Observations on the morphs of Macrosiphum avenae and Metopolophium dirhodum on cereals during the summer and autumn

SUMMARY From June to early August 1970, populations of Macrosiphum avenae and Metopolophium dirhodum on marked tillers of field barley were compared with the numbers of alatae trapped at crop height and at 12.2 m. There were always more M. dirhodum than M. avenae on the tillers. Only apterae were produced until mid‐June when both alatae and apterae occurred; after mid‐July only alate M. avenae were found. Until mid‐June most of the flying alatae were caught at 12.2 m as they migrated from spring hosts to cereals. Thereafter, more alate M. avenae were trapped at 12.2 m than at crop level, whereas numbers of alate M. dirhodum were usually comparable at both heights. Although crop and flying populations occasionally showed temporal similarities, insufficient is known about their field distribution and the factors affecting their alate production and flight activity to interpret this relationship. In the autumn, two consecutive reproductive phases of M. dirhodum occurred on winter wheat grown in pots outdoors. Initially, apterous virginoparae and alatae, probably sexuparae, were produced, whereas only alate males appeared during the second phase. In contrast, M. avenae deposited mainly apterous virginoparae although some oviparae developed in October to lay scattered, probably infertile eggs on the tillers.