Using electrical penetration graphs to monitor aphid feeding, it was shown that volatiles of a non-host plant (alfalfa, Medicago sativa L.) did not disrupt the process of host acceptance by alate virginoparae of the birdcherry-oat aphid, Rhopalosiphum padi L., once it was settled on a host plant (wheat, Triticum aestivum L.).
The pattern of cell punctures in the electrical penetration graph was studied from the start of a probe leading to the first phloem phase by the aphid Sitobion fragarine (Walker) (Sternorrhyncha: Aphididae) on two cultivars of the wheat, Triticum aestivum L., differing in hydroxamic acid concentration. In addition, the spatial arrangement of cells in the leaf of the host plant was histologically observed and the number of cells between the epidermis and phloem counted. The results suggest a feeding deterrent effect of hydroxamic acids and a constant styler puncturing activity into plant cells.