Copper in plant protection: current situation and prospects

Abstract

Copper has been used in agriculture to control oomycetes, fungi and bacteria for over a century. It plays important roles in integrated pest management, but is essential in organic farming, where disease management depends almost exclusively on its use. However, the use of this heavy metal may have log-term consequences due to its accumulation in the soil, which appears incompatible with organic farming’s objectives. This awareness led the European Union to establish maximum limits on copper in organic farming since 2002 (Commission Regulation 473/2002), and further decisions on its use in crop protection are to be taken soon. At present, copper compounds are approved as plant protection products until 31 January 2019. This review examines the current state of copper use, the regulatory framework, and limits set for copper in organic farming. Strategies to reduce copper inputs are also considered, including: preventive phytosanitary measures, innovative formulations with reduced copper content, optimization of copper dosages, the use of forecasting models, the use of resistant varieties, optimization of agriculture management, and natural alternatives to copper-based products. This review also examines the main research projects exploring farming practices and appropriate alternatives to copper use for the control of plant pathogens. The review highlights that, while there is currently no replacement for this heavy metal having the same plant protection effectiveness, agronomic measures and management practices can be combined to reduce the amounts of copper used for this purpose.