Ear structure and the resistance of cereals to aphids

In 1977 and 1978 in the field the cereal aphid Sitobion avenae F. (Hemiptera:Aphididae) was a pest on winter wheat (cv. Maris Huntsman), but was rare on winter barley (cv. Maris Otter). The results of laboratory experiments can only partly account for this observation. Alates showed no preference between leaves of wheat and barley, flag leaves of wheat and ears of barley, or ears of wheat and barley, the developmental stages available for colonization in the field. Developmental time, teneral weight, reproductive rate and offspring size of apterae were similar when reared on ears of wheat and barley. However, the proportion that developed into alatae and adult mortality were significantly higher on barley. That aphids fed on the rachis of wheat and the glumes of barley was attributed to differences in the ear structure of the two cereals. The possible role of plant structure in determining the resistance of cereals to aphids in the field is discussed.