Resumo. Delia Robineau-Desvoidy, composed of flies popularly known as root maggot flies, is a diverse genus with unclear delimitation. It comprises polyphagous species and some important agricultural pests. Delia sanctijacobi (Bigot) is native to South America, occurring in Argentina, Brazil, Chile, Peru, and Uruguay; the larvae are commonly known as “potato worms” and have been misidentified as Delia platura (Meigen) in Brazil. Delia sanctijacobi attacks the seeds and seedlings of several plants of commercial importance. We present new geographic records of D. sanctijacobi in Brazil and describe the damage caused by their larvae on commercial bean and onion in Paraná and Santa Catarina between 2019-2022. Delia Robineau-Desvoidy, composed of flies popularly known as root maggot flies, is a diverse genus with unclear delimitation. It comprises polyphagous species and some important agricultural pests. Delia sanctijacobi (Bigot) is native to South America, occurring in Argentina, Brazil, Chile, Peru, and Uruguay; the larvae are commonly known as “potato worms” and have been misidentified as Delia platura (Meigen) in Brazil. Delia sanctijacobi attacks the seeds and seedlings of several plants of commercial importance. We present new geographic records of D. sanctijacobi in Brazil and describe the damage caused by their larvae on commercial bean and onion in Paraná and Santa Catarina between 2019-2022.