Yellow dwarf virus hits

Yellow dwarf virus hits

Grains
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Farmers are contending with a high load of yellow dwarf virus this year following ideal conditions for the disease's build up over autumn.

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Yellow dwarf virus can hit barley especially hard.

Yellow dwarf virus can hit barley especially hard.

MOST grain growers were thrilled with the good autumn rain, but there has been a downside - an increase in yellow dwarf virus (YDV) in cereal crops.

Agriculture Victoria announced there had been a spike in YDV this year, particularly in the Wimmera and southern Mallee, while officials in other states are also closely monitoring the situation.

YDVs are a group of closely related virus species that infect cereals such as wheat, barley, oats, triticale and grasses, with barley YDV the best known to farmers.

These widespread viruses can cause yield losses of up to 80 per cent when plants are infected early in the growing season.

Ag Vic molecular epidemiologist Narelle Nancarrow said the virus presented in distinctive ways.

"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," Ms Nancarrow said.

"Leaf discoloration is typically bright yellow in barley, yellow and/or reddish in wheat and red in oats," she said.

Symptoms can take around three weeks to appear after infection, however many infected grasses are symptomless, meaning the disease can be wider spread than farmers realise.

Another difficulty in identifying the disease is the fact the damage can present very similarly to nutrient deficiency.

Ms Nancarrow said a distinguishing feature was that 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.

Like many plant viruses, YDV is spread by aphids, usually the oat and corn aphid species.

The viruses and aphids survive between seasons in volunteer cereals or pasture grasses.

Last summer and autumn, with good rain allowing a green bridge, was a perfect scenario for YDV carryover.

Ms Nancarrow said controlling the green bridge was one of the best ways of lowering the YDV risk.

"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.

Further on into the season she said farmers could consider an insecticide if aphid loads were particularly high, but she said that had to be weighed up against potential insecticide resistance and the effects on beneficial insects.

The story Yellow dwarf virus hits first appeared on Farm Online.

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