Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/14/2004
Publication Date: 8/15/2005
Citation: Riedell, W.E., Osborne, S.L., Hesler, L.S. 2005. Insect pest and disease detection using remote sensing techniques. Meeting Proceedings. 7th International Conference on Precision Agriculture, July 25-28, 2004, Minneapolis, MN. Interpretive Summary: Cereal crop productivity in the US Great Plains is often reduced by aphid infestations [Russian wheat aphid (RWA) and greenbugs (GB)] and aphid-vectored disease [barley yellow dwarf (BYD)]. Yield losses of 35 to 60% have been reported for small grains damaged by GB or RWA. Producers often apply insecticides to manage cereal aphid populations and reduce subsequent yield losses. Barley yellow dwarf virus (BYDV) is transmitted to cereal plants by aphids. Plants damaged by BYDV can show up to 70 % less yield when compared to uninfected plants. Crop canopy chlorosis and necrosis in small grain fields infested with greenbugs or Russian wheat aphids could be used as a diagnostic tool by farmers to detect crop damage from cereal aphid population outbreaks. If information on the exact field location of aphid outbreaks was available, farmers could target insecticide applications specifically to pest-infested portions of the field. Remote sensing of BYD could be a useful tool for providing data on the disease epidemiology over large geographic areas, measuring the extent of crop damage for insurance purposes, or as a selection tool to improve breeding efficiency for resistant small grains. The objectives of this 2-yr field study were to characterize canopy reflectance spectra of oats damaged by GB, RWA, or BYDV, and to determine if changes in reflectance spectra were related to leaf area index, canopy temperature, tissue chlorophyll levels, and yield. Our observations support and extend those of others who found that crop stresses that result in leaf chlorosis, mottling, necrosis, or leaf temperature changes can also have profound effects upon crop canopy reflectance spectra. However, in our experiment, the pattern of the spectral responses attributed to aphid feeding or disease damage may have been attenuated by drought stress.
Technical Abstract: Cereal crop productivity is often reduced by aphid infestations and aphid-vectored disease. Knowledge of how different insect species and plant disease affect small grain crop canopy reflectance may allow the use of remote sensing techniques to detect specific insect pests and to distinguish between insect and disease damage. The objectives of this 2-yr field study were to characterize canopy reflectance spectra of oats (Avena sativa L.) damaged by greenbugs (GB; Schizaphis graminum Rondani), Russian wheat aphids (RWA; Diuraphis noxia Kurdjumov), and aphid-vectored viral disease (BYD; barley yellow dwarf), and to determine if changes in reflectance spectra were related to canopy temperature, tissue chlorophyll levels, and leaf area index. Oat plants contained in 1-meter-square cages were infested with aphids or infected with barley yellow dwarf virus (BYDV) at the 3-leaf stage. Aphid populations were removed from each cage after a total infestation of 300 aphid-days per tiller (about 10 to 15 days after infestation). For the BYDV treatment, plants were infected with viruliferous bird cherry oat aphids (Rhopalosiphum padi L.) for a period of 72 hours. Canopy temperature, chlorophyll, leaf area index, and canopy reflectance (350 to 1100 nm) were measured at the flag leaf development stage. Grain yield was measured at crop maturity. In both years of the study, leaf chlorophyll concentrations were less and canopy reflectance in the 600- to 650-nm range was greater (compared with control) in oat canopies infected with BYDV. In the second year of the study, canopy temperature was greater while canopy reflectance in the near infrared (750- to 900-nm) range was less in oat canopies that were infested with RWA or infected with BYDV. Stepwise regression analysis on reflectance data revealed multiple regression equations useful for predicting canopy temperature, chlorophyll, and yield in the second year of the study but not in first. These results suggest that canopy characteristics and spectral reflectance differences between insect infestation damage and disease infection damage can be measured in oat crop canopies but that these differences may not be consistent from one growing season to the next.