In the Netherlands copper is not allowed as a fungicide, but it is allowed as foliar fertiliser. A national rule is also that the potato vine should be killed/burned when 5% of the foliage is infected
by late blight.
After a dramatic late blight year in 2016 and much negative press, the Dutch organic sector has decided to transition to a copper free potato production in 2020 and will promote the
use of late blight resistant potato cultivars. An integrated plan is designed for a chain wide approach including commitment of breeders, farmers and retailers.
The expectation is that in 2020 some ten to twelve resistant cultivars will be available. The first generation resistant cultivars will have one major gene, but there are already five different resistance genes available for commercial cultivars.
The organic breeding programme Bioimpuls (2009-2019) is a collaboration of Louis Bolk Institute, Wageningen University, six commercial breeding companies and ten farmer breeders; it includes a prebreeding programme with ten different sources of late blight resistance, aimed at combining R genes to increase the durability of the resistance.
Selection is supported with molecular markers. However, the first cultivars with stacked R genes will only become available in at least five years’ time. Therefore, an important task for the transition period is training farmers in resistance management to avoid resistance breakdown and establishment of late blight physios.
