Fungal Risk Assessment Helps Clear Trade
Hurdles By Jan
December 26, 2000
WASHINGTON, Dec. 26Dwarf bunt fungus concerns in
milling wheat exports that threatened foreign trade have been addressed by a
pest risk assessment (PRA) system developed by U.S. Department of Agriculture and industry
Such concerns surfaced in spring 1999, when U.S. trade officials
presented a 57-page PRA report during negotiations with China to ease
restrictions on U.S. wheat imports. The negotiations centered around
Chinas concern that accepting such grain could spread the fungus to their
domestic wheat crops.
The fungus, Tilletia controversa Kuhn (TCK), sporadically
infects winter wheat crops in the Pacific Northwest, but poses no human health
risk. Under certain conditions, it damages the wheat kernel.
With the pest risk assessments, our trade negotiators were
able to present compelling scientific evidence showing TCK poses a negligible
risk to Chinas domestic wheat crop from U.S. grain imports,
Agricultural Research Service
administrator Floyd Horn said today. The PRAs have also proved invaluable
in similar negotiations with India, Brazil and Mexico in 1998.
As part of the agreement signed with the United States on April
10, 1999, China eased its zero-tolerance policy to a threshold level of 30,000
TCK spores per 50 grams of grain. According to USDA estimates, that opened the
door to $150 million worth of possible U.S. wheat exports.
The PRAs draw on more than 10 years of laboratory and field
research on TCKs genetic variability, geographic distribution, spore
growth, virulence and survival under various crop-production practices and
grain handling regimens.
In 1997, this led to the creation of the TCK Task Force by Wilda
H. Martinez, who assembled a network of collaborators at various USDA agencies,
the U.S. wheat industry, Chinese scientific and regulatory entities, and
international wheat pathogen experts. Martinez is ARS
North Atlantic Area
A key element of the teams PRA research involves using
various computer models, including the geophytopathological model,
or GPM for short. With it, researchers can identify climatic regions around the
globe favorable to the funguss survival. When applied to China, for
example, the GPM showed that regions conducive to the fungus were few as well
as far from Chinas import grain terminals and mills.
When applied to Brazil and Mexico, the model showed a lack of
conditions necessary for the fungus to thrive--45 days of uninterrupted
moisture, temperatures of -2 to 10 degrees Celsius, and mild winters under
continuous snow cover.
Martinez said the priority now is conducting research to
develop a pest risk assessment on another wheat disease pathogen, Tilletia
indica or Karnal bunt fungus. Discovered in the southwestern United
States in 1996, Karnal bunt fungus is currently on the quarantine lists of 72
An article about TCK research appears in the December issue of
Agricultural Research magazine, and on the
Contact: Wilda H. Martinez, Director, ARS
North Atlantic Area,
Wyndmoor, Pa., phone (215) 233-6593, fax (215) 233-6719,