Experimental investigations of the effects of air pollutants on aphids on coniferous trees

The relative growth, rates of two aphid species feeding on Sitka spruce (Picea sitchensis) and one species on Scots pine (Pinus sylvestris) were measured on two year old trees prefumigated with either ozone (O₃ or nitrogen dioxide (NO₂) and compared with the growth rates of aphids grown, on trees which were exposed to filtered air. All three species showed increased growth rates on trees which were prefumigated with 100ppb NO₂ for periods in excess of 24 hours. However the effects of prefumigation with O₃ were more complex. Only on species,Cinara pilicornis, responded to this treatment and there was a strong interaction between the fumigation treatment and the temperature experienced by the plants during fumigation.