Potato crops in Britain are facing high blight pressure this season, demanding the best possible protection under extremely challenging application conditions. Syngenta Technical Manager, Stephen Williams, reported that the BlightCast risk forecasting service has already highlighted high disease pressure for most parts of the UK on repeated occasions through early June.
“The problem for growers has been compounded by high winds and very wet field conditions, which have severely limited application opportunities. Furthermore, with the protracted planting season many growers have crops at widely differing growth stages across the farm, from freshly emerged to flowering. Their blight fungicide selection must be capable of covering as wide a cross section of growth stages,” he added.
Given the season’s high pressure and the increased risk of spore spread on the wind, Mr Williams said growers and agronomists have been seeking guidance on how best to use the four applications of Revus available in the programme.
“They have recognised that when conditions are so severe, it is essential to use the most robust blight programme possible; keeping blight out now will be essential whatever the rest of the season entails. Revus is the top performing fungicide in the Euroblight trials, when products are subjected to the most rigorous testing conditions.”
Based on the trial findings Mr Williams advocates growers start with Revus in the programme from the early rapid canopy stage, and then alternate use with other well-proven performance blight fungicides through to canopy complete. On a weekly spray programme that will cover over eight weeks, or 11 weeks on a 10-day programme.
He added that under high pressure conditions maintaining spray intervals is crucial. Trials have shown that the intrinsically highly active mandipropamid remains effective even at low concentrations, which maintains good levels of protection at the end of the interval, and gives reassuring confidence if subsequent applications are delayed by field conditions.
“Being able to use Revus across a wide range of crop stages keeps things simple. The further advantage in the current conditions is that Revus is extremely rainfast, which is essential to keep protection in place on the leaf with the repeated heavy rain showers. It’s also quick and easy to use, so sprayer operators can cover the largest possible area during available spray windows,” he advised.
The slow start to the potato growing season, with many crops delayed in planting, will mean growers will want to keep crops growing for as long as possible to bulk up at the end of the season, according to Mr Williams. “That makes preventing blight now even more important, to stop spread later in the season. Maintaining clean blight-free foliage is most essential during the tuber initiation and early growth, when they are highly susceptible to infection; using Revus regularly through the programme can help to deliver clean tubers at harvest.”
Herefordshire grower, Giles Edwards, has used Revus for the past three years, targeting protection at rapid growth and canopy complete on crops for the pre-pack market. “It is rainfast and easy to use. We really appreciate the strong performance against blight mid-season,” he said.
It’s a view confirmed by Nick Bragg of Ilminster in Somerset, where he has used Revus for three to four applications per season at rapid growth and canopy complete stages. “It protects new growth, with proven performance. It’s easy to use, and the rainfastness is important when travelling up to 20 miles to spray,” he added.