Energy flow in an apple plant-aphid (Aphis pomi De Geer) (Homoptera: Aphididae) ecosystem,with respect to nitrogen fertilization

The effect of nitrogen fertilization on the life table parameters of green apple aphids, feeding on apple saplings of different nutritional quality, was investigated. The experiments were carried out with cloned apple plants (cv. Golden Delicious), all originating from one seed, growing in a climate chamber under constant conditions. The apple saplings were irrigated with nutrient solutions containing different nitrogen levels (0.2, 0.5, 1, and 3 N), and infested with Aphis pomi De Geer. The 1 N treatment corresponded to a 15 mM nitrogen concentration, containing NO₃^- and NH₄⁺ in a 14:1 ratio. The levels of nitrogen fertilization studied here influenced the life table parameters of A. pomi in the following way: the mean generation time of A. pomi, growing on the 0.5 N treatment, was lower than the corresponding values found on the 0.2 and 1 N treatments. The highest net reproduction rate was produced on low (0.2 N) nitrogen nutrition. The intrinsic rate of natural increase was highest on the 0.5 N treatment.