Bushland, Texas
August 25, 2004
Dr. Mustafa Mirik, assistant
research scientist with Texas Agricultural Experiment Station,
and a team of collaborators, are looking at plant damage and
stress in wheat. Their current work deals with damage caused by
aphids. In the future, the team plans to include other stress
factors, such as drought and disease.
Using remote sensing technology, Mirik and his team employed
hyperspectral and multispectral equipment to help assess insect
damage from greater distances. Field scouting alone does not
yield such extensive information.
For example, they took multispectral images ranging from near
ultraviolet through most the visible light spectrum. The more
sensitive hyperspectral equipment also allows the scientists to
see much higher wave lengths than visible light.
Dr. Jerry Michels, Experiment Station entomologist and program
leader at Bushland said if the observations are sensitive
enough, the scope of the damage can be determined accurately.
The goal is to help a farmer pinpoint where treatment
applications need to go.
"If this work is successful, farmers may be able to save some
money and help the environment," Michels said.
Images were taken by both devices before the researchers went
into a field. Then the aphids were counted. They gathered data
from all sources for comparison and evaluation.
Mirik used both hand-held and aircraft-mounted equipment in the
study. The more sensitive hyperspectral unit can be used closeup
or remotely but is more expensive. The multispectral equipment
was hand-held only.
Research by others has dealt with establishing crop
characteristics, such as green canopy health and cover.
"However, to our knowledge, a limited number of those studies
were focused on spectral measurement of aphid-damaged wheat in
controlled environments at the leaf-level only," Mirik said.
"Little attention was dedicated to aphid feeding damage at
canopy levels in field conditions," he said. "This became the
focus our research."
The researchers counted insect densities for greenbug and
Russian wheat aphids. They gathered needed information in and
above stressed and unaffected wheat plots in Texas, Oklahoma and
Colorado. Data was generated from the hyperspectral ground
spectrometer and a digital camera above the aphid-infested and
non-infested wheat. Insect density was measured in quarter
square meter ratios for each sample.
"Sometimes at least 30 tillers were cut at ground level and
taken to the laboratory where aphids were counted for each
plot," Mirik said. Plot sampling was intensive.
Tillers that remained in the plot also were counted so complete
estimates of aphid density were possible. At other times,
technicians counted all aphids within plots during the early
growing season or clipped all plants and counted aphids in the
laboratory during the late growing season.
Comparisons were made in healthy and stressed wheat under all
conditions. Early results show promise for remote measurement of
aphid-induced stress to estimate density and separate injured
from healthy wheat.
Future work will collect image data for aphid infestation of
agricultural crops not only in field conditions but in
controlled environments, Mirik said.
"We will take this research into at least three levels of
stress–water, nutrient and aphid in wheat and sorghum in the
future. Our goal is developing and validating a spectral aphid
stress index for major agricultural crops." |