BIOLOGICAL CONTROL PROGRAMS FOR INTEGRATED INVASIVE PLANT MANAGEMENT

Authors: Deloach Jr, Culver; Carruthers, Raymond

Submitted to: Weed Science Society of America Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/5/2004
Publication Date: 3/1/2004
Citation: Deloach, C.J., Carruthers, R.I. 2004. Biological control programs for integrated invasive plant management. In: Proceedings of Weed Science Society of America Meeting. Kansas City, MO: Weed Science Society of America. 2004 CDROM.

Interpretive Summary: Biological control of exotic, invasive weeds of rangelands and natural areas, by the introduction of insects or plant pathogens from the original homeland of the weeds, has been used against 133 weeds in 51 countries since 1865, and against 40 weeds in the United States since 1945. Biological control recently has been applied to saltcedar. Saltcedars (Tamarix spp.), exotic shrubs or small trees from Asia and the Mediterranean area, have invaded western U.S. river bottoms and lakeshores since the 1920s where they cause great environmental damage and great losses of water critically needed for native ecosystems and for agriculture and municipalities. Of the 300+ insect species that attack saltcedars in their homeland, one insect, the leaf beetle Diorhabda elongata from China and Kazakhstan, was tested intensively over a 10-year period in quarantine at Temple, TX and Albany, CA and released into field cages at 10 sites in 6 western states during the summer of 1999 and into the open field in May 2001. By September 2003, the beetle had completely defoliated between 15 and 500 acres of saltcedar at each of 5 sites north of the 37th parallel, but did not overwinter or establish in more southern areas. In 2001 and 2003, different biotypes of this beetle were found in Crete, Tunisia, Uzbekistan and China that can overwinter in more southern areas. The Crete biotype was tested and released into the open field at 5 sites in Texas, 1 in New Mexico and 1 in California during late summer of 2003 and spring of 2004 where it overwintered and vigorously attacked saltcedar during the spring of 2004. Our results indicate that biological control has a high probability of providing good control of saltcedars over much of the infested area in the U.S.

Technical Abstract: Biological control of weeds has been used worldwide since 1865 against more than 133 weed species in 51 countries. In the United States it has been used since 1945 against some 40 weeds, with about one-third completely or substantially and one-third partially controlled. Most success has been achieved with exotic, invasive broad-leaved or woody weeds of rangelands and natural areas, using the 'classical' approach of introducing the insects or plant pathogens that control the weed in its homeland. We use saltcedars (Tamarix spp.) as an example. Saltcedars are shrubs or small trees that were introduced into the United States from Asia and the Mediterranean area, beginning in 1823 as ornamentals and to control streambank erosion in the West. Since the 1920s, they have rapidly invaded western riparian areas where they displace native plant communities, degrade wildlife habitat (including that of some 40 threatened or endangered species), use great quantities of scarce groundwater and stream flow needed for agriculture, municipalities and the environment, increase wildfires and soil salinity, and reduce recreational usage. Since 1991, our overseas cooperators in Israel, Kazakhstan, China, France and Turkmenistan have identified over 300 insect species that damage saltcedars but not other plants. We have tested several of these at ARS laboratories in Temple, TX and Albany, CA. We released the first of these, a leaf beetle, Diorhabda elongata from Kazakhstan and China, into field cages at 10 sites in 6 western states in 1999 and into the open field in May 2001. By the end of the third growing season (September 2003) they had completely defoliated 500 acres of saltcedar at Lovelock, NV; 30 acres at Schurz, NV; 100 acres at Delta, UT; 100 acres at Pueblo, CO; and 15 acres at Lovell, WY, all sites north of the 37th parallel. During 2003, they also were released in Montana and Oregon. These Fukang/Chilik beetles did not overwinter or establish south of the 37th parallel because the short summer daylength there caused premature diapause. However, one of us (Carruthers) and our overseas cooperators found different biotypes of these beetles in Crete, Tunisia, Uzbekistan and China that overwinter successfully in the southern areas. Beetles from Crete overwintered successfully in field cages at Temple, Dallas, Big Spring, and Kingsville, TX; and Artesia, NM and vigorously attacked saltcedar during the following spring. They were released into the open field at 6 sites in Texas; at Artesia, NM; and near Woodland, CA during the fall of 2003 and the spring of 2004.