Crop virus revelation

Growers across Australia are well aware of the potential destructive nature viruses can have on their crops.

Viruses often cause reduction of yield and quality, or even complete crop failure.

In a study published in the scientific journal Plant Disease, scientists from Agriculture Victoria in Horsham showed a higher incidence of yellow dwarf viruses in wheat and barley crops in Victoria than had previously been reported in the 1980s.

The findings suggest yield losses due to yellow dwarf infection might also have been higher than estimated.

Dr Piotr Trebicki, who co-authored the study, said the findings were the result of four years of Agriculture Victoria research, co-invested by Grains Research and Development Corporation.

“Over the past four years, we surveyed randomly selected cereal fields across Victoria to understand virus infection levels, incidence and distribution,” he said.

“All collected plant samples were tested in the lab for a range of viruses, which gave us a great insight into the current disease levels and also allowed us to compare our results to studies conducted more than 30 years ago.”

Overall, the Wimmera and south-west of Victoria were found to be the hot spots for cereal viruses, with a 17-fold increase in virus incidence over the Mallee, which is typically hotter and drier.

“In each year of the study, less virus was found in the Mallee than the Wimmera and southwest,” Dr Trebicki said.

“Weather conditions, including rain and temperature during and before the growing season, largely influence virus and aphid levels, which influences the number and severity of infected cereal crops.”

The incidence of yellow dwarf viruses varied considerably between years.

Dr Trebicki said this highlighted the importance of regularly monitoring not only for viruses but the aphids that transmitted them, and ideally for multiple years.

“Plant viruses are difficult to control, because there is no treatment to cure the plant when it is already infected, therefore prevention and minimising its spread is key,” he said.

“As viruses rely on vectors to spread them across the crops, aphids, which are small sap-sucking insects, are mostly responsible.”

Although Agriculture Victoria researchers have a few theories, Dr Trebicki said this worrying trend of increasing virus incidence was not well understood.

“We need to revisit how we evaluate the yield losses because they might currently be underestimated,” he said.

“Growers have quite a few options up their sleeves to protect crops from virus and aphid infestation, but their effectiveness can vary under different growing conditions and therefore needs to be better understood.”

“Plant viruses are difficult to control, because there is no treatment to cure the plant when it is already infected, therefore prevention and minimising its spread is key” – Dr Piotr Trebicki