Compost, Mulch and Microbes May Protect
March 31, 1999
DAVIS, Calif., March 31--A
special compost, a plastic mulch and beneficial microorganisms may be
ingredients for the perfect recipe to protect tomorrow's strawberry fields from
weeds and soil-borne diseases, Deputy Agriculture Secretary Richard Rominger
said last night at an anniversary celebration for the
University of California's
Scientists with USDA's Agricultural
Research Service in Salinas, Calif., are testing the strategy's potential as a
replacement for some uses of methyl bromide. This chemical fumigant is being
phased out in the U.S. because it is thought to deplete Earth's protective
"The experiments in California are part of USDA's nationwide search for
reliable, affordable substitutes for methyl bromide," said Rominger in
remarks to an agriculture workshop on the
Protection Act. "Strawberry growers are major users of the chemical
and have relied on it for decades to keep plants free of pathogensthe
microorganisms that can cause crop disease."
fumigate their fields with a mixture of methyl bromide and chloropicrin before
planting. That fumigation kills soil-dwelling pathogens, such as those that
cause verticillium wilt in strawberries. It also kills weed seeds.
ARS plant pathologist Carolee T. Bull
is leading tests of a compost that is enhanced with enzymes, organic acids and
beneficial bacteria. The compost is combined with corn gluten meal and
beneficial fungi. She is doing the work at commercial strawberry fields and
research plots in central California.
"The enzymes," said Bull, "should speed decomposition of the
compost, making nutrients available to beneficial microbes that we have applied
to the fields.
"The beneficial bacteria that we are investigating may stimulate the
plants' defenses against pathogens," she continued. "The fungi--known
as mycorrhizae--help plants take up water and phosphorus from the soil."
The experiments will also determine whether weeds are quelled by beneficial
microbes and corn gluten meal, a corn processing byproduct.
In strawberry test plots, Bull and colleagues will compare size and health
of plants grown using the new strategy to plants fumigated with either methyl
bromide or methyl bromide plus chloropicrin.
The tests are part of a cooperative research and development agreement
between ARS and Soil Technology, Fallbrook, Calif.
The average American eats about five pounds of strawberries per year.
Strawberries are fat-free, low in calories and a source of vitamin C, folic
acid, potassium and fiber. The fruit also is high in antioxidants that may
protect cells from damage.
California is this country's top strawberry producer. The nation's 1998
strawberry crop of 869,350 tons was worth more than $1 billion to growers.
Other ARS efforts to find methyl bromide alternatives include:
- In Kearneysville,
W.Va., testing natural plant extracts like benzaldehyde as soil fumigants and
postharvest fumigants on produce
- In Weslaco, Texas, protecting
grapefruit from Mexican fruit fly and green mold, Penicillium digitatum,
with refrigerated storage in ultra-low oxygen chambers
S.C., breeding bell peppers like Charleston Belle, and Carolina Wonder that
naturally resist the southern root-knot nematode Meloidogyne incognita,
reducing the need for methyl bromide as a soil fumigant.
Scientific contact: Carolee T. Bull, ARS Crop Improvement and
Protection Research Unit, Salinas, Calif., phone (831) 755-2889, fax (831)