Feeding and multiplication of three cereal aphid species and their effect on yield of winter wheat

Sitobion avenae F. multiplies at a higher rate on winter wheat than Rhopalosiphum padi L. and Metopolophium dirhodum Wlk. Unlike the other two species S. avenae prefers the ear, where it multiplies twice as quickly as on the flag leaf. Infestation of the ear rather than of the leaves leads to reduction of the average grain weight. These results suggest that S. avenae is the most injurious. In 3 field trials with this aphid fungal growth on honeydew caused about half of the damage. After correction for the fungus effect, the loss in yield caused by S. avenae feeding on the ear did not differ much from that calculated from its energy budget. Therefore, it is concluded that stylet insertion and saliva injection have no important influence on the growth of grains. From results with long living and highly productive crops it seems that honeydew can cause a more serious loss in yield if the crop does not prematurely ripen under the influence of various other yield-reducing factors.