Dispersal and Distribution of Biological Control Agents for Lythrum Salicaria in Indiana

Abstract

The invasive wetland perennial, Lythrum salicaria has spread throughout Indiana wetlands since 1900. Four insect species were approved for release as biological control agents. These species included: Hylobius transversovittatus, Nanophyes marmoratus, Galerucella calmariensis, and G. pusilla. The distribution of these beetles has been monitored by the Indiana Department of Natural Resources since 1994. This project aimed to develop an updatable GIS database, expand the existing data on locations of these control agents, and estimate their distribution throughout the state. Nanophyes marmoratus and Hylobius transversovittatus have spread slowly between wetlands, which limited the analysis of this work to the spread of Galerucella. Geospatial analyses of Galerucella spp. indicates that they have become widely distributed in the northern region of the state. By calculating distances and date of initial observation between sites, it was estimated that Galerucella spp. spread at a rate of least 491 meters per year with a maximum rate of 1,822 m/yr. This simplified calculation of dispersal rates and GIS mapping allows for visualization of areas for potential future releases in order to maximize the control of L. salicaria. Additionally, it suggests that Galerucella spp. have become widely established in northern Indiana.