BEHAVIOR AND PERFORMANCE OF DIURAPHIS-NOXIA (HOMOPTERA, APHIDIDAE) ONFUNGAL ENDOPHYTE-INFECTED AND UNINFECTED PERENNIAL RYEGRASS

The behavior and performance of the Russian wheat aphid, Diuraphis nox ia (Mordvilko), on fungal endophyte-infected and endophyte-free perenn ial ryegrass, Lolium perenne L., was investigated in the laboratory an d field. Aphids did not select endophyte-free over endophyte-infected leaf sheaths and stem segments in petri dish preference tests. Similar ly, the probing behavior of D. noxia on endophyte-free and infected L. perenne did not vary in laboratory tests. However, compared with aphi d counts on endophyte-free plants, counts on infected plants were sign ificantly lower on the first day and thereafter in laboratory populati on growth tests. Numbers of D. noxia were higher on endophyte-free pla nts than on infected plants of L. perenne in replicated field plots. T he results are discussed in relation to the possible mechanisms of res istance involved, our knowledge of the performance of other cereal aph ids on endophyte-infected grasses, and the use of endophytic fungi as aphid biocontrol agents.