Light leaf spot has been widely recognised as a Scottish problem, though it has more recently been viewed as an issue across the UK, with increasing problems arising for other brassica crop growers in the winter months.

Now, Syngenta’s ‘Brassica Alert’ disease warning system is spore trapping for the pathogen to provide valuable notification of risks and better manage spray timings. This will allow brassica growers to maintain the same yields and crop quality using two or three fewer fungicide sprays over the season, it has been claimed.

Managed by the Allium and Brassica Centre, these alerts will highlight pathogen risks through a combination of weather data and active spore trapping for ringspot, white blister and now light leaf spot.

By registering for Brassica Alert, growers and agronomists can incorporate the information to devise appropriate fungicide strategies and timings, advised by Syngenta field technical manager, Simon Jackson.

“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 a mild autumn. However, light leaf spot remains active at far lower temperatures, down to 4°C, so continues to cause outbreaks right through the winter,” he warned.

“It’s of particular concern to Brussels sprout growers, with the pathogen continuing to spread further south and across Lincolnshire in recent seasons.”

Wet weather can be a precursor to spore release, making this season a greater concern for brassica crop growers, especially in areas where OSR stubble trash has been left on the surface with direct drilling of subsequent cereal crops.

Mr Jackson’s experience of light leaf spot spore monitoring in Scotland has shown spore release and aerial movement right through the winter. “Once infection is in the crop, uncontrolled, it will continue to develop and spread by rain splash in wet conditions. Knowing the risk and timing of spore infection can significantly help with preventative fungicide timing and keeping the crop clean through the winter,” he advised.

Carl Sharp, an agronomist at the Allium and Brassica Centre, believed that ‘Brassica Alert’ will give 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.

“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 reported.

He also highlighted that the symptoms of light leaf spot have typically been seen from mid-October onwards, but its appearance is extremely weather dependent, which will make the forecasting most valuable.