|Deloach Jr, Culver|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2002
Publication Date: 5/1/2003
Citation: Lewis, P.A., DeLoach, C.J., Knutson, A.E., Tracy, J.L., Robbins, T.O. Biology of Diorhabda elongata deserticola (Coleoptera: Chrysomelidae), an Asian leaf beetle for biological control of saltcedars (Tamarix spp.) in the United States. Biological Control. 2003. v. 27. p. 101-116. Interpretive Summary: Saltcedar is an exotic tree that has invaded river systems throughout the southwestern U.S. and has caused major problems. State and local governments and private organizations spend millions of dollars each year trying to control this plant by spraying herbicides, bulldozing, burning, or by hand-cutting the trees. A small beetle from China has been released in the U.S. that feeds exclusively on saltcedar. The biology of this insect was studied in the laboratory and in the field to determine how fast it reproduces and what factors are optimal for it. A physical description of the beetle is given, along with pictures of the larvae and eggs. We anticipate that this insect will reproduce well and will cause significant damage to saltcedar trees in different areas of the U.S. where it is a problem.
Technical Abstract: Adults and larvae of Diorhabda elongata Brulle subspecies deserticola Chen feed on the foliage of saltcedars (Tamarix spp.). The larvae have three instars. All instars are black, the 2nd with an indistinct, and the 3rd with a distinct yellowish lateral stripe; full-grown larvae reach ca. 9 mm in length and pupate in cells in litter on the surface or in a shallow soil. Adults are yellowish with two dark brown stripes on each elytron. Duration of the egg averaged 5 days, 1st instar 4.9 days, 2nd instar 4.8 days, 3rd instar 7.4 days, prepupa 4.8 days, and pupa 7.1 days at 24.1 C. Pre-oviposition averaged 3.9 days and females oviposited over a 12-day period (range 1-35 days) and laid an average 194 (max. 550) eggs each. Degree-day accumulations for the development of each stage were 234.2 for the three larval instars and 91.3 for the pupa. Net reproduction rate (Ro) in the laboratory at 23.6 C, and on the best Tamarix accession, was calculated at 88, generation time at 37 days, and intrinsic rate of increase (rm) at 0.112, giving a population doubling time of 6.2 days. In field cages in 6 western states, overwintering adults emerged from 24 April to 8 May, adults of the first generation from late June to mid July, and the second generation in early September (these adults overwintered). A photoperiod of less than 14 1/2 h appeared to result in adults entering reproductive diapause. High populations developing in field cages caused dieback of some of the Tamarix trees. In some areas of the U.S., D. e. deserticola appears to be a safe and potentially a highly effective control agent for saltcedar.