Potato crops are at high risk of early attacks of blight this season, if weather conditions remain conducive to infection, warns Syngenta potato specialist, Rob Farrow. As soon as temperatures rise the risk will increase in any wet periods, but growers and agronomists can be effectively forewarned and take appropriate action thanks to the Syngenta BlightCast system.
Now available free on-line, it will give potato growers and agronomists a five-day advance warning of localised blight risks. BlightCast has been developed to enable risk based selection of appropriate fungicides and ensure application at the right time to prevent infection.
Mr Farrow highlighted that the increased incidence of blight after an incredibly difficult season last year has left a legacy of potential infection sources from discard dumps, volunteers and seed. Furthermore, the cold soils and slow start to growth after planting this year means that most crops are now emerging at the same time and with simultaneous exposure to risk; that could further stretch growers capability to maintain appropriate blight control programmes through the season.
He reported that BlightCast has been activated early this year to aide spray timing and product selection from the start of the season. He pointed out that whilst conditions remain cool during the early stages of establishment, there is a greater risk of infection from blight zoospores and their motility through soil moisture, where growers and agronomists should be focusing on Shirlan for initial TO applications.
Once crops are growing through the rapid canopy development phase, Mr Farrow advocated the use of Revus when BlightCast indicates risk of disease attack. The positive movement of mandipropamid across the expanding leaf area offers highly effective protection against infection, which makes Revus the leading foliar blight fungicide in the Euroblight listings.
BlightCast calculation of conditions conducive to blight are also invaluable for helping make proactive agronomy decisions, such as when to include a cymoxonil tank-mix for additional kick-back activity, or assessing how to cope with more aggressive strains of blight that could be active at lower temperatures, he added.
In the past growers have relied on weather records indicating Smith Periods when blight risk had already occurred. That was after the event, and when it was too late to make preventative applications, said Mr Farrow.
Now we have the technology and capability to forecast when conditions conducive to blight are likely to occur, and give growers the chance to take positive action to minimise the risk of infection. BlightCast has proven to be extremely valuable and reliable over the past four years.