Aphididae) on Fungal Endophyte-Infected and Uninfected Perennial Ryegrass

The behavior and performance of the Russian wheat aphid, Diuraphis no&r (Mordvilko), on fungal endophyte-infected and endophyte-free perennial ryegrass, Lolium perenne L., was investigated in the laboratory and field. Aphids did not select endophytefree over endophyte-infected leaf sheaths and stem segments in petri dish preference tests. Similarly, the probing behavior of D. noxia on endophyte-free and infected L. perenne did not vary in laboratory tests. However, compared with aphid counts on endophyte-free plants, counts on infected plants were significantly lower on the first day and thereafter in laboratory population growth tests. Numbers of D. noxia were higher on endophyte-free plants than on infected plants of L. perenne in replicated field plots. The results are discussed in relation to the possible mechanisms of resistance involved, our knowledge of the performance of other cereal aphids on endophyte-infected grasses, and the use of endophytic fungi as aphid biocontrol agents.