Alternative Plant Protection Products and Fertilisers for Organic Farming

Organic farming is dependent on the use of externally produced pesticides. Often, copper-based pesticides are used here, while in the Mediterranean region they are also mineral oil-based. However, their use is controversial. The European research project RELACS is looking for alternatives.

Copper is indispensable for organic farming because of its effectiveness against various harmful fungi, for example in viticulture and the cultivation of fruit and potatoes. The copper ions in the active ingredients penetrate the fungal cells and prevent vital enzyme reactions. According to, researchers at the Julius Kühn Institute (JKI) assume that a complete discontinuation of the use of copper-based pesticides would lead to a harvest failure of 40 to 80 percent, depending on the crop and weather conditions.

Neverteless, their use is controversial, as copper is a heavy metal that is deposited particularly in upper soil layers and does not degrade. Because copper is toxic not only to harmful fungi but also to other microorganisms, it can change soil life and thus soil composition. For this reason, finding alternatives to copper is one of the research priorities of the European research project RELACS (Replacement of Contentious Inputs in Organic Farming Systems), whose aim is to reduce the use of externally produced materials in organic farming.

Combination of complementary approaches: plant extracts and physical methods

Another focus of the project, which is based at the Research Institute for Organic Agriculture (FiBL) in Switzerland and cooperates with 15 partner institutions and organisations, are alternative methods to control mealybugs, red Californian red scale and Aleurocanthus spiniferus (spiny whitefly), which are the main pests in citrus fruit cultivation and are conventionally controlled with mineral oil derivatives. For example, the Fondazione Edmund Mach in Italy is researching the effectiveness of a combination of plant extracts and physical methods. Specifically, it is investigating the use of the essential oil of Sweet Orange and the extract of Blue Clitoris in combination with a vibration device. The latter is intended to use vibration to disrupt the mating behaviour of the pests, while the plant products promise a deterrent effect.

Recycled fertilizers

RELACS is also investigating the potential of alternative fertilizers such as recycled human waste from urban wastewater streams. To this end, the researchers analysed the nutrient values of 79 farms in seven EU regions. The result showed an average surplus of nitrogen (+28 kgN/ha) and an almost balanced phosphorus (1 kgP/ha) and potassium (+2 kgK/ha) balance.

However, the nutrient contents varied greatly between farms (e.g. -15 to +40 kgP/ha for phosphorus). Farms with external nitrogen input tended to show surpluses of all three nutrients, while the increasing reliance on biological nitrogen fixation induced more negative budgets of phosphorus and potassium. The survey of farmers showed that all of them would be open to the use of recycled fertilisers, including from urban waste water. However, they had concerns about contamination and customer acceptance.