Physiological modification of the host feeding site by cereal aphids (Homoptera:Aphididae)

Indole-3-acetic acid-1(14)C C and C-14-sucrose labels were used to study the effects of greenbugs, Schizaphis graminum (Rondani), and Russian wheat aphids, Diuraphis noxia (Mordvilko), on phloem function of wheat (Triticum aestivum L.). Greenbug feeding significantly reduced translocation from the immediate feeding site; however, phloem integrity was not impeded. In contrast, Russian wheat aphids had little effect on vein loading or phloem translocation at the feeding site. Similar results were obtained when resistant and susceptible wheats were infested with three different greenbug biotypes. Greenbugs fed artificial diets containing C-14-sucrose injected salivary material that was trauslocated to both root and shoot systems. The accumulation of salivary constituents in the roots of wheat seedlings fed upon by greenbugs may account for the significant reductions in root biomass that have previously been reported.