|Elliott, Norman - Norm|
Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/28/2005
Publication Date: 3/15/2006
Citation: Mirik, M., Michels, G.J., Kassymzhanova-Mirik, S., Elliott, N.C., Catana, V., Jones, D.B., Bowling, R. 2006. Using digital image analysis and spectral reflectance data to quantify damage by greenbug (Hemitera: Aphididae) in winter wheat. Computers and Electronics in Agriculture. 51:86-98. Interpretive Summary: Remote sensing is a tool that could help farmers evaluate whether their crop should be treated with insecticide to control pest insect infestations. The idea behind the use of remote sensing for pest insect infestation detection is that when infestations of the pest insect cause injury to the crop, the injured plants will reflect solar radiation differently than healthy plants. The effect of plant stress on light reflectance has been documented for various types of stress, such a drought and nutrient deficiency, but has not been sufficiently studied for pest insects. We studied the usefulness spectral reflectance of solar radiation to quantify damage caused by the greenbug, Schizaphis graminum. The greenbug is an aphid, which is a severe pest of wheat. Statistical analysis showed that there were very strong associations between the level of injury to wheat plants caused by greenbugs and reflectance of light in certain wavelength bands in the visible and infrared portions of the electromagnetic spectrum. The results suggest that remote sensing using remote sensing can be nondestructive, rapid, cost-effective, and reproducible technique to determine greenbug injury to wheat. With more research it may be possible to develop remote sensing as a cheap and effective tool for evaluating fields over broad areas to determine if insecticide treatment is required to control greenbug infestations in them.
Technical Abstract: The usefulness of digital image analysis and spectral reflectance data to quantify greenbug damage (Schizaphis graminum Rondani) was evaluated for two winter wheat (Triticum aestivum L.) fields, three field experiments, and one greenhouse setting in Oklahoma and Texas. A hyperspectral field spectrometer and a digital camera were used to record reflectance and to acquire images over 0.25 m2, 0.37 m2, and 1 m2 greenbug-damaged wheat canopies. A large number of spectral vegetation indices compiled from the literature were calculated and their relations with greenbug damage were investigated. The mean percentage greenbug damage estimated through digital image analysis varied from 13 ± 1/0.25 m2 to 73 ± 7/0.37 m2. The mean greenbug density ranged from 191 ± 22/0.25 m2 to 54,209 ± 7,908/0.37 m2. Correlation analyses showed that there were very strong associations between greenbug damage in wheat and spectral vegetation indices. Correlation coefficient ranged from 0.82 to -0.98. Thus, these results suggest that remote sensing using spectral reflectance and digital images can be nondestructive, rapid, cost-effective, and reproducible techniques to determine greenbug damage in wheat with repeated accuracy and precision. Together with the existing spectral indices, two versions of a new index algorithm are also suggested in this paper.