Early control helps beat blight

EARLY POTATO blight control can help protect crops throughout the season, according to Scottish Agricultural College research.

Applying the first blight spray between 70% emergence and soon after crops have met along the rows can protect against zoospores washed through the soil later in the season, said the SAC‘s Ruairidh Bain.

“There appears to be a long term benefit in starting the programme with a blight fungicide that has powerful zoospore activity and will remain active in the soil even at low concentrations,” he said.

Treating crops at an early stage enables sufficient spray to reach the soil surface, compared to later in the season when more is intercepted by the crop canopy, he explained.

Early protection may also be particularly valuable where infected tubers have been planted, added Syngenta potato manager, Garth Bretherton.

“The effects are most pronounced in wet soils, where blight zoospores can move freely in the soil moisture.”

But Dr Bain warned that in particularly wet years, prolonged exposure to infection and the sheer number of zoospores could overwhelm the protective activity from early applications.

Mr Bretherton recommended growers use Shirlan (fluazinam) during early crop emergence to stop zoospore movement and prevent spore germination.