Managing barley yellow dwarf virus in cereals

A yield-robbing disease of cereals including wheat, barley, oats, rye and triticale is barley yellow dwarf virus (BYDV). The amount of yield lost depends on the aphid activity, virus presence and strain, cereal growth stage at infection and climatic conditions.

The main vectors for transmitting BYDV are bird cherry aphid (Rhopalosphum padi) and rose grain aphid (Metopilophium dirhodum). They do not pass the virus onto their offspring, rather they acquire it through feeding on infected host plants like volunteer cereals or grass weeds. Once the aphid is carrying the disease it takes 12 to 48 hours before it can be transmitted to emerging cereals.

Seed treatments provide up to 10 weeks of protection from BYDV including while the seed is underground. Aphids can also feed on crop roots, potentially transmitting the virus before the cereal has emerged.

To manage this disease, focus on both cultural and chemical controls. Insecticide applications should be considered as the last line of defence and used in conjunction with seed treatments.

By alternating the insecticide mode of action, using the correct label rate and utilising products that are less harmful to beneficial insects, the risk of insecticide resistance is reduced.

Early-sown autumn crops are most at risk of BYDV when weather conditions are favourable for aphid flights. For the same reason, spring-sown crops can also be at risk as the weather warms and aphid flights commence after winter.

The earliest symptoms of BYDV are discolouration of younger leaves, with barley and wheat turning yellow. Purpling of upper leaf tips can occur too. Oats generally turn purple. As the season progresses the plants will be stunted, show extensive tillering, delayed ear emergence and ripening. The grain will be of poor quality, and as with most pest damage, present in patches across the paddock. Unfortunately, once the patches appear, the damage cannot be rectified.

BYDV management techniques

• Only sow insecticide-treated seed whilst they are still available.
• Destroy all green bridges four to five weeks before cultivating and sowing cereals.
• Delay drilling potential high-risk paddocks too early in the autumn such as second wheats.
• Select BYDV tolerant varieties.
• Manage aphid numbers and spread before GS32 as the crop is much less likely to be infected after this stage.
• Use an insecticide that will not harm beneficial insects. Remember the best way to control an insect is with another insect. Rotating your insecticide mode of actions helps prevent resistance.
• Minimise general stress to plants with the appropriate use of trace elements. Plant health is vital in the fight against diseases.
• Strip tillage and minimal tillage can benefit natural enemies with the retained straw.
• Use Insecticides at full rates to give greatest knockdown and leeway persistence. It is also advised to use an appropriate adjuvant with insecticides to increase efficacy.

For assistance developing a management plan for barley yellow dwarf virus in your cereal crops, contact your local PGG Wrightson Technical Field Representative.