Red flag raised as risk of potato blight rises again
Rain showers and warming temperatures have heightened the threat of potato blight across the country – with Hutton Criteria disease warnings declared across many of the UK’S key growing regions.
The Blightwatch alert system, hosted by the Agricultural and Horticultural Development Board (AHDB) and the Met Office, hasdisplayedredwarnings since 11 June – the highest level of blight threat – just as many crops are reaching the crucial rapid canopy growth stage.
The AHDB has calculated that controlling the diseases costs potato growers in the UK more than £55 million a year and the Hutton Criteria – which occurs when there are two consecutive days with a minimum temperature of 10C and at least six hours of relative humidity (90 per cent) – has been adopted to give growers warning of the weather conditions likely to prompt an outbreak in their area.
Red alerts have been issued in England for Lincolnshire, Yorkshire, Lancashire, East Anglia and across the West Midlands – and while fewer warnings have been issued in Scotland, growers have been warned to tighten their blight programme, a move especially urgent for growers in Angus and Ayr.
Potato late blight, caused by Phytophthora infestans, has been the major disease of potatoes since its introduction to the UK in 1845 causing losses by destroying foliage and by infectingtubers. Fungicidescontinue to be an important component of late blight control with up to 15-20 applications often being required to control the disease each season.
Commenting on the situation, Corteva Agriscience said that farmers and advisers were well aware that the threat of blight developed quickly in warm, wet weather, particularly with latent blight present in volunteer potatoes from fields that were abandoned following a difficult harvesting campaign in 2019.
The challenge has been intensifying with the widespread presence of newer, more aggressive strains of late blight which made vigilance ever more important.
Corteva’s technical manager for potatoes, Craig Chisholm, said the current situation hadn’t yet reached the epidemic levels of disease seen last June and July when persistent downpours made spray
programmes difficult for many growers.
But he added that the threat to crops was evident and urged potato growers to protect crops now with robust blight prevention programmes.
“The majority of the main crop is just embarking on the rapid growth phase, so the need to be on top of potential blight infection in new growth is key,” he said.
Chisholm said that growers would now be looking for windows of dry, calm weather in which to apply their spray programmes – and advocated a strong preventative strategy which kept the canopy clean as it developed.
He said Corteva’s new blight fungicide co-formulation Zorvec Endavia could play an important role in establishing a clean foundation to any programme.
“Timings will be largely dependent on variety and conditions, but Zorvec offers up to ten days’ protection adding flexibility to programmes at a time when demand on available labour is particularly high.