Comparative biology of three cereal aphids on TAM 107 wheat

Greenbug, Schizaphis graminum (Rodani); bird cherry-oat aphid, Rhopalosiphum padi L.; and Russian wheat aphid, Diuraphis noxia (Mordvilko), developed and reproduced successfully on TAM 107 wheat (Triticum aestivum L.) from 21.0 to 22.6degreesC when transferred to individual plants as single first instars. Both D. noxia "foundresses" and second-generation nymphs developed slower than those of S. graminum and R. padi. In all three species, nymphs developed faster in small colonies of siblings than did their foundress mother developing in solitude. However, when nymphs developed in solitude, only those of S. graminum developed faster than their mothers on the same plants, suggesting maternal induction of plant suitability. Isolated nymphs of D. noxia did not differ in developmental rate from their mothers on maternal plants,and those of R. padi developed more slowly, suggesting that effects of group feeding were responsible for the faster development of second-generation nymphs observed within growing colonies of these species. D. noxia cumulative foundress fecundity and daily reproductive rate were lower than those of S. graminum and R. padi. The estimated intrinsic rates of increase were S. graminum > R. padi > D. noxia. The preferred feeding location of S. graminum foundresses was the primary leaf, whereas for R. padi, it was the stem, and for D. noxia, it was the upper leaves, primarily the terminal leaf. Foundresses of R. padi were observed to change position on the plant from day to day more often than did those of S. graminum or D. noxia. R. padi colonies initiated from 10 first instars accumulated more biomass over a 10-d period than did those of S. graminum or D. noxia.