Nitrogen Fertilization Effects on the Composition of Foliar Amino Acids of Russet Burbank Potato

Colorado potato beetle (CPB) is a notorious defoliating pest of potato crops. The CPB populations are generally suppressed by chemical insecticides. However, the CPB has the capability to rapidly develop resistance to registered chemicals. With the aim of reducing chemical applications to control the CPB, efficient integrated pest management (IPM) has to be implemented. As an herbivorous pest, the CPB lives mainly on potato foliage. Thus, the chemical composition of potato leaves, such as sugars, amino acids and glycoalkaloids, could play an important role in determining the feeding behavior and physiology of CPB. For instance, it has been shown that potato foliar sugars and amino acids promote CPB feeding while glycoalkaloids inhibit CPB development by adversely affecting the central nervous and digestive systems. Here we tested in a greenhouse experiment the effects of different nitrogen (N) fertilization rates (0, 60, 120, 180, and 240 kg N ha−1) on the chemical composition of potato leaves in relation with their potential impact on CPB. We found that N fertilization had no significant effect on leaf glycoalkaloid concentrations. However, the concentration of foliar sugar and amino acid concentrations increased under low N fertilization (0 to 120 kg N ha−1), decreased under 180 kg N ha−1 and re-increased at 240 kg N ha−1. The relatively low sugar and amino acid concentrations observed at 180 kg N ha−1, suggests that this N rate may be effective for CPB management while maintaining a high tuber yield. These findings support the implementation of an IPM strategy to control CPB by identifying management factors inducing changes in leaf chemical composition.