Yield losses
BYDV and CYDV infection is most serious in cereal crops when plants become infected before tillering. In susceptible cereal varieties, where the entire crop is infected soon after sowing, yields of wheat, barley and oats can fall by up to 80%. Moreover, the amount of shrivelled grain increases, and this can affect marketable yield. If the crop is infected late, yield may be reduced by only 10-20%. Trials with wheat in WA have shown that yield losses caused by BYDV infection vary greatly between varieties depending on their tolerance or susceptibility to the virus. Yields of sensitive varieties were reduced by up to 67%. Similar losses develop in barley and oats.
Control
The best way to control BYDV and CYDV is to use appropriate management strategies.
Sowing of resistant varieties
Sowing resistant varieties is the most effective method of reducing losses. See crop variety guides for susceptibility ratings.
Insecticides
Strategic applications of insecticides can be used against the aphids that carry BYDV or CYDV to reduce its spread. It is important to protect the crop during the first 10 weeks after emergence. First pyrethroid spray: three weeks after emergence (or 2-leaf stage if aphids easily found). Second pyrethroid spray: seven weeks after emergence. In risk situations, seed dressings containing imidacloprid applied to seed before sowing are recommended for good early season control but requires a follow-up pyrethroid spray.
Delayed sowing
Delayed sowing avoids the autumn peak of cereal aphid activity and reduces the incidence of BYDV. However, delaying sowing generally reduces yields, and this loss must be balanced against the benefit of lower virus incidences.