Relationship between SO2 dose and growth of the pea aphid, Acyrthosiphon pisum, on peas.

A series of experiments was carried out in controlled environment cabinets to investigate the effects of SO(2) dose on the mean relative growth rate (MRGR) of pea aphids, Acyrthosiphon pisum, feeding on the pea plant, Pisum sativum. There was a significant linear increase in the MRGR of aphids feeding on SO(2)-fumigated plants, relative to control aphids feeding on plants in charcoal-filtered air. The increase in MRGR reached a maximum of 11% at SO(2) concentrations between 90 and 110 nl litre(-1). MRGR declined at higher SO(2) concentrations until above 220 nl litre(-1) it was below that of the controls. The dose-response curve is discussed in relation to reported changes in the nitrogen metabolism of plants subject to air pollution, the response of aphids to host plant nitrogen and possible toxic effects of high concentrations of SO(2) on the aphid.