The effect of simulated acid rain on performance of the aphid Euceraphis betulae (Koch) on silver birch

The effect of artificial acid rain on the reproduction and survival of the aphid Euceraphis betulae on silver birch was studied in Turku, southern Finland. Eight bioassays were done during 1984-1986. In four of the bioassays the aphids produced 40% to over 100% more progeny on birches watered with dilute sulphuric acid (pH 3.5) than on control trees. In four other cases the performance of aphids did not differ between the treatments. An index of aphid reproduction pooled over the whole study was significantly higher on acid-treated than on control birches. The reproduction of aphids on acid-treated birches was enhanced when precipitation was below long term average, suggesting an interaction between the stress caused by acid treatment and dry periods.