Prepare a resistance management strategy for your potatoes
“Failure to prepare is to prepare for failure” is an often quoted business maxim, but as far as managing potato blight is concerned, the saying holds a valuable truth, says Dr. Dominic Lamb, UK and Ireland Business Manager for Gowan.
Following four consecutive wet summers, of which 2012 was by far the worst, the potential for potato blight inoculum from discard heaps and volunteers is very high and already blight out breaks have been reported. This should signal the need to prepare a strong, robust blight control programme, incorporating a strong anti-resistance strategy.
In order to protect existing fungicides and maintain their efficacy, especially in the light of more aggressive blight populations and new strains that are resistant to leading blight fungicides, it is vital that growers and advisors build strong anti-resistance strategies into their programmes, says Dominic Lamb. “I always advise growers to integrate fungicides with different modes of action and those with multi-site activity. This way blight is effectively controlled and it ensures that individual fungicides are not put under too much pressure. We must use the existing range of available products wisely because new active substances with new modes of action are very few and far between.”
He explains that, although there are many brands of late blight fungicides, there are fewer active ingredients and even fewer ways in which these actives actually work on the blight pathogen. Focusing on the actual sites of action for blight fungicides, as defined by FRAC, single-site fungicides can be classified into just five groups. “In other words you really have just 5 specific tools to play with in the blight tool box. With such a limited choice, it makes sense to integrate a number of fungicides, including the unique acting Electis, into every programme. If you don’t use zoxium, you are automatically eliminating one of the five sites of action, a very limiting strategy when it comes to resistance management,” explains Dr. Lamb.
Dr. Lamb points out that Electis 75 WG contains two active substances, zoxium® and mancozeb from two different chemical groups and that it provides a unique benefit in potato blight resistance management. “There is no known resistance to Electis and no shift in its status. Acting on at least 6 different sites within the blight pathogen, multisite mancozeb has shown no signs of resistance for over half a century! The low resistance risk of Electis is proven by its label, allowing up to eight sprays in any one season, although obviously Gowan would not recommend such an approach! It controls all blight races and strains, including the new genotypes and those resistant to phenylamides.”
“When it comes to managing blight resistance and controlling different blight strains, we are entering an era of integrated approach that requires growers to rotate modes of action and chemical families - Electis is an essential player, representing one out of the five major sites of action. By including this active in the blight programme, growers take advantage of all available sites of action and minimise any future risk,” he says.
Dr. Lamb goes on to say, “In order to get maximum benefits, apply Electis at full canopy, before blight is present in the crop, and thereafter at 7 day intervals depending on blight risk. Every season is a challenging season for the potato crop and I strongly advise growers to prepare a robust blight programme and include at least one application of Electis in that programme.”
“Although not on the label here in the UK, Electis rated 2.5 stars out of three by the European Euroblight panel of experts on Alternaria control – the highest rating for any dual-control product that controls both late and early blight. The only products to receive the maximum 3 star rating are strobilurins whIch offer no late blight control. The same experts rate Electis as comparable with well-known products such as Shirlan and Invader for late blight control” says Dominic.
