Editorial Special Issue: 'Algae and cyanobacteria: prospects and challenges for plant disease management'

The use of alternatives to synthetic products is recommended by the European Regulation No. 1107/2009 by placing plant protection products on the market and repealing Council Directives 79/117/EEC and 91/414/EEC. Indeed, the use of synthetic products has been restricted due to their impact on the environment and on human and animal health. In addition, a number of initiatives have recently been implemented at the European level within the ‘Green Deal’ that aims towards a green transition to contrast climate change and preserve the environment. One of the objectives of the ‘Green Deal’ is to reduce by 50% the use and risks of chemical pesticides in agriculture by 2030 that may lead to a more problematic management of plant pathogens. A new challenge for research is to reveal novel alternatives to chemical pesticides, such as algae and cyanobacteria since they are a source of many bioactive compounds. The Special Issue “Algae and cyanobacteria: prospects and challenges for plant disease management” includes six research articles (Table 1) and three reviews providing innovative results on the potential of algae and cyanobacteria as useful tools for plant disease management. The research articles include studies both in vitro and in planta by using algae and cyanobacteria applied through different methods.