The mild and wet conditions that have impacted the UK in recent months could provide the perfect conditions for barley yellow dwarf virus (BYDV) in spring barley.
Dr Bill Lankford, herbicide and insecticide technical specialist at ADAMA, explained that an early aphid migration is predicted to coincide with when crops are at their most vulnerable.
“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,” he said.
“However, the mild conditions in January, February and March mean temperatures rarely fell below the minus 5 degrees Celsius needed to reduce aphid populations. And, whilst the majority of spring barley would normally be sown and out of the ground by the end of March, large areas are still to be drilled, leaving significant potential for aphids to find and infect new seedlings as soon as they emerge.”
Modelling work from Rothamsted Research suggests that the first flights of Bird cherry-oat aphid (Rhopalosiphum paid) will take place in the first half of April, while Grain aphid (Sitobion avenae) and Rose-grain aphid (Metopolophium dirhodum) will follow 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,” Dr Lankford said. “As such, 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.”
To protect yields, and any malting premiums in place, growers are being advised to use a suitable aphicide treatment early in their spray programmes.
“In Ireland, where the convergence of aphid activity and crop emergence occurs more frequently, yield losses of 0.5-1.0 tonnes per hectare are commonplace in untreated crops, so it’s worth protecting crops from the outset,” Dr Lankford added.
If the aphid population threshold is exceeded, the best line of defence is to apply an insecticide when the crop is at growth stage 13-14. Dr Lankford recommended products that have a lower impact on beneficials, which will further help to control pests.
“In situations where a pyrethroid pesticide is deemed necessary, MAVRIK® (240 g/litre tau-fluvalinate) not only provides fast-acting contact control of aphids in cereals, but also has a lower residual impact on beneficial insects compared to other pyrethroids,” he said.
“This reduced toxicity enables populations of advantageous insects such as ground and rove beetles, hoverflies, lacewings, ladybirds and parasitic wasps and flies to recover more quickly after crops have been sprayed, therefore ensuring there’s a strong population of predators ready and able to contribute to the control of any subsequent influxes of aphids. MAVRIK also has the added advantage of being very fast-acting which means it halts feeding damage quickly.”
For more information go to www.adama.com