The mild winter and relatively warm weather in April and May have got potato crops off to a good start, but blight poses a threat as conditions become suitable for its sporulation and spread, according to the College of Agriculture, Food and Rural Enterprise (CAFRE).
Already, blight has been identified on some protected crops in the south of Ireland and on several dumps and crops in England.
Adrian Quinn, CAFRE, says when it comes to blight control in crops, fungicide timing and coverage are critical. “No matter how good the product, nothing makes up for a late start, stretched intervals or areas left unprotected. Once blight has got a foot-hold in the crop, it’s almost impossible to eradicate it. Angled nozzles with a medium spray quality give better canopy cover at all stages of growth.”
He said protecting your crop from blight whenever the first blight warning is issued or when plants meet within drills (whichever is earlier), is key to control.
Rapid changes in P. infestans populations causing late blight in Europe, America and Asia, including the emergence of strains which are more aggressive or have reduced fungicide sensitivity have been observed this year.
He said it is good practice to use a range of fungicides with different modes of action and not to rely on any one active ingredient for more than half of the programme. “This makes best use of their different types of activity and reduces the risk of selecting for blight strains resistant to any one fungicide.”