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The Great British climate that creates such wonderful conditions for growing crops is also highly favourable to bacterial diseases. For producers of brassica vegetables, foliar diseases are a constant concern.

As the year nears its end, the mild and wet conditions that characterise an open autumn enable diseases to sporulate rapidly. Such conditions also make protecting crops a challenge as it can be difficult to apply fungicides in a timely and orderly manner while the fluctuating temperatures result in inconsistent growth.

For Cornwall grower Paula George of R&J Kessell Limited near Falmouth, managing disease in the run up to harvest across 400 acres of winter brassicas is central to meeting market specification.

Aside from the difficulties in creating good seedbeds during periods of dry weather and issues with cabbage root fly (Delia radicum) through to aphid control until the onset of winter, disease is the main management concern.

“Disease control in the run up to harvest while observing harvest intervals of typically 14-21 days and ensuring a constant supply of material when growth can be erratic, can be a challenge,” Mrs George says.

Ringspot (Mycosphaerella brassicicola) is a disease of concern because its unsightly lesions can spread rapidly and require only short periods of wetness, typically 3 to 12 hours, and a wide temperature range of 5 to 25oC to infect.

“This season we have used Nativo 75WG (tebuconazole + trifloxystrobin) and the protection it has delivered has been impressive. The greening effect has also been brilliant. Every crop where we have applied Nativo is free of ringspot. It’s been a phenomenal fungicide for us,” Mrs George says.

“We have crops at harvest that were sprayed [with Nativo] four weeks ago. Nine days into harvest these crops remain free of ringspot. We’ve had mild and wet weather too, so it has been tested,” Mrs George adds.

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