Macrolabis molesta Dorchin, new species damaging young shoots of commercially grown spineless butcher's broom (Ruscus hypophyllum L.) in Israel is described based on adults, larvae and pupae. Larvae develop gregariously in growing shoots, causing distortion and rotting of the apical meristem, thus rendering affected shoots unsuitable for marketing. This is the first Macrolabis species to be recorded from a monocotyledonous plant. It completes at least one generation a year in fall and early winter, sometimes with an additional generation in spring. Macrolabis molesta has not been detected on the native butcher's broom, R. aculeatus L., thus it may have been introduced into Israel with its host plant in the early 20^th century.