Abstract <p>The sciarid <i>Bradysia impatiens</i> (Johannsen, 1912) (Diptera, Sciaridae) is known as a polyphagous pest that destroys plants in greenhouses. This species damages more than 25 plant species. The larvae were found on the stems and roots of plants: impatiens plant, Usambara violet (<i>Saintpaulia</i>), snapdragon, bean, <i>Schlumbergera</i>, carnation, chrysanthemum, pelargonium, cucumber, cyclamen, freesia, geranium, hydrangea, lettuce, lily, alfalfa, lupine, corn, melon, peas, poinsettias, potatoes, strawberries, sugar beets, eucalyptus, pine, orchids, and many others. Their activity leads to wilting, stunted growth, chlorosis, premature loss of foliage, and, ultimately, to the death of plants. They also damage champignons and other mushroom crops. The pest has now spread all over the world, so it is not possible to reliably determine its native range. For the first time, a case of damage by <i>B. impatiens</i> larvae to the roots of Sosnowsky’s hogweed <i>Heracleum sosnowskyi</i> Manden. (Apiaceae) has been recorded. More than 100 larvae lived in a root 8 cm thick. The colonization of a dangerous weed by a new pest indicates the ongoing process of interaction between the invasive species and phytophages. A map of the world distribution of the sciarid has been compiled.</p>