‘Perfect storm’ warning for BYDV this spring

A mild and wet first three months of the year threaten to result in a perfect storm for barley yellow dwarf virus (BYDV) infections this spring.

Winter temperatures were rarely low enough to reduce populations of virus-carrying aphids – which have started to migrate just as crops are at their most vulnerable, says agronomist Bill Lankford, of Adama.

“In England, the first aphid migration of the year rarely threatens spring barley, as crops are usually far enough ahead that they have advanced beyond their most susceptible 2-5 leaf growth stage,” says Dr Lankford.

Late drilling

“But mild conditions in January, February and March mean temperatures rarely fell below the minus 5°C needed to reduce aphid populations.

While most spring barley would normally be sown and out of the ground by the end of March, large areas were still to be drilled in April – leaving significant potential for emerging aphids to infect new seedlings.

Forecasts from experts at Rothamsted Research suggested the first flights of bird cherry-oat aphid would take place in the first half of April, with grain aphids and rose-grain aphids following soon after.

“That’s two to three weeks earlier than normal, with the number of aphids also predicted to be in the top 25% of historical levels,” said Dr Lankford.

There’s a high risk that barley plants could become infected with the BYDV virus almost as soon as they emerge from the seedbed, with subsequent aphid migrations exacerbating the problem by spreading the virus further into the field.”

Malting premium

To protect yields, and the potential for crops to attain a malting premium, growers have been advised to factor a suitable aphicide treatment into their early season spray programmes.

In Ireland, where the convergence of aphid activity and crop emergence occurs more frequently, yield losses of up to 1t/ha are commonplace in untreated crops, says Dr Lankford.

“It’s worth protecting crops from the outset,” he adds.

If the aphid population threshold is exceeded, it’s best to apply an insecticide when the crop is at growth stage 13-14, says Dr Lankford. A pesticide with a low impact on beneficial insects can further control pest populations, he adds.

Quick recovery

“In situations where a pyrethroid pesticide is deemed necessary, Mavrik provides fast-acting contact control of aphids in cereals with a lower residual impact on beneficial insects compared to other pyrethroids.”

This reduced toxicity encourages the quick recovery of advantageous insects – such as beetles, hoverflies, lacewings, ladybirds and parasitic wasps and flies – after crops have been sprayed.

Advantage

Mavrik has the added advantage of being very fast-acting which means it halts feeding damage quickly. Studies show it also remains stable at higher temperatures compared to alternative insecticides.

“Aphid knockdown and the persistence of Mavrik continued to be robust at 20-25°C –which makes it the more effective option if and when the mercury finally starts to rise,” says Dr Lankford.