The performance of apterous pea aphids (Acyrthosiphon pisum) was assessed on host plants (Pisum sativum) supplied with four nitrate-N levels (0, 3, 15 and 30 mM) using various growth, development and reproductive parameters in controlled environmental conditions. The results indicated that aphids reared on plants supplied with N-free nutrient solution consistently had a longer pre-reproductive period, shorter reproductive period, shorter post-reproductive period, and shorter lifespan (longevity) than the aphids reared on N-fertilised plants. However, the differences in reproductive periods, post-reproductive periods or longevities of aphids between the 0 mM N treatment and the highest N level (30 mM) were not significant. Aphid performance, particularly in terms of adult weight, total fecundity, reproductive rate and intrinsic rate of increase (r m) increased as N supply was increased up to 15 mM, and then declined with the highest N level (30 mM). Similar trends between treatments were confirmed by measuring the mean relative growth rate (MRGR) of aphids, although statistically only the aphid MRGR on N-deficient plants (0 mM) differed significantly from the other N treatments. The relationships between several measures of aphid performance, in particular the r m/MRGR relationship, were examined across N treatments and were discussed.

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