DROUGHT STRESS AND CEREAL APHID PERFORMANCE

The performance of clones of Rhopalosiphum padi and Sitobion avenae fr om England and Spain was examined on drought-stressed tillering winter wheat in an environment chamber at 14 +/- 1 degrees C. Two different levels of drought stress and an unstressed control were established by different watering regimes which resulted in drought-stressed plants being smaller at the end of the experiment. The effect of drought stre ss to plants on aphid performance was not significantly different betw een the clones tested. Drought stress had no effect on aphid developme nt time, nymphal mortality, the weight of teneral adults and the numbe r of embryos in teneral adults up to the onset of reproduction in the first F-1 generation. The subsequent reproductive capacity, as measure d by the effective and potential fecundity, and the reproductive rate, were much reduced on drought-stressed plants. However, there was only a small decrease in the intrinsic rate of increase (r(m)). Overall th e clone of R. padi from Spain performed better than that from England, the development and prereproductive times being shorter and the fecun dity higher in the Spanish clone, giving a higher r(m). There were no differences in the fecundity and the r(m) between the Spanish and the English clones of S. avenae. The proportion of the F-2 generation that was alate differed greatly between clones, and only the English S. av enae produced significantly more alatae on drought-stressed than on un stressed plants.