Winter barley still an option in NI, but BYDV risk rises

Winter barley planting remains a live option in Northern Ireland, with Co. Down singled out as the area where growers can still achieve high establishment rates, according to CAFRE crops specialist Leigh McClean.

Her verdict comes with a catch. The same warm, settled conditions that make late drilling attractive also raise the risk of Barley Yellow Dwarf Virus (BYDV), a disease she described as a significant yield robber spread by migrating, infected aphids feeding on newly emerged seedlings.

"Soil conditions have remained excellent over recent weeks, which has allowed growers to get on with the planting of winter cereals in a very effective manner," McClean said.

Why the weather cuts both ways

Until recent days brought a sharp cooldown, average daily temperatures had run well above the norm for the late September and early October period. Early sowing plus settled weather improves the odds of successful establishment. It also extends the window in which aphids can find and infect young seedlings.

The threat arrives on two routes. Non-winged aphids move in from old crop residues and field margins. Winged aphids travel from much greater distances. Either way, the result for an unprotected crop is the same.

How growers can track the threat

The Agri-Food and Biosciences Institute (AFBI) runs weekly aphid monitoring using a suction trap at Crossnacreevy and publishes the results online. AFBI principal scientific officer Daniel Leybourne said the data gives growers a benchmark.

"Aphid monitoring gives growers an indication of aphid numbers comparable to previous weeks and how the current season compares to the previous year and long-term average," he said.

"Growers can use this information along with their farm situation to assess the risk to their own crops."

Risk is not evenly spread. Fields in milder locations, sheltered sites at lower altitudes, ground near the coast, and anything drilled early all carry a higher chance of BYDV infection.

Growers also have a new planning aid. The AHDB has launched a BYDV risk tool that takes a field location and a planned sowing date and estimates disease risk. Used after drilling, it accepts the crop emergence date instead, then summarises the risk and indicates when to act.

What does this change for spray decisions?

Plenty, as it happens. The advice from both bodies is to piece together the trap data, the AHDB tool output and your own field walking before reaching for the sprayer.

Where aphids are present and BYDV risk is high, a single pyrethroid application at the 2-3 leaf stage is effective in controlling aphids and reducing infection levels in October-sown cereals. Higher-risk September-sown cereals may justify a second spray to protect yield if mild, settled conditions persist late into the autumn.

There is a hard limit, though. CAFRE and AFBI both warn that multiple pyrethroid applications should be avoided, because they accelerate pyrethroid resistance in the aphid population and make BYDV control harder in future seasons. Spend the chemistry carefully now, or pay more later.

For growers still weighing the drill, the message is straightforward: the door is open, particularly in Co. Down, but the AHDB tool and the weekly AFBI suction trap results deserve a look before the next pass across the field.