Control of subterranean clover red leaf virus in broad bean crops with aphicides

SUMMARY Trials at three sites in north‐western Tasmania monitored the spread of subterranean clover red leaf virus into and within broad bean crops with movement of its vector, Aulacorthum solani. Records indicated that almost all infections within the crops resulted from secondary spread by apterae following the establishment by migrant alatae of a very few foci of infestation and infection soon after crop emergence. Spread of the virus within the crops was reduced by sprays of demeton‐S‐methyl. Incidence of infection in sprayed plots at harvest was 23%, 13% and 23% at the three sites compared with 80%, 31% and 84% respectively, in unsprayed plots. Yield increases as a result of spraying were 980, 420 and 540 kg/ha.