Drought Stress and Nitrogen Fertilization Affect Cereal Aphid Populations in Wheat Fields

Abstract

Water stress and nitrogen deficiency are two constraints that negatively affect growth and productivity of wheat plants. Moreover, the interaction between these two stresses could affect the susceptibility of wheat plants to insect attack. In order to examine the influence of drought stress and nitrogen fertilization on piercing-sucking insect pests, the population abundance of four cereal aphid species; English grain aphid Sitobion avenae, wheat aphid Schizaphis graminum, Bird cherry-oat aphid Rhopalosiphum padi, and corn leaf aphid Rhopalosiphum maidis has been monitored in two water treatments (water stress and well-watered) and two nitrogen levels (120 and 180 kg N ha-1). Results revealed that S. graminum was the most dominant specie in all treatments, followed by S. avenae. The population of all aphids tends to increase in the second half of the season coinciding with the emergence of wheat spikes. Stressed-wheat plants attracted more aphids, especially when water deficit synchronizes with an increase in N fertilization. Aphids vigorously thrive better on stressed plants amended with high nitrogen level. Contrary, the lower infestation rate was observed in well-watered plots with lower nitrogen rate. Plant characteristics, such as days to heading, plant height, and chlorophyll content were significantly decreased in drought-stressed plants, while higher N rates increased such parameters. Grain yield and its components were reduced with drought stress and reduced nitrogen fertilization. The current study advocates avoiding severe drought concurrently with an increasing in nutritional augmentation which it might contribute in an increase in insect pest infestation and decreasing in wheat plant traits.