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Causal organism - Barley yellow dwarf virus
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Direct transfer
Appropriate, timely cultivations - ploughing at least 3 weeks before drilling, burying or destroying trash completely and preparing well consolidated seedbeds will minimise the risk of direct transfer. Applying a desiccant herbicide 7-10 days before cultivation will also give effective control.
Indirect transfer
Late drilled crops are generally less affected than those drilled early and some localities are less BYDV-prone than others. The damage caused by BYDV infection can be minimised by delaying sowing of cereals until the middle of October. In most years such crops escape the aphid colonisation which brings virus so that no preventative spraying need be considered. In some years few crops warrant treatment.
The disease is most effectively controlled in crops at risk by application of aphicides during the autumn or, in very high risk areas, by the use of insecticidal seed treatment (e.g.imidacloprid in Sibutol Secur). The aphid vectors of BYDV can be difficult to find in cereal crops. Inspections are best made on warm, sunny days. At other times the aphids may be hidden within the unopened leaves or on parts of the plant below the soil surface.
If very early drilled crops become infested before mid-October crops should be sprayed immediately with a recommended aphicide. If such crops become reinfested by late October/early November, they will need to be sprayed again. If no aphids are found, but the locality is one in which BYDV has caused significant damage in previous years, a spray is likely to be worthwile in late October/early November. If BYDV has not regularly caused damage in the past, inspect crops again in late October/early November. Spray then if aphids are found.
In later drilled crops (early to mid October) inspections for aphids should be made in late October/early November. If no aphids are found and the weather remains mild, monitoring should continue until late winter. An aphicide should be applied only if aphids are found.
Crops drilled after mid-October are rarely affected by BYDV introduced by winged aphids. However, in very mild Autumns such crops may still be at risk and crops should be inspected in November. If aphids are found, spraying then with a recommended aphicide may be worthwhile. Aphicide use on spring wheat is difficult to justify
