title: Soybean Aphid (Hemiptera: Aphididae) Affects Soybean Spectral Reflectance.
abstract: Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is the most economically important insect pest of soybean in the north central United States. Scouting-based integrated pest management (IPM) programs could become more efficient and more widely adopted by using plant spectral reflectance to estimate soybean aphid injury. Our objective was to determine whether plant spectral reflectance is affected by soybean aphid feeding. Field trials were conducted in 2013 and 2014 using caged plots. Early-, late-, and noninfested treatments were established to create a gradient of soybean aphid pressure. Whole-plant soybean aphid densities were recorded weekly. Measurements of plant spectral reflectance occurred on two sample dates per year. Simple linear regression models were used to test the effect of cumulative aphid-days (CAD) on plant spectral reflectance at 680 nm (RED) and 800 nm (NIR), normalized difference vegetation index (NDVI), and relative chlorophyll content. Data indicated that CAD had no effect on canopy-level RED reflectance, but CAD decreased canopy-level NIR reflectance and NDVI. Canopy- and leaf-level measurements typically indicated similar plant spectral response to increasing CAD. CAD generally had no effect on relative chlorophyll content. The present study provides the first documentation that remote sensing holds potential for detecting changes in plant spectral reflectance induced by soybean aphid. The use of plant spectral reflectance in soybean aphid management may assist future IPM programs to reduce sampling costs and prevent prophylactic insecticide sprays.
authors.affiliation: Department of Entomology, University of Minnesota, 1980 Folwell Ave., Saint Paul, MN 55108. alves011@umn.edu.
authors.forename: Tavvs M
authors.initials: TM
authors.lastname: Alves
authors.affiliation: Department of Entomology, University of Minnesota, Northwest Research and Outreach Center, 2900 University Ave., Crookston, MN 56716.
authors.forename: Ian V
authors.initials: IV
authors.lastname: Macrae
authors.affiliation: Department of Entomology, University of Minnesota, 1980 Folwell Ave., Saint Paul, MN 55108.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Koch
mesh_terms: D000818:Animals; D001042:Aphids; D002734:Chlorophyll / Q000032:analysis; D060434:Herbivory; D011158:Population Growth; D013025:Glycine max / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D002734:Chlorophyll
keywords: Aphis glycines; Glycine max; cumulative aphid-days; reflectance; remote sensing