Ames, Iowa
November 11, 2004
The U.S. Department of Agriculture (USDA) confirmed
yesterday that Asian Soybean Rust has been found in
Louisiana, the first known incidence of the disease in North
America.
Asian soybean rust is an aggressive fungal disease that can
reduce soybean yield substantially, said Greg Tylka,
Iowa State University plant
pathologist. The disease has the potential to cause
extensive damage to plants and can travel quickly through
infected areas depending on environmental conditions.
Tylka said many scientists expect soybean rust to show up in
Iowa during next year's growing season. He also said two
variables will influence how soybean rust may affect Iowa's
soybean crop in 2005; when the disease arrives and what the
weather conditions are at the time it arrives.
"It's difficult to guess if soybean rust will be here in
early July or late August, but if we're lucky it will be
late August," Tylka said. "The weather conditions will be
another concern. In 2004, we had perfect weather for rust,
lots of moisture and moderate temperatures. If we have a
hot, dry year soybean rust will be much less of a concern."
The soybean rust fungus probably will not overwinter in Iowa
or other northern soybean-growing areas, Tylka said. In
order to infect Iowa fields, the spores would have to be
carried up from the southern United States by winds every
year.
X.B. Yang,
Iowa State plant pathologist, has studied soybean rust since
1989 and uses weather models and maps to track wind
movements to predict where rust spores may be carried. He is
one of the leading experts in the world and is a member of a
USDA soybean rust detection assessment team. The team is
examining fields today in Louisiana.
Prior to
yesterday's announcement, the Iowa Department of Agriculture
and Land Stewardship applied and received Section 18
emergency use permits from the EPA to allow producers to
apply certain fungicides to manage soybean rust. The permits
became effective with the USDA announcement yesterday. Tylka
said he wants to put the arrival of the disease in the
proper perspective and not have producers overreact and
purchase fungicides unnecessarily.
"We should be ready to react quickly, but we need to be
careful not to overreact," Tylka said. "If we identify
soybean rust in Iowa, there still may be times during next
year's growing season when it wouldn't make economic sense
to spray."
Bob Wisner, Iowa State agricultural economist, said the
additional costs associated with the management of soybean
rust could influence spring planting.
"Farmers may shift some acres from soybean to corn because
of expenses and the uncertainty of soybean yield prospects.
I would not expect a major shift but there could be a modest
shift," Wisner said.
The discovery doesn't impact the 2004 crop and came at an
opportune time to prepare for next year, Wisner said.
"If there were a good time for soybean rust to enter the
United States, that time would be now," Wisner said. "The
fact that it was discovered after harvest allows time to
prepare for the next growing season and that's a plus."
Tylka coordinated training sessions last summer for more
than 400 certified crop consultants, certified professional
agronomists and independent crop consultants as first
detectors in a "fast track" reporting system. The fast track
system was developed to speed up reporting of soybean rust.
The system is simple: producers submit samples to first
detectors at no cost. First detectors send suspect samples
to triage personnel, who are Iowa State Extension field
staff, for more diagnosis. The triage person then forwards
suspect samples to the Iowa State University Plant Disease
Clinic.
The fast track system is part of an overall action plan
prepared by the Iowa Soybean Rust Team to quickly identify
soybean rust and efficiently manage samples submitted to the
Iowa State Plant Disease Clinic. The team has worked for the
past two years preparing to respond to the introduction of
Asian soybean rust into the United States and Iowa.
Team
members represent Iowa State University, the Iowa Department
of Agriculture and Land Stewardship, the Iowa Soybean
Association/Iowa Soybean Promotion Board and the United
States Department of Agriculture Animal and Plant Health
Inspection Service. More information about the team and its
action plan are available at
http://www.soybeanrust.info.
Asian soybean rust was first recorded in Japan in 1902. The
pathogen moved throughout Asia, Australia and Africa before
it was discovered in South America in 2000. Asian soybean
rust has been moving northward through South America and was
recently reported north of the equator.
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