulture at the University of the Ryukyus,
Okinawa, Japan. Higa's studies also inspired Wood's experiments.
For laboratory and greenhouse studies, the researchers locally obtained an EM
liquid culture of bacteria, yeasts, and algae. Wood then grew the mixture of
microbes on horse manure, brewery waste, wheat bran, and charcoal to make a
material known in Japan as bokashi. He grew S. homoeocarpa on
heat-sterilized millet seeds to produce an inoculum used to infect 4-week-old
bentgrass seedlings growing on sand mixtures with and without bokashi
In the greenhouse experiments, 8 weeks after bentgrass seeding,
Sclerotinia had infected less than 1 percent of the turf in the pots
that contained six parts sand to four parts EM-bokashi. But in the control
pots, containing only sand (90 percent) and peat (10 percent), 19 percent of
the turf became infected.
As principles of microbial effects on disease and weed suppression are learned,
says Kremer, the potential for increasing the production and use of EM organic
amendments may be realized. Recyclable materials to support EM growth are
abundant. Ultimate benefits may include more efficient use of manure, food
wastes, sawdust, and woodchips.By
Agricultural Research Service Information Staff.
This research is part of Soil Resource Management (#202) and Crop Protection
and Quarantine (#304), two ARS National Programs described on the World Wide
Web at http://www.nps.ars.usda.gov.
Robert J. Kremer is in
the USDA-ARS Cropping
System and Water Quality Research Unit, University of Missouri,
Natural Resources Building, Room 302, Columbia, MO 65211; phone (573)
882-6408, fax (573) 884-5070.
"An Organic Cure for a Turfgrass Disease?"
was published in the August 2001
issue of Agricultural Research magazine.