Early T0 key to rhyncho fight

Applying an early T0 fungicide could pay dividends for winter barley growers in high rhynchosporium-pressure areas, according to the Scottish Agricultural College’s Simon Oxley.

Four years of SAC trials over a range of disease pressure sites found an average 0.3t/ha benefit from an early T0 spray applied at growth stage 25.

“This March treatment also kept disease levels lower over the subsequent months and could provide the grower with more flexibility in reducing fungicide dose in follow-up treatments.”

Fungicide cost

What’s more, with higher grain prices, the value of this extra yield more than covered the fungicide cost, he said.

“With barley at £175/t, the March fungicide in high disease pressure situations will achieve an additional £51/ha from a fungicide spend of £19/ha.”

GS49 spray

About 20% of the overall fungicide response came from the early treatment in winter barley, with the key GS 31-32 treatment accounting for around 40% and the remainder being made up by the final GS49 spray, he added.

“In spring barley, it’s the other way around the best response comes from the later GS49 timing.”

When calculating disease risk, growers, particularly those in higher-risk areas of northern Britain, should be cautious about placing too much faith in variety resistance ratings, Mr Oxley continued.

“Current HGCA winter barley ratings are a poor predictor of rhynchosporium risk. A lot appear quite resistant with ratings of eight or nine, but the official [Recommended Lists] disease assessments take place later in the season, when a lot of disease has passed.”

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