Plant viruses are economically important pathogens, reducing yield and quality of many agricultural crops. There are over 700 known plant viruses that can cause serious damage to the plants they infect. Globally, plant viruses can cause a complete crop failure even with updated pest and disease management measures. In this chapter the main virus diseases of pulses, canola and cereals, their symptoms, virus cycle and management are discussed.

Viruses cause a variety of symptoms in plants they infect and can be present in plants without showing any symptoms. The common virus symptoms are local lesions, mosaic patterns, yellowing, leaf rolling or curling, ringspots, necrosis and total death of plant.

Some viruses are seed-borne, others are mechanically transmitted however, most viruses are transmitted by insect vectors.

The main non-persistant viruses in pulses are: Alfalfa mosaic virus (AMV), Bean yellow mosaic virus (BYMV), Cucumber mosaic virus (CMV) and Pea seed- borne mosaic virus (PSbMV), in cereals: Wheat streak mosaic virus (WSMV) and in canola: Turnip mosaic virus (TuMV).

The main persistent (phloem limited) viruses infecting pulses are: Beet western yellows virus (BWYV), Bean leafroll virus and Subterranean clover stunt virus (SCSV), in cereals: Barley yellow dwarf virus (BYDV) and in canola: T urnip yellows virus (synonym-BWYV).

The main virus vector aphid species in our region are green peach aphid ( Myzus persicae ) and bird cherry- oat aphid ( Rhopalosiphum padi ), (Figures 10.1 and 10.2).

Figure 10.1 Green peach aphid ( Myzus persicae ); a common vector of pulse and canola viruses

Figure 10.2 Bird cherry-oat aphid ( Rhopalosiphum padi ); a common vector of cereal viruses