Drought stress and cereal aphid performance

The performance of clones of Rhopalosiphum padi and Sitobion avenae from England and Spain was examined on drought-stressed tillering winter wheat in an environment chamber at 14 ± 1°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 stress to plants on aphid performance was not significantly different between the clones tested. Drought stress had no effect on aphid development time, nymphal mortality, the weight of teneral adults and the number of embryos in teneral adults up to the onset of reproduction in the first F₁ generation. The subsequent reproductive capacity, as measured 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 the clone of R. padi from Spain performed better than that from England, the development and prereproductive times being shorter and the fecundity 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 F₂ generation that was alate differed greatly between clones, and only the English S. avenae produced significantly more alatae on drought-stressed than on unstressed plants.