Spring clean for OSR leaves over winter

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Oilseed rape crops have, for the most part, come out of the winter remarkably clean of disease after the early intense Phoma pressure was well controlled, reports Syngenta OSDR Manager, Kat Allen (pictured).

Wet and mild weather over the early autumn was positive for crop establishment, but did raise the spectre of early Phoma infection and the risk of rapid development in small plants.

“However, forewarned of attacks, most iOSR growers were ready with Phoma specific treatments and did make timely applications to protect against spots developing. Tracking of disease breaking out by ADAS for the Phoma Alert website highlighted leaf spotting breaking out in the western counties in early October, then moving north and east as the month progressed,” said Kat.

Under intense pressure varietal susceptibility brought a few days grace, but infection soon spread across all sites and crops.

Now that older infected leaves have been shed and drier weather conditions in early December, particularly across the eastern counties, for the most part crops had remained remarkably free from new Phoma outbreaks.

Furthermore, whilst there was talk of early Light Leaf Spot infection, the disease had not appeared to have developed to any great extent into December.

Even collecting and incubating leaves in conditions conducive to LLS had failed to identify any great infection.

In recent years, ADAS trials and Syngenta research has shown that damaging LLS infection has typically not arrived until post-Christmas and into the New Year. Into January this year crops looked remarkably clean and green

That has been good news for growers seeking to hold down autumn input costs, enabling them to focus primarily on Phoma with Plover treatments in the autumn, and possibly adding a cost-effective tebuconazole with later applications in higher risk LLS areas.

This strategy has also retained the option for limited and more expensive prothiaconazole-based fungicide treatments for use in the spring, if required.

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