The yellow dwarf cereal diseases are classified as Barley Yellow Dwarf Virus (BYDV) or Cereal Yellow Dwarf Virus (CYDV). They are cereal viruses that mainly affect Barley, Wheat & Oats. Neither of the viruses are air, seed or soil-borne, however BYDV is more common than CYDV. Both viruses are members of the Luteoviruses, a group of five closely related virus strains. These viruses vary in severity, are spread by different species of aphids, and affect different crops.
BYDV is transmitted by over 20 different aphid species, including the bird-cherry oat aphid, the rose-grain aphid, the corn leaf aphid, the English grain aphid and the green bug. Interestingly, the Russian wheat aphid is not a carrier of BYDV. The virus is picked up by aphids within 15 minutes of feeding on a previously infected plant, and it takes about 12-48 hours before the aphid is able to transmit the infection to other plants.
BYDV is most damaging in higher rainfall areas, where the virus is maintained in permanent grasses and pastures over summer. It is also more prevalent following a wet summer and autumn, which generally promotes a build-up of aphids. Again, in areas with more than 500mm of rain, infection rates are more severe, resulting in early crop infection, harsh symptoms and high yield losses. Though BYDV is more serious in higher rainfall areas, it can occur in all cropping regions, and it affects cereal crops worldwide.
Symptoms of BYDV can take over 3 weeks to appear after infection. The virus usually occurs on single plants or in patches throughout the crop, depending on where the aphids have landed. If the aphids are crawling from an adjoining paddock, symptoms will be visible along the fence line first.
BYDV symptoms vary depending on the crop. They can be confused with symptoms of wheat streak mosaic, nutrient deficiency, waterlogging, root and crown diseases and environmental stress. BYDV can be diagnosed by the presence of aphids and the occurrence of symptoms in patches.
|Bright yellow discoloration of the leaves, starting at the tip and moving towards the base
|Pale yellow stripes between the leaf veins
|Abortion of florets
|Chlorotic (pale or yellow/white) blotching of younger leaves
|Red discoloration of leaf tips (Only in some varieties)
|Poorly developed tillers & sterile heads
|Orange/Brown blotches on the leaves
|Complete bright red discoloration of the leaves, especially on older leaves
|Weak tillers & Abortion of florets
|Yellow stripes or orange coloration on younger leaves
|Yellow leaf discoloration. Can be either a slight mottling, or a bright yellow colour
|Poorly developed tillers
|Pale striping between the veins in young leaves
|Dead leaf tips
|Red discoloration of flag leaves, and streaks at leaf tips
Yield Losses from Barley Yellow Dwarf Virus
Trial data from the Victorian Department of Primary Industries Field Crops Pathology Group (Horsham, 1984) has shown that yield losses of up to 79% can occur when plants are infected before tillering. Later infections can also cause a high yield loss of 6-9%. In South Australia, a trial conducted by Trent Potter showed yield losses in wheat of up to 40% in 2008. In other years, losses varied between 10 and 20%.
Depending on the crop variety and its tolerance or susceptibility to BYDV, early infection can cause low yields, increase screenings and reduce market options.
Spread of BYDV
Yellow dwarf viruses are maintained throughout the summer months in permanent grasses and pastures. The main BYDV hosts during the summer are perennial ryegrass, kikuyu, paspalum, couch and African love grass.
During autumn, aphids will migrate from these infected grasses to cereal crops. The most severe infections are caused throughout the early growing season, when crops are most susceptible to damage.
Widespread epidemics and infections of entire crops are most likely to occur after a wet summer followed by a mild autumn and winter. Peak infection times will be when crops have emerged and the weather is not severe enough to stop aphid movement.
However, though wet conditions are ideal for the spread of BYDV, farmers should not be complacent as the aphids are able to survive in hot and dry conditions, and infections can be spread quickly by relatively few aphids.
Management & control
The best management strategy for BYDV is prevention. Crops should be monitored for symptoms throughout the growing season, but it is critical to have control methods in place before sowing. The most common methods are:
- Using resistant seed varieties
- Delayed sowing
- Chemical treatments
Once symptoms appear, it is too late for control measures – infection and damage have already occurred.
Prevention of any infection is always the best method, and that continues to be true for BYDV. A few simple strategies to prevent the spread of the virus are:
- Controlling grassy weeds. This will minimise the virus and aphid populations in surrounding areas, effectively limiting the chances of infection to your crop
- Utilising insecticides. While this may not prevent initial infections, it can limit the spread of the virus through your crop
Delayed sowing allows growers to avoid the main aphid flights and migrations during autumn, which reduces the likelihood of BYDV infection. However, the benefits of delayed sowing need to be compared to the potential yield loss resulting from late sowing.
When available, resistant varieties of seed are the preferred management option for BYDV. They are the most effective control to prevent infection, rather than cure plants that are already infected. Refer to your agronimist to determine whether resistant and tolerant seed varieties would be appropriate for your cropping program.
Sowing these tolerant varieties is the most effective way to reduce yield losses from the BYDV. High levels of resistance and tolerance may not be available, however a lower susceptibility to the disease minimises the potential for severe infection and yield losses.
The most effective way to prevent, control and manage BYDV is to treat your seeds prior to sowing. In situations where aphids are likely to be prevalent, insecticides can be used for protection throughout the germination and establishment phase.
Seed treatments are known to reduce aphids in cereal crops at the early stage of growth when cereals are most susceptible to BYDV. If aphids are found during plant establishment, chemical sprays can also be used to control the feeding damage of aphids and reduce the spread of BYDV infection.
Combatting BYDV at csg
Here at csg, we offer seed services including cleaning, grading and treating. These processes improve yield and protect seedlings from insect damage and diseases, including BYDV. We recommend using seed treatments as the most effective way to prevent or minimize the negative affects of BYDV, while supporting the growth of seeds and encouraging healthy crops.
References & Useful Articles
- Barley Yellow Dwarf Virus Fact Sheet | GRDC
- Managing barley yellow dwarf virus and cereal yellow dwarf virus in cereals | Dept. of Primary Industries WA
- Barley yellow dwarf virus | Agriculture Victoria
- Barley Yellow Dwarf Virus (BYDV) | Crop Science // UK
- Management suggestions for barley yellow dwarf virus control | Michigan State University