Scientists have studied a beneficial fungus called Stemphylium sp. Aa22 that lives inside wormwood plants and produces natural insect-repelling compounds called alkyl-resorcinols. By reading the complete genetic code of this fungus, researchers identified the gene responsible for making these compounds and found that growing the fungus in liquid culture produces more of the desired compounds than growing it on solid rice. This research could lead to developing natural, environmentally-friendly pesticides to protect crops from aphids and other pests.