Effect of Herbicide Treatment on Leafy Spurge Gall Midge (Spurgia esulae) Population

The Spurgia esulae gall midge was introduced in North Dakota in 1986 as a biocontrol agent for leafy spurge. Spurgia esulae causes stem tip galls thereby decreasing seed production and it has been most successful near wooded areas. However, a second control method is needed to reduce the leafy spurge infestation and prevent spread from roots. Imazethapyr, 2,4-D, or picloram application did reduce the number of S. esulae galls but not the number of larvae per gall. Long-term S. esulae population was not affected by herbicide application. The integration of herbicides with S. esulae would prevent leaf spurge spread from a wooded area and would reduce seed production within an area where herbicides generally cannot be used.