First detection of the Douglas-fir chalcid Megastigmus spermotrophus (Hymenoptera: Megastigmidae) in Patagonia, Argentina

Abstract

The Douglas-fir (Pseudotsuga menziesii) is internationally used for forestry purposes. Nativeto North America, it has been introduced to several areas of the world, including South America, where it is valued for its rapid growth and timber quality. One of its major pests, Megastigmus spermotrophus (Hymenoptera: Megastigmidae) has been described for a major area of Douglas-fir distribution. However, as of this date, no reports of its presence in Central and South America have been made. In this work, we describe the first detection of M. spermotrophus in Argentina, associated to seed orchards in Patagonia. Through X-ray imaging, we found an average infestationrate of 18.7%, which suggests the wasp is already established in the region. We discuss the implications of this finding for Douglas-fir production and propose the emerging need for developing management programs with an emphasis on the local characteristics of the insect-tree dynamics.