DISEASE PREDICTION modelling has revealed that many carrot growers may be leaving Sclerotinia and Alternaria control too late, according to experts.

The traditional timing for Sclerotinia fungicide applications is from mid-July in Lincolnshire to mid-August in Scotland, but in most seasons this is too late, said David Martin of Plantsystems.

Growers need to assess disease risk more accurately in order to give sufficient time for fungicide applications, he said.

“Results of two years’ commercial application of the Plant-Plus model has shown in-field weather and crop data, coupled to the computer model and local weather forecasts, can more accurately predict when Sclerotinia spores are likely to infect growing carrots.”

As a result of using the model, the timing for using protectant fungicides could now be from the end of June, said Moray Coast Produce agronomist, Tim Lyon.

“If we can get the initial Amistar [azoxystrobin] application right, then there’s a good chance of keeping the foliage healthier and greener right through the season” he noted.

The first warning triggers to look for are apothecia on the soil surface and mushroom-like fruiting bodies, added Mr Martin. “There is little or no opportunity to counter Sclerotinia once infection gets into the crop.”

In England Alternaria is a bigger risk for carrots, but disease peaks are more pronounced, which gives growers a good opportunity to vary Amistar applications according to disease pressure, he said.