TRANSMISSION OF BEAN COMMON MOSAIC-VIRUS BY CEREAL APHIDS (HOMOPTERA,APHIDIDAE)

Bean common mosaic potyvirus (BCMV) is aphid-transmitted in a nonpersi stent manner. BCMV can be subdivided into two serotypes, A and B. BCMV serotype A has been identified in Idaho as the cause of seed lot reje ctions and occasional crop failures in recent years. We suspected that cereal aphids could be important vectors of BCMV because they compris e a large proportion of airborne alate aphids in Idaho as measured by the Idaho suction trap survey system. Five species of cereal aphids-Di uraphis noxia, Metopolophium dirhodum, Rhopalosiphum padi, Schizaphis graminum, and Sitobion avenae-were tested along with Myzus persicae fo r efficiency of transmission of BCMV using timed acquisition probes: D . noxia, Metopolophium dirhodum, and M. persicae were tested in mass i noculation experiments, and winged D. noxia and M. persicae were teste d further in an arena setting. All aphid species tested transmitted th e virus in all three experiments except D. noxia, which appears to be a nonvector. Transmission efficiencies and average suction trap collec tions in bean production areas were combined to produce a potential ve ctor index (PVI). Trap collection data for 1989-1992 showed a high cor relation between the PVI and the number of hectares of seed beans reje cted because of virus infection (r2 = 0.96, P = 0.018). Prior to that (1985-1988), the correlation was poor in that far fewer hectares were rejected than predicted by the PVI.