Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: July 14, 2002
Publication Date: March 30, 2003
Citation: RIEDELL, W.E., OSBORNE, S.L., LANGHAM, M.A., HESLER, L.S. REMOTE SENSING OF BARLEY YELLOW DWARF AND WHEAT STREAK MOSAIC DISEASE IN WINTER WHEAT CANOPIES. INTERNATIONAL CONFERENCE ON PRECISION AGRICULTURE ABSTRACTS & PROCEEDINGS. 2003. v. 6. p. 160-166. Interpretive Summary: Barley yellow dwarf (BYD) and wheat streak mosaic (WSM) are serious viral diseases of winter wheat in the Great Plains. The BYD virus is transmitted to cereal plants by aphids. As the name implies, plants damaged by BYD are stunted and chlorotic when compared to uninfected plants. Other symptoms of BYD include red leaf discoloration, leaf necrosis, reduced root growth, delayed heading, and yield losses up to 70 percent. The WSM virus is transmitted by leaf curl mites. Symptoms of WSM include stunting, leaf mosaic, and yellow leaf streaking. Yield losses of up to 70 % have been recorded in wheat infected with WSM virus. It may be possible to use remote sensing of BYD- and WSM-damaged wheat canopies to detect crop damage caused by these diseases. Remote sensing of BYD and WSM 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, and as a selection tool to improve breeding efficiency for resistant winter wheat. Our objective was to characterize canopy spectral reflectance of winter wheat damaged by BYD or WSM. Our data suggest that the spectral responses seen in winter wheat canopies were much less dramatic in BYD treatments than in WSM treatments. One of the important physiological effects that BYD has upon wheat is a dramatic reduction in root length and depth of rooting. Plant damage and yield loss to BYD generally are much less pronounced in wet years. Yield loss to BYD generally ranges from 50 to 70 %. The level of yield loss observed in the two years of the current experiment (25 % reduction in 1999; 15 % reduction in 2000) never approached this reported range. Thus, the small differences in spectral characteristics, canopy characteristics, and grain yield for plants infected with BYD virus in comparison to uninfected plants in 2000 are likely explained by the amelioration of BYD damage due to much higher than normal rainfall in May of 2000. It is interesting to note that the above normal precipitation in April of 1999 did not result in the same level of amelioration of BYD symptoms and yield loss as seen in 2000. The canopy spectral responses and yield loss seen in WSM treatments were very consistent across both years of the study. However, the reflectance sensitivity graphs presented in the present study have that same general appearance as those seen for wheat plants damaged by cereal aphids. We conclude that BYD and WSM viral diseases cause changes in spectral reflectance in wheat canopies, but that viral disease stress-causing agents do not cause spectrally unique canopy reflective responses. Additionally, growing season environment may interact with crop growth and viral disease symptom expression to confound attempts to use remote sensing to easily detect these crop diseases under field conditions.
Technical Abstract: The efficiency of field monitoring for barley yellow dwarf (BYD) and wheat streak mosaic (WSM) viral diseases would be improved with knowledge of reflected solar radiation from winter wheat crop canopies. Our objective was to characterize canopy spectral reflectance as well as other canopy and yield characteristics of winter wheat infected with BYD or WSM virus. A 2 year field experiment was conducted at Brookings SD. Winter wheat plants in the second leaf stage were infected with BYD or WSM. Control plants received no virus infections. Leaf area index, canopy temperature, and canopy reflectance sensitivity (350 to 1100 nm) were measured at the flag leaf development stage. Grain yield and yield components were measured at crop maturity. Reflectance sensitivity analysis for BYD infected treatments revealed dramatically different responses, likely due to spring soil moisture, across the two years of the experiment. In 1999, sensitivity analysis revealed a sharp peak near 460 nm and a broad peak at around 600 nm with shoulders at 580 nm and 630 nm. Leaf area index and yield were about 25 % lower than control in 1999. Sensitivity analysis results, leaf area index, and canopy temperature were very similar to control in 2000. Yield was reduced by about 15 % by BYD in 2000. WSM-damaged winter wheat crop canopies had very similar responses over both years of the experiment. Sensitivity analysis revealed sharp peaks at 450 to 460 nm and at 630 to 640 nm as well as a broad peak at 580 nm. WSM virus infection had very little effect on leaf area index in both years of the experiment. Canopy temperature, however, was about 10 % higher than control in 2000. Yield loss to WSM was about 50 % in 1999 and 70 % in 2000. We conclude that BYD and WSM viral diseases cause changes in spectral reflectance in wheat canopies, but that viral disease stress-causing agents do not cause spectrally unique canopy reflective responses. Additionally, growing season environment may interact with crop growth and viral disease symptom expression to confound attempts to use remote sensing to easily detect these crop diseases under field conditions.