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Title: Leaf beetles lasso tamarisk without hurting the relatives in Texas and the Southwest USA

item Moran, Patrick
item Deloach Jr, Culver
item KNUTSON, ALLEN - Texas Agricultural Extension Service

Submitted to: Biocontrol News and Information
Publication Type: Trade Journal
Publication Acceptance Date: 8/16/2009
Publication Date: 9/1/2009
Citation: Moran, P.J., Deloach Jr, C.J., Knutson, A. E. 2009. Leaf beetles lasso tamarisk without hurting the relatives in Texas and the Southwest USA. Biocontrol News and Information. 30(3):50N-52N.

Interpretive Summary: Interpretive Summary not required for Trade Journal.

Technical Abstract: This online trade journal article summarizes recent progress in biological control of tamarisks (Tamarix spp., Tamaricaceae) in North America. Tamarisks are a group of five exotic Eurasian shrub/tree species plus hybrids (also known collectively as saltcedar) that have invaded over 1 million hectares of riparian and rangeland habitats from Montana to central Mexico and westward to the Pacific. Biological control of tamarisks began in 2001 in the western U.S., including Nevada, Utah, and Colorado with the release of a leaf-feeding beetle from China (known at the time as Diorhabda elongata deserticola, now known as D. carinulata). The beetles have since defoliated over 50,000 hectares of saltcedar. Other populations of the beetle, which are better-adapted climatically to the southwestern U.S., Texas, and Mexico, were released in the field in 2003-2004. A beetle from Crete, Greece (now known as D. elongata), has established a large, defoliating population that has dispersed over 25 km in saltcedar tamarisk near Big Spring, Texas as of 2009, and has also established populations at sites along the Upper Colorado and Pecos Rivers in Texas. This beetle, as well as a species collected from Uzbekistan in Asia Minor (D. carinata) and from Tunisia in North Africa (D. sublineata), are being evaluated in field releases at many sites along the Rio Grande, using improved release methods and including native plant and wildlife monitoring. Dalogue between the U.S. and Mexico, as well as with landowners and natural resources managers in the U.S., has been facilitated by field days and binational meetings. A 2009 taxonomic monograph has defined five species of Diorhabda tamarisk beetles, four of which have been released in North America. This work also modeled the climatic suitability of the four species, yielding predictions about the regions in which each species is most likely to establish on tamarisks. Another major recent issue concerns the ability of the tamarisk beetles to feed on athel (Tamarix aphylla), a close relative of the saltcedar tamarisks. Athel is exotic, and is invasive in some areas, but it is used as a shade and windbreak tree in Mexico and to some extent in the southwestern U.S. There are six North American species of shrubs and herbs in the genus Frankenia, the closest native genus to tamarisks; Frankenia is in a closely-related plant family (Frankeniaceae, Order Tamaricales). Previous lab and field cage tests had shown that tamarisk beetles can feed and develop on athel, and to a lesser extent on some Frankenia species. Newly-published results from open field tests showed that tamarisk beetles lay 2.5-10-fold more eggs on saltcedar tamarisks than on athel, and lay almost no eggs and cause no damage to Frankenia spp. The recent research results and successful field releases demonstrate the potential impacts and benefits of the biological control program for tamarisks.