The retardation of growth of apple stock in Iowa nurseries, caused by the apple leaf-hopper, has been very common from year to year, and has resulted occasionally in extensive losses to young nursery stock. The large nurseries at Charles City, Des Moines, and Shenandoah, as well as many others in the state, are more or less troubled with this insect every year. Although this leaf-hopper attacks many kinds of plants and trees, the injury is most serious on young apple trees, especially when planted in the nursery row, and it is as a nursery pest that this insect is considered in this bulletin. During the past year the apple leaf-hopper was more abundant than common, and as a result a large amount of nursery stock was stunted seriously. Aside from apple trees this insect frequently attacks birch and Norway maple trees, and even potatoes. The pest is known to science as Empoasca mail.