Heavy rainstorms have triggered a series of blight alerts across the UK,from the south west to Scotland. Although pressure has been relatively low thisseason and reduced the inoculum risk, sufficient spores are in the air to havealready hit volunteers and unprotected plants, warned Syngenta TechnicalManager, Mike Welby.
Infection identified in crops this month has highlighted the risk, evenbefore conventional Smith Period warnings had been triggered. Irrigation andhigh humidity in the crop canopy contributes to increased risk, along with moreaggressive blight strains potentially active at lower temperature and humidity,reported Mike.
He advocated growers should now be bolstering more robust treatments intheir mid-season programmes. That must include the most effective foliar blightfungicide, Revus, to mitigate the risk and protect crops from foliar infection.Maintaining a blight free canopy is the primary factor in preventing tuberblight infection as the season progresses, he advised, with developing tubersthrough mid-season the more susceptible to infection.
However, Mike highlighted that many growers applications have beenhindered by strong winds and some heavy rainstorms, which have limited sprayingopportunities.
If application intervals are stretched by spraying delays, its vitalto still have protection in the plant, he pointed out. Revus really is theproduct of choice at this stage, since the active will move into new leafgrowth in the expanding crop canopy, and it remains highly effective even atlow concentrations between applications.
He advised that all growers and agronomistsshould register for the Syngenta BlightCast on-line disease forecastingservice. It provides local five-day forecasts of blight risks that can helpwith improved application timing and product choice. The associated five-dayspray window forecast will also prove invaluable in scheduling and prioritisingtreatments, added Mike.