Crop-specific copper applications by Swiss organic farmers

There are currently quantitative restrictions on the use of copper-based fungicides. In Switzerland, restrictions are imposed on organic farmers by the licensing authority for pesticides, the Swiss Organic Farming Ordinance and the Bio Suisse Standards. The maximum permitted quantities are 1.5 kg/ ha/a in pome fruit, 2 kg/ha/a in soft fruit and 4 kg/ha/a in other crops. We have examined the actual quantities of copper applied on farms. For this study, we surveyed Bio Suisse producers on their use of copper-based fungicides in the years 2009–2012 and extrapolated the average quantities of copper applied on crop rotation plots and viticulture plots. Average copper applications were less than 1 kg/ha/a in apples, all soft fruit species, cabbages, tomatoes, cucumbers and resistant grape cultivars. Between 1 and 2 kg/ha/a were applied to pears, apricots and carrots, whereas cherries, potatoes, celeriac and traditional European grape cultivars received more than 2 kg/ha/a. Copper was applied at average rates of 0.7 kg/ha/a in crop rotation plots and 2.5 kg/ha/a in viticulture plots. This survey shows that Swiss organic farmers apply significantly less copper than the maximum permitted quantities. The organic farming sector is pursuing a combined strategy for minimizing copper applications that involves resistant cultivars, adaptations in crop husbandry, optimized copper applications and the use of alternative products.