Overwintering survival, phenology, voltinism, and reproduction among different populations of the leaf beetle Diorhabda elongata (Coleoptera: Chrysomelidae)

Authors: Milbrath, Lindsey; Deloach Jr, Culver; Tracy, James

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2007
Publication Date: 12/17/2007
Citation: Milbrath, L.R., Deloach Jr, C.J., Tracy, J.L. 2007. Overwintering survival, phenology, voltinism, and reproduction among different populations of the leaf beetle Diorhabda elongata (Coleoptera: Chrysomelidae). Environmental Entomology. 36:1356-1364.

Interpretive Summary: A leaf-feeding beetle is being used to control saltcedars, exotic shrubs or trees that have invaded and are damaging river systems throughout the Western U.S. We tested populations of the beetle from four different source locations for their ability to overwinter and reproduce to help determine which population(s) to release in the Southwestern states. Two of the beetle populations had high survival over the winter whereas the other two populations had very poor survival. The beetles were capable of producing from three to five generations in a summer, and laid a similar number of eggs per female beetle. Overall, the beetle population originating from Crete, Greece seems to be the most promising for release in the southern U.S. for saltcedar control. Control of saltcedar will help improve native plant communities and wildlife habitat and insure water supplies for agriculture and municipalities.

Technical Abstract: The classical biological control program for exotic saltcedars (various Tamarix species and hybrids) has involved the assessment of different populations of the leaf beetle Diorhabda elongata (Brullé) sensu lato that are promising for release in areas of North America that are located south of 37°N latitude. We report here the overwintering survival and phenology of four D. elongata populations (Tunisia, Crete, Uzbekistan and Turpan) in east-central Texas. In addition, we investigated their developmental and reproductive biology, which also included the previously released population from Fukang, China. Overwintering survival of the adult beetles of the Crete and Tunisia populations was 80-95% and 62-67%, respectively. The Uzbekistan and Turpan beetles had less than 15% overwintering survival. All D. elongata populations began ovipositing in late March. The Turpan beetle may produce three summer generations and ceased oviposition by September. The Crete beetle produced four summer generations plus a partial fifth generation, and ceased ovipositing by mid-October. Both the Turpan and Uzbekistan beetles produced five summer generations plus an unsuccessful partial sixth generation; oviposition extended into late November. Larval development and survival were generally similar among D. elongata populations. The Turpan and Fukang beetles had a shorter preoviposition period and produced more but smaller egg masses than the other beetle populations. However, this did not alter a female’s lifetime fecundity and generally did not affect the innate capacity for increase compared to other populations. The Crete beetle appears to be the most promising for release in central Texas and points further south.