A field survey was conducted to seek potential biological control agents of Imperata cylindrica (L.) Beauv. (Poaceae), which was introduced from Japan and the Philippines into the southeastern USA, and became a highly serious weed there. Lepidopteran larvae were discovered boring in the basal stems of I. cylindrica in Itoshima city, Fukuoka Prefecture, Kyushu, Japan in 2013. Adults reared from these larvae were identified as Acrapex azumai Sugi (Lepidoptera: Noctuidae). This is the first host record for A. azumai. Sequencing of the COI (cytochrome oxidase I) gene revealed significant similarity to other Acrapex spp., for which comparative sequence data is available. Acrapex azumai may have potential as a biological control agent of I. cylindrica in the southeastern USA.