There has been an increase in identified symptoms of Yellow Dwarf Virus (YDV) infection in cereal crops in the Wimmera and southern Mallee regions.
YDVs are a group of closely related virus species that infect cereals such as wheat, barley, oats, triticale and grasses. These widespread viruses can cause yield losses of up to 80 per cent when plants are infected early in the growing season.
Agriculture Victoria Molecular Epidemiologist Narelle Nancarrow said there is little that can be done once a plant is infected with the virus, therefore prevention and management are vital.
“Typical symptoms of YDV infection include stunted growth and yellow or red leaf discoloration that starts at the tip of the leaf and spreads towards the base.”
“Leaf discoloration is typically bright yellow in barley, yellow and/or reddish in wheat and red in oats,” Ms Nancarrow said.
Symptoms can take around three weeks to appear after infection, while many infected grasses are symptomless.
Ms Nancarrow said although it can be difficult to distinguish symptoms of YDV infection from those caused by nutrient deficiencies or other plant stresses, plants infected with YDV are usually stunted with bright yellow or red leaf tips, are often most noticeable on the edge of the crop or as random plants scattered throughout the crop, and are frequently surrounded by healthy green plants.
“Patches of yellow or red stunted plants can be also attributed to virus infection as a result of secondary infection,” Ms Nancarrow said.
YDV are transmitted from infected to healthy plants by aphids, most commonly the oat and corn aphid. The viruses and aphids survive between seasons in volunteer cereals or pasture grasses.
Ms Nancarrow said conditions have been favorable for YDV in the Wimmera and southern Mallee regions with the emergence of grasses and volunteer cereals following rains in late summer and early autumn, as well as aphids being active since early in the season with populations likely to increase as summer approaches.
“It’s important to control the grasses and volunteer cereals around the crop that could potentially be reservoirs for viruses and aphids, and to monitor crops regularly for the presence of aphids, virus symptoms and beneficial insects,” Ms Nancarrow said.
Management options include use of an appropriate insecticide if aphid numbers are high, particularly at sowing or early in the growing season, taking into consideration insecticide resistance and the effects on beneficial insects.
More information about Yellow Dwarf Virus can be found on the Agriculture Victoria website: https://agriculture.vic.gov.au/biosecurity/plant-diseases/grain-pulses-and-cereal-diseases/barley-yellow-dwarf-virus.
Source: Agriculture Victoria