Cross-kingdom RNA trafficking and environmental RNAi for powerful innovative pre- and post-harvest plant protection

•Small RNAs can transfer from pathogens or parasites into their interacting hosts.•Plant and animal hosts can deliver small RNAs into interacting pathogens and parasites.•External RNAs can be taken up by fungal cells and plant cells and induce RNAi.•Spray-induced gene silencing represents an innovative disease control tool.