Landscape - Birch Leafminer

The following is information on Birch Leafminer, an insect pest active at this time.

Birch Leafminer

The insect that causes the splotch mine that shows up on birch in June is a sawfly larva that feeds between the leaf surfaces. The insect has been overwintering in the soil in the pupal stage. The adults start to emerge around 190 degree days – about when redbud is in full bloom. In Delaware we are beyond this point. The adult females will oviposit in new foliage of birch trees. The damage will show up as brown leaf blotches which will be very evident in June.

Control: If your customer is tolerant of a little foliar injury then I would do nothing for this pest. The plants are not really damaged unless the infestation is excessive. If control is needed then a soil application of imidacloprid or dinotefuran would control leafminers. This application would also take care of aphids that will feed on birch this summer.

Birch leafminer damage. Photo by Brian Kunkel, University of Delaware, Bugwood.org.

Information from the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension