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Crop Advice & Expertise

Light leaf spot incidence reaches epidemic levels

Nearly three quarters of samples assessed in January by Bayer’s SpotCheck initiative contained light leaf spot symptoms, 3 days after incubation.

The latest SpotCheck results have followed the trend of increasing light leaf spot levels seen in previous months, suggesting that we are now reaching epidemic levels, says Philip Walker, Arable Plant Pathologist at ADAS. He says that the continued mild and wet weather observed in the previous months has created conditions conducive for the disease to develop.

“This is especially concerning given many farmers have so far been unable to travel, leaving crops without protection over the autumn and winter period,” he says.

“We have seen infection previously, but now both the incidence of light leaf spot infection, and the severity of that infection has rapidly increased. Looking through the results, approximately half of the samples presented infection levels above 25%, and that is normally when we start seeing significant yield losses.

“We have had reports that light leaf spot is now being seen in the field, and so it is vital that growers walk crops and inspect leaves for infection. Or for the avoidance of doubt, utilise the SpotCheck initiative.” 

Highest LLS incidence in Yorkshire


Adam Tidswell, Bayer Commercial Technical Manager for Yorkshire, suggests that the quality of crops in his area is quite varied, depending on proximity to cabbage stem flea beetle hotspots.

“Those crops further away from cabbage stem flea beetle hotspots have grown nicely, but where the pest has been a problem crops are not looking so well and going backwards. That coupled with grazing pigeons means I expect there will be more oilseed rape crop casualties in the spring.

“While I haven’t seen much light leaf spot in commercial crops, there have been exceptions in varieties with poorer Recommended List scores for the disease. Despite this, SpotCheck has clearly indicated that the disease is present across most varieties.”

Mr Tidswell concludes that treating light leaf spot should be amongst growers’ top priorities if they encounter the disease and are able to travel. 

“My advice would be to use Proline (prothioconazole) at 0.46 L/ha when conditions allow. Remember, we rely mainly on protectant activity when it comes to light leaf spot, so the earlier the detection and action the better.”