Syngenta Oilseed Rape Field Technical Manager, Simon Roberts, warned that even in well-established crops, any new infection on recently emerged leaves could quickly move down the petiole and into the stem - which would lead to yield robbing cankers next spring.  “Those crops showing early signs of spotting on small leaves will be a priority for PLOVER treatment,” he advised.

         

“Infection spots on older, larger leaves will take longer to spread down to the stem, which gives growers some extra flexibility in spray timing. But they will still require treatment where more than 10% of plants are showing any signs of Phoma leaf spotting.” Warm weather and wet leaf surfaces would increase the speed at which the disease spreads down to the stem, he added.

Mr Roberts advocated growers should also consider their varieties’ Phoma susceptibility in scheduling PLOVER applications to prevent damage. “Anything with a resistance rating of six or less must be considered particularly at risk, especially from early disease infection. They are also more likely to require two-spray programmes this season to prevent later infection.

“High ratings for Phoma resistance could help slow the disease development, but it does not confer protection and they will still need at least one treatment when thresholds are reached.” A two-spray PLOVER programme in the autumn has proven to produce the highest returns in most seasons, especially if milder, open conditions prolong infection periods.

PLOVER applications now could also have an effect in reducing infection pressure of Light Leaf Spot as the season progresses, said Mr Roberts, as well as retaining growers’ options for prothioconazole treatments where required in the spring.

“Phoma remains the most damaging disease of oilseed rape in terms of overall yield loss. Whilst it has been one of the best seasons for oilseed rape establishment for many years, preventing Phoma infection now will be crucial enable crops to reach their full potential.”