Potato growers could face a repeat of last August’s high blight pressure, so tuber protection should be the focus of programmes from here on, according to Bayer CropScience.

After a welcome slow start, the number of blight incidents confirmed during July has been building week on week and all potato-growing areas are now affected. In the week ending July 18, the Potato Council recorded a dozen incidents and since then wet, blight favourable conditions have persisted.

Neil Thompson, Bayer’s product manager for blight fungicides, has suggested the current situation indicates that disease development is likely to follow a similar pattern to last season. He said: “If blight favourable conditions continue, this year’s slow start could well be followed by a similar late epidemic taking off in August.

“Main crops are now well past canopy complete and with tubers developing fast, the focus of programmes should switch from foliar to tuber blight protection,” he advised. “The latest Euroblight table, updated in December 2008, provides the definitive fungicide ratings to inform selection for tuber protection.”

On the Euroblight scale of one to three both products - Infinito and Ranman - hold the maximum three rating for ‘very good effect’ in fighting tuber blight with fluazinam wand Revus behind them.

Thompson said: “The ratings speak for themselves. Under high blight pressure, continuing with weaker tuber protection products is risky. With Infinito, growers don’t have to compromise on any aspect of control as it gained the highest overall rating of all fungicides assessed, including a first equal rating for foliar blight effectiveness.

“Trials comparing the kick-back performance of Infinito, Ranman and Revus, used alone and with cymoxanil added in, have confirmed that this is not necessary, providing it is used as recommended. Last August, in a curative activity trial, Infinito alone proved highly effective, and it was only with the addition of cymoxanil that the efficacy of Ranman and Revus came close to it.”

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