Elm Leafminer Sawfly

Participants in the “Diagnostic Challenge” held during the 2026 Ohio Forest Health in Columbus this past week observed tiny Elm Leafminer Sawfly adults (Fenusa ulmi (= Kaliofenusa ulmi), family Tenthredinidae) bagged in Southwest Ohio. The tiny, shiny-black adults look like gnats on steroids, buzzing around the leaves of their namesake host.

The leaves of elms may be turning brown in southern and central Ohio thanks to the leafmining activity of the Elm Leafminer Sawfly, Fenusa ulmi (= Kaliofenusa ulmi). The sawfly larvae undergo rapid development, so damage occurs quickly.

The leaves of native elms, non-natives, and hybrids can look a bit bedraggled at this time of the year owing to the leafmining activity of the elm leafminer sawfly. Fortunately, leafmining by the sawfly larvae has drawn to a close for the season, so the damage you see now will be the most damage that you'll see this season. Unfortunately, sawfly development has moved past effective control options meaning that you'll have to live with the current damage.