Fort Dodge Messenger, IA
07-28-07
Researchers detect some diseases from satellites
By KRISTIN DANLEY-GREINER, Messenger staff writer
With Asian soybean rust a real threat in the U.S., Iowa State University
researchers have found a way to use satellite images as a detection tool for this
costly disease.
Forrest Nutter, a plant pathology professor at ISU, worked last year on a
collaborative research project picking up traces of Asian rust in crops located in
South Africa. By using positioning system and geographical information system
technologies, scientists are able to pinpoint diseases like Asian rust down to a
square meter area.
Dr. David Wright with the Iowa Soybean Association said that satellite imagery is
a “very important tool" in helping to determine the plant health of a given
production area.
“Healthy plants appear one way on satellite imagery, stressed plants look entirely
different," Wright said. “You can even identify different stresses based on
wavelength of light returned to the satellite. The challenge becomes evident
when the plant is infected with multiple diseases. It is too early to determine how
effective this technology might be in helping to identify an early infection of a
devastating disease like soybean rust. This disease appears first on the lower
canopy often hidden by healthy-appearing vegetative tissue above."
Currently, satellite imagery is considered to be the “next generation" for
diagnosing problems in fields,” Wright said.
“Today it is very costly, but that cost will decline with time," he said. “A manager
can use this technology today to estimate yield reduction from wet spots and
highly stressed areas. Determining yield loss from subtle stress is much more
difficult."
Still, satellite imagery cannot replace scouting in the fields.
“Aerial imagery cannot replace hands-on diagnosis," Wright said. “Many
diseases, like soybean rust, must be managed early, thus they must be identified
very early."
Producers should be keeping an eye out right now for the western bean cutworm,
which “will not go away," according to Marlin Rice, ISU Extension
entomologist. The northwest quarter of Iowa has been hit the hardest by the
western bean cutworm since it took up residence in Iowa in 2000. Rice noted that
ISU has detected the pest’s presence in nearly all of the state’s 99 counties.
Some believe that the theory of pest replacement is what has driven up western
bean cutworm populations. As European corn borer populations have dropped
courtesy of in-plant traits, the western bean cutworm has taken its place.
“I’ve got a theory. I don’t know how good it is yet, but I have to ask myself why
western bean cutworm became a pest of Iowa in 2000,’’ Rice said in a statement.
‘‘We know it was in the state for the previous 30 years, but it was rare.”
‘‘What has changed during the years prior to 2000 that would affect these
insects, in my mind, is transgenic corn, which decreased European corn borer
populations and allowed western bean cutworm, which is not affected by
YieldGard Corn Borer, to expand. I have some data that supports that, but I’d
hate to say that’s the singular reason. We know the insect is affected by disease,
and maybe diseases aren’t as severe here as in other states," he said.