Indirect effects of air pollutants: Changes in plant/parasite interactions

The impact of air pollutants on plant/parasite-interactions has been investigated. It could be demonstrated that fumigation of Vicia faba L. with 0·15 ppm SO 2 (400 μg m −3) or 0·2 ppm NO 2 (400 μg m −3) during 7 days caused changes in plant metabolism which resulted in higher growth rates of the aphid Aphis fabae Scop. feeding on these plants. Fumigation of V. faba with 0·085 ppm O 3 during 2 or 3 days, however, caused decreased aphid growth on fumigated plants. That result could be reversed by higher O 3 concentrations or through the presence of NO x during O 3 fumigation. Ambient air comprising a mixture of pollutant gases had a strong enhancing effect on aphid performance. Thus, the growth of A. fabae on field bean plants was significantly higher in ambient summertime. London air than in charcoal-filtered air. Similarly, the growth of Macrosiphon rosae L. on rose bushes ( Rosa sp., cv. Nina Weibull) was improved in ambient summertime Munich air; the increase in growth rate averaged about 20%.