SUITABILITY OF DIORHABDA ELONGATA (COLEOPTERA: CHRYSOMELIDAE) FOR BIOLOGICAL CONTROL OF SALTCEDARS (TAMARIX SPP.) IN THE SOUTHERN UNITED STATES AND NORTHERN MEXICO

Authors: Milbrath, Lindsey; Herr, John; KNUTSON, ALLEN - TEXAS A&M UNIVERSITY; Tracy, James; BEAN, DAN - 5325-43-00; RODRIGUEZ-DEL-BOSQUE, LUIS - INSTITUTO NACIONAL FOREST; Carruthers, Raymond; Deloach Jr, Culver

Submitted to: Proceedings of National Congress of Biological Control
Publication Type: Proceedings
Publication Acceptance Date: 11/14/2003
Publication Date: 1/10/2004
Citation: Milbrath, L.R., Herr, J.C., Knutson, A.E., Tracy, J.L., Bean, D.W., Rodriguez-del-Bosque, L.A., Carruthers, R.I., Deloach, C.J. 2003. Suitability of Diorhabda elongata (Coleoptera: Chrysomelidae) for biological control of saltcedars (Tamarix spp.) in the southern United States and northern Mexico. In: Memoirs of the XXVI Congresso Nacional de Control Biologico, November 3-8, 2003, Guadalajara, Jalisco, Mexico. p. 225-227.

Interpretive Summary: Saltcedars are exotic shrubs or trees that have invaded river systems throughout the Western U.S. and northern Mexico, causing major problems. The importation of insects from the Old World that damage saltcedar, but not other plants, has good potential to control saltcedar. A leaf-feeding beetle, released and now established in northern areas of the U.S., appears very promising in controlling saltcedar. Other populations of the beetle have been studied that we anticipate will establish in the southern U.S. and northern Mexico and cause significant damage to saltcedar. Control of saltcedar will improve native plant communities and wildlife habitat, and insure water supplies for agriculture and municipalities.

Technical Abstract: Populations of the leaf beetle, Diorhabda elongata (Coleoptera: Chrysomelidae) from Fukang, China and Chilik, Kazakhstan were released into the open field in May 2001 in the United States at 5 release sites north of the 38th parallel and initially appear to be achieving successful biological control of saltcedar (Tamarix spp.). However, these beetles have not established at 4 more southern release sites - Seymour in northern Texas and at Bishop, Hunter-Liggett and Cache Creek in central California - probably because daylength in these southern areas is too short. Laboratory tests demonstrated that beetles from Fukang, China require 14 hr 45 min daylength to avoid entering premature overwintering diapause. However, maximum summer daylength at Seymour, TX is only 14 hr 20 min, is only 14 hr 10 min at Temple, TX, and is even less further south. This causes the beetles to enter diapause in early July and they probably starve before food becomes available the following March. Thus, these beetles cannot control damaging stands of saltcedar from southern California to Texas and in northern Mexico. Additional studies demonstrated that populations of D. elongata from Crete, Greece; Sfax, Tunisia; Karshi, Uzbekistan; and Turpan, China are more adapted to short daylengths. These beetles may be able to establish in the area from the 38th parallel south into northern Mexico.