Fresh Manure Can Lead To E. Coli Contamination In Food Gardens
Friday, May 30, 1997
FORT COLLINS--Vegetables and fruit gardeners may want to
learn more about new strains of E. coli bacteria found in cattle
before adding fresh manure to their soil.
Colorado State University Cooperative Extension
horticulturist Carl Wilson said, "Although not all manure carries
these new strains of the deadly bacteria, without extensive lab
testing there is no way to tell if manure is contaminated."
Wilson noted, however, it still is safe to use aged manure
for ornamental and turf plants, since the bacteria would not be
transmitted by eating the plant. He also recommends amending
vegetable gardens with plant-based compost and sphagnum peat.
Well-composted manure may be used because the composting process
eliminates the bacterial problem.
Authorities recently traced a Maine child's death to E. coli
0157:H7 from calf manure his mother added to the family garden.
The bacteria contaminated freshly harvested vegetables that were
poorly washed before eating. Exposed adults generally become ill
and recover, but the organism can be life threatening to
children, the elderly and other immunocompromised individuals.
"Safe food-handling practices are more important now than
ever," Wilson said. "Because lettuce is succulent and difficult
to wash, it appears to be a particularly good host for the
bacteria. But scrubbing and peeling carrots and other vegetables
before use will considerably reduce the risk of bacterial
contamination."
Wilson recommends home gardeners compost all manure before
adding it to the soil. Bacteria will survive winter freezing, so
fall garden applications and even "aged manure" provide no
guaranty of an E. coli-free vegetable or fruit garden. The heat
produced through proper composting kills most pathogens. To be
effective, the compost should heat to 130 to 140 degrees F for
five days or more. Wilson points out, however, that research
reveals two to 10 percent of the pathogens survive the heating
process.
That's why it's important to follow the hot-compost phase
with a "curing" period of two to four months. This will allow
beneficial microbes to wipe out disease pathogens and produce an
acceptable organic soil amendment.
"It's important to note that compost made exclusively from
plant wastes does not need a curing period," Wilson said. "Adding
leaves and other plant materials directly to the garden is safe."
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