Remote Sensing for Detection of Cotton Aphid– (Homoptera: Aphididae) and Spider Mite– (Acari: Tetranychidae) Infested Cotton in the San Joaquin Valley

Abstract We explored remote sensing methods for their potential to distinguish aphid- (Aphis gossypii Glover) and spider mite–infested (Tetranychus spp.) cotton (Gossypium hirsutum L.) from uninfested cotton. Field plots were established using selective and disruptive pesticides to establish a range of aphid and mite populations over 2 yr. Aerial and satellite remote sensing data in 2003 and 2004 were supplemented with ground-based remote sensing data in 2004 and by ground-truthing of arthropod populations in both years. Mite- and aphid-infested cotton was detected using aerial data in the green and near-infrared (NIR) wavelengths in 2003, with subeconomic threshold aphid population levels. At the time aerial data were collected, mite populations peaked at 95% leaves infested and exceeded treatment threshold levels of 30–50% leaves infested. However, the number of mites per leaf in the treatments was low to moderate (32, 9, 4, 6, and 2 average mites/leaf). Moreover, cotton infested with cotton aphids above economic threshold levels was consistently detected using NIR wavelengths from the satellite data in 2004. Similarly, aphid-infested cotton was detected at both sub- and supraeconomic threshold aphid levels using NIR wavelengths from the ground-based remote sensing data. Finally, accumulated mite-days were linearly correlated with a canopy, false color, and a vegetation index using satellite data in 2004. Wavelengths in the NIR were fair to moderately accurate predictors of aphid- and mite-infested cotton.