Canyon, Texas
February 4, 2008
When disease and insect problems
in crops are visible to the naked eye, it may be too late to
treat. That’s why Dr. Christian Nansen,
Texas AgriLife Research
entomologist, likes to take a closer look.
A hyperspectral look, that is.
Nansen, small grains entomologist at the Texas AgriLife Research
and Extension Center at Lubbock, uses a hyperspectral camera to
determine how light is being reflected off plant leaf surfaces.
He discussed the technology at the High Plains Vegetable
Conference in Canyon.
“Just like when we start having the flu, our body responds and
we get a fever,” he said. “The fever is because our body is
mobilizing its immune system. When a plant undergoes stress
caused by diseases, insects or the environment (like drought),
it will cause changes in its metabolism and that leads to subtle
changes in the way it reflects light.
“We can use this camera to detect stress at an earlier stage
than by visual inspection.”
For instance, Nansen said, root rot is all underground, and
generally plants are half dead when the damage becomes visible.
“But if you could see it earlier, you may have time to treat for
the fungus causing the problem,” he said.
The hyperspectral camera detects diseases in any plant, Nansen
said. And with insect damage, the key parameter to control is
early detection.
“When scouting for spider mite infestation, you have to take a
lot of samples to see mites when the infestation level is low,”
he said. “But with spectral imaging, you can see it earlier and
it is less intrusive.”
The technology is similar to that of remote sensing, Nansen
said. However, instead of putting the camera in an airplane, it
is placed just over the canopy of a crop, perhaps mounted on a
four-wheeled all-terrain vehicle or on the center-pivot
irrigation system.
He said his research team is in the early stages of testing the
technology. They are starting by collecting spectral profiles of
healthy and sick plants and developing classification
algorithms.
“We are using it now to do early detection of zebra chip in
potatoes and cotton root rot, and also looking at spider mite
stress on corn plants,” Nansen said. “We’re developing
technology that we hope can work with other programs.”
Currently, potato producers must use visual symptoms of stress
in the plants to detect zebra chip, a disease that has no
treatment, and determine if a field should be harvested, he
said.
“We want to see if we can detect the disease in the actual
fields while plants are still growing,” Nansen said.
“With a potato plant, a lot of inputs and resources are needed.
If we can detect an infestation early, our technology may help
producers decide whether it is worthwhile to spend more
resources on a given field and/or whether their potatoes should
be sold for chipping or another market.”
He said because it has not been determined what causes the
actual infection, he hopes to be able to use the hyperspectral
process to determine when it starts to occur and what is
happening with the plant at that time.
“We think we can also obtain a much higher accuracy using the
reflectance technology to scan the potatoes and see how it will
be after frying,” Nansen said.
The zebra chip effect causes the potato to turn brown after
frying, he said. At this time is doesn’t appear to affect
quality and does not show up in baking potato, but the
discoloration after frying is a problem for the chipping
industry.
Another possibility, he said, is to utilize the technology in
plant breeding to determine genetic differences in germplasm.
Seed analysis is already being done much the same when
scientists look for protein content in wheat, oil content in
peanuts or maturation of tomatoes.
“We have a wealth of information on reflectance technology
available,” Nansen said. “But there are certain characteristics
about what we do that are unique.
“We’re trying to make it relevant on a larger scale without
being too expensive,” he said. “I think if we can develop some
robust classification algorithms, we can do many things and
automate the system if it can pass over the field.”
The technology is ripe for someone to put a complete package or
system together, Nansen said, because the different computer
programs have been written and could be combined into a single
program with the proper funding.
by Kay Ledbetter |
|