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Syngenta urges growers to be alert for light leaf spot


With light leaf spot causing greater issues for brassica growers over the winter, the Syngenta Brassica Alert disease warning system is now spore trapping for the pathogen. The service, which is managed by the Allium & Brassica Centre, forecasts pathogen risks through a combination of weather data and active spore trapping for ringspot, white blister and now light leaf spot at sites in Lincolnshire.

“Historically growers would maintain fungicide programmes using Amistar Top for ringspot and white blister until temperatures dropped consistently below 10°C – typically around mid-November, but could be extended in mild autumn,” explains Syngenta field technical manager, Simon Jackson. “However, light leaf spot remains active at far lower temperatures, down to 4°C, so continues to cause outbreaks right through the winter. It’s of particular concern to Brussels sprout growers, with the pathogen continuing to spread further south and across Lincolnshire in recent seasons.”

Carl Sharp, agronomist with the Allium & Brassica Centre, believes that Brassica Alert has given growers greater flexibility and confidence in moving from a standard fixed interval fungicide programme, to selected targeted applications using the most suitable products for the timing. “Our independent trials have shown that two targeted applications using Brassica Alert, gave comparative disease control, marketable yield and quality, whilst saving two or three sprays from a standard programme,” he said.

“The combination of climatic data and spore trapping has given consistent results, particularly with Ringspot. We can use a similar model to determine the risk for light leaf spot, to help growers select appropriate controls.”

Picture caption: Simon Jackson

Photo Credit: Syngenta