Sycamore aphid numbers and population density. III. The role of aphid induced changes in plant quality.
Leaf age of sycamore, Acer pseudoplatanus, had a marked effect on the performance of the aphid, Drepanosiphum platanoidis. Aphids reared on young leaves grew at significantly greater rates, had shorter development times and achieved greater adult weights than those reared on older leaves. Leaf infestation history had no significant effect on aphid performance. Aphid infestation at bud-burst had a marked effect on the host-plant, reducing the area of the leaves to less than half the area of leaves on uninfested trees. Analysis of the foliar free amino-acid compositions indicated that no major changes in leaf quality occur as a result of prolonged aphid infestation. These results are discussed in the context of current theories of the role of induced changes in plant quality on herbivore populations, with specific reference to the population dynamics of the sycamore aphid.