Scientists discovered that a liquid extract from Cinchona bark, which contains quinine, can effectively kill a fungus that damages rice crops. The treatment works by blocking the fungus’s ability to absorb tryptophan (an important amino acid) and damaging its energy-producing mitochondria. When tryptophan was added back to the treatment, the fungus recovered, confirming this is the main way the extract works. This natural, plant-based approach could provide an eco-friendly alternative to chemical fungicides while reducing the risk of the fungus developing resistance.