Population dynamics of the northern tamarisk beetle (Diorhabda carinulata) in the Colorado River Basin

Open-File Report 2018-1070
By:  and 



Throughout the Southwestern United States, riparian systems contain narrow belts of vegetation along streams and rivers. Although only a small percentage of the total land cover, this ecosystem is important for maintaining high species diversity and population densities of birds. Anthropogenic changes to Western riverine systems have enhanced their susceptibility to invasion by introduced plant species, in particular, ornamental plants from the genus Tamarix (or saltcedar), which can establish itself in dry, salty conditions and spread rapidly. Recently, the central Asian saltcedar leaf beetle (Diorhabda carinulata) was released as a biocontrol for tamarisk. Since its release on the Colorado Plateau, tamarisk beetle populations in Nevada, Utah, Colorado, and Wyoming have widely expanded, leading to widespread tamarisk defoliation, and concerns from land managers regarding the consequences of the environmental impact. Defoliation can also negatively impact avian communities in the short term by decreasing insect abundance and nesting success, owing to increased solar radiation or loss of camouflage. 

This report details two studies that examine the spread of the introduced tamarisk beetle over parts of the Southwestern United States. The first chapter documents plant phenology and beetle abundance and movement along the Dolores and San Juan Rivers, two major tributaries of the Colorado River. This study demonstrates that D. carinulata population-movement patterns can be highly influenced by the availability of beetle food resources and that local beetle “boom and bust” events are common. The second study demonstrates that the extent and timing of tamarisk defoliation are predictable on the basis of (1) abiotic cues for D. carinulata activity, (2) spatial distributions and abundances of D. carinulata across a site, and (3) movement of D. carinulata as a result of available tamarisk foliage. A significant positive correlation exists between the spatial distributions of D. carinulata populations in the fall and those of the first generation of larvae in the following spring, suggesting that the extent of tamarisk defoliation as a result of abundant larval populations is predictable. The results of these two studies will enable conservationists to better understand the variable timing of tamarisk defoliation events across a landscape and provide a template to forecast tamarisk defoliation levels and rates in areas that have yet to be colonized by D. carinulata.

Suggested Citation

Jamison, L.R., and van Riper, C., III, 2018, Population dynamics of the northern tamarisk beetle (Diorhabda carinulata) in the Colorado River Basin: U.S. Geological Survey Open-File Report 2018–1070, 67 p., https://doi.org/10.3133/ofr20181070.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

Publication type Report
Publication Subtype USGS Numbered Series
Title Population dynamics of the northern tamarisk beetle (Diorhabda carinulata) in the Colorado River Basin
Series title Open-File Report
Series number 2018-1070
DOI 10.3133/ofr20181070
Year Published 2018
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Southwest Biological Science Center
Description iv, 67 p.
Country United States
State Colorado, Utah
Other Geospatial Dolores River, San Juan River
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details