Honeydew production and sap ingestion by the cereal aphids Rhopalosiphum padi and Metopolophium dirhodum on seedlings of resistant and susceptible wheat species

Measurements of the frequency and rate of honeydew excretion by Rhopalosiphum padi and Metopolophium dirhodum, feeding on seedlings of resistant and susceptible wheat (Triticum monococcum and T. aestivum) were used to estimate the quantity of sap ingested over 24 h. Ingestion was significantly reduced on the more resistant T. monococcum and for M. dirhodum this may be due in part to a reduction in the success of phloem location.