The Larch Casebearer in the Intermountain Northwest

Abstract

The larch casebearer, Coleophora laricella Hubner (Lepidoptera: Coleophoridae), is a small silver-gray moth whose larvae mine needles of larches, Larix spp. Apparently of European origin, this defoliator was first recorded in North America near Northampton, Massachussetts, in 1886.³ It had spread westward to Minneapolis by 1950¹² and, in the spring of 1957, was collected just south of St. Manes, Idaho. A survey of larch forests in the intermountain region that year indicated that about 44,000 ha (170 sq mi) were infested.¹ The population spread rapidly and uniformly until, in 1970, it occupied virtually all larch stands in the intermountain regions of eastern Washington, Oregon, and northern Idaho (Fig. 1).