Influence of water availability on use of spectral vegetation indices for detection of European corn borer infestation in Nebraska corn plots

In 2007 corn grown for grain was planted on approximately 35 million ha in the United States and had a production value of more than $52 billion dollars. Transgenic corn expressing the plant incorporated protectant Bacillus thuringiensis toxin represented nearly 50% of the 2007 planted corn and is expected to increase in 2008. Development of insect pest resistance to Bacillus thuringiensis toxin threatens the long term sustainability of this crop and monitoring to detect insect resistance as early as possible is considered an important management component. Spectral vegetation indices derived from high spectral resolution airborne hyperspectral imagery may provide a reliable means of detecting plant stress in corn fields related to insect feeding damage. However, little is known about how water availability to corn plants affects the use of spectral vegetation indices to discriminate insect related plant stress. During the 2004 and 2005 growing season in Nebraska, we selected spectral vegetation indices that emphasize foliar plant pigments and evaluated their ability to detect dryland and irrigated experimental plots of corn manually inoculated with Ostrinia nubilalis (Hübner) neonate larvae. Our findings show that although spectral vegetation indices were successful in identifying O. nubilalis infestation in both irrigated and dryland corn plots, water availability did impact our ability to discriminate insect related feeding damage. Results from this experiment, implications and future directions will be discussed.