Assessment of methods for testing varietal resistance to aphid s in cereals

The adult weight of three species of cereal aphids on barley was correlated with the number of large embryos and the total number of embryos within newly moulted adults. The relationships between embryo number and weight were constant for each species of aphid on all seven varieties of barley under identical conditions. The weights of aphids of each species on seven varieties of barley were significantly different from each other in each experiment. Pot size and plant age had a significant effect on the weights of Rhopalosiphum padi. The validity of these tests compared with previous methods is discussed.