Air pollution increases Aphis fabae pest potential

Abstract

Many observations have been made of increased population densities of herbivorous insects in areas subject to air pollution^1–3. However, in the absence of experimental investigations, the significance of most of these observations is not clear and any underlying causal mechanisms remain obscure. The only published studies designed to investigate experimentally the impact of pollutants on plant–herbivore systems involve fumigations with either hydrogen fluoride (HF)⁴ or sulphur dioxide (SO₂)^5,6 of Phaseolus vulgaris and Glycine max plants, infested with the Mexican bean beetle, Epilachna varivestis: in general the results showed that HF reduced beetle performance whereas SO₂ stimulated it, but the relative importance of direct and indirect effects of the pollutants was not elucidated. We show here stimulatory effects of SO₂ and NO₂ and ambient London air on the growth of the black bean aphid, Aphis fabae, and demonstrate that these have been mediated entirely via the host plant.