In: Van Driesche, R. G.; Winston, R. L.; Perring, T. M. ; Lopez, V. M., eds. Contributions of Classical Biological Control to the U.S. Food Security, Forestry, and Biodiversity. FHAAST-2019-05. Morgantown, WV: U.S. Department of Agriculture, Forest Service. p. 329-355.
The biological control program against Tamarix spp. (tamarisk/saltcedar; Tamaricaceae) was initiated in the 1970s to reduce negative impacts of this invasive Old World shrub to riparian biodiversity and ecosystem function in western North America. Field releases of host-specific leaf beetles (Chrysomelidae) in the genus Diorhabda were initiated in 2001, with significant establishment and widespread defoliation observed roughly two years after open releases. What followed were a variety of complex interactions among invasive Tamarix, its guild of herbivores including Diorhabda spp., and the physical and biotic environment, which varied across the western U.S. project area. Defoliation yielded sustained lower evapotranspiration and opened canopies, allowing increases in desired vegetation in some areas, while in other areas beetle establishment failed for reasons that included less-suitable host species, mismatches of environmental cues with diapause development of the beetle, and predation by generalist insectivores. In some regions, such as Texas, agent populations were short-lived, resulting in lack of sustained Tamarix suppression. In other areas, beetle populations reached initial epidemic densities but then declined to moderate levels with patchy subsequent defoliation and diminished target mortality. These short-term dramatic impacts to invasive Tamarix, but limited sustained control, suggest potential value in releasing additional host-specific agents, some of which have already been studied and readied for petitioning for release.
Gaffke, Alexander M.; Dudley, Tom L.; Bean, Daniel W.; Drus, Gail M.; Johnson, Matthew J.; Knutson, Allen E.; Weaver, David K.; Sing, Sharlene E.; Orr, Bruce K.; Thompson, David C. 2022. Tamarix biological control in North America [Chapter 28]. In: Van Driesche, R. G.; Winston, R. L.; Perring, T. M. ; Lopez, V. M., eds. Contributions of Classical Biological Control to the U.S. Food Security, Forestry, and Biodiversity. FHAAST-2019-05. Morgantown, WV: U.S. Department of Agriculture, Forest Service. p. 329-355.