Acyrthosiphon pisum was given a choice between pea plants supplied with four N levels. When whole plants were exposed, the settling response and subsequent reproduction of alighted aphids increased, as the level of N supply increased, with the exception of the highest N supply. However, the density of settled alatae (in terms of number per unit leaf area) increased as the level of N supply decreased. In a free-choice experiment, leaf discs from different N treatments were exposed to alatae for 24h. The settling response was affected by leaf colour, with the greatest number on yellow discs. Relationships between N supply, soluble nitrogen and chlorophyll concentration, and aphid abundance or density were established.

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