Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist
Large numbers of very small, about 1/16th inch long, pinkish worms were found during mid April under elm trees. Looking like grains of rice, these 'worms' are actually a type of fly known as a gall midge. It is not clear what species is present but they appear to attack the developing samaras (winged seeds) in early spring. Later in the spring (sometime in April to early May), the mature larvae drop to the ground where they remain until the next spring. The galls are harmless to the tree and no control is necessary. The larvae can be a nuisance when they fall on driveways or sidewalks. The only necessary step is sweep them off. This is a short lived problem that will go away on their own.