Syngenta is urging carrot growers to protect their crops with fungicide before their canopies close, to stave off the risk of Alternaria and Sclerotinia development.

The first Sclerotinia spore germination in carrots was identified in Norfolk last week, although continued dry weather has helped minimise the risk of disease development, according to the company.

However, Adas’s John Birkenshaw has warned that with maincrop carrots progressing well, crops at risk of infection should receive a fungicide treatment before the canopy closes. The wet, warm microclimate beneath the canopy can encourage Sclerotinia and Alternaria to development, particularly in irrigated crops or sheltered and low-lying areas of fields.

“Growers must inspect crops closely at the base of leaves and stems, for early signs of infection,” Birkenshaw said. “Once disease gets into the crop, it is difficult and far more expensive to fix.

“If Alternaria is already active, dose rates must be kept high to achieve control. These treatments should also give some protection against Sclerotinia.”

According to Syngenta’s technical manager Jon Ogborn, pictured below, trials have shown that the company’s carrot fungicide, Amistar Top, can help control Alternaria. The application is made up of difenoconazole and azoxystrobin, which the company claims can provide a two-pronged attack.

In trials, Amistar Top reduced Alternaria infection from 46 per cent in untreated plots to 11 per cent, with an additional 36 per cent increase in control over tebuconazole.

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