Hosts or Prey
Weedy saltcedars, or tamarisks
Identification
The most prevalent Diorhabda species in California is the introduced Mediterranean tamarisk beetle, D. elongata. Adults are about 3/8 inch (9 mm) long. They are mostly yellowish brown or green with brown to dark green longitudinal stripes on the wing covers.
Eggs are yellowish orange, about 1/16 inch (1.5 mm) long, and globular. Eggs can be found on saltcedar foliage in groups of several to about 20.
The larvae are elongate with distinct segments. The first instar is black and about 1/16 inch (1.5 mm) long. Second and third instars are mostly grayish black with a distinct longitudinal yellowish green stripe on each side of the abdomen. Mature larvae (third instars) are about 3/8 inch (9 mm) long.
Pupae occur hidden in liter and topsoil. They are oval shaped, yellow, and about 5/16 inch (7 mm) long. As pupae age, they develop distinct appendages folded against the body.
Life Cycle
Mediterranean tamarisk beetle develops through four life stages: egg, larva, pupa, and adult. Overwintering is as adult beetles in protected locations. Overwintering adults become active during April or May when they feed and mate and the females begin laying eggs. Eggs laid in spring mature into adults in July. A second generation of adults appears in August to September and these overwinter.
Adults live for about 3 weeks during which females each lay about 200 eggs. The hatching larvae develop through 3 increasingly larger instars. Mature larvae (prepupae) drop or walk to the ground and pupate individually in cells in litter on the ground or in topsoil. The emerging adults fly or walk to saltcedar, feed, and during spring and summer reproduce on saltcedar. The second generation of adults that emerges in late summer or fall does not reproduce until the next spring.
Egg to reproductive adult development time is about 7 weeks when temperatures average 80ºF. Mediterranean tamarisk beetle has 2 generations per year.
Habitat
Saltcedars are exotic, perennial, deep-rooted shrubs or small trees that invade riparian areas and consume much space and water. These weeds outcompete and exclude native vegetation that provides habitat for various desirable species including bighorn sheep, birds, and fishes. Wildlife populations decline after saltcedars invade their habitat.
As part of a classical biological control program, 4 Diorhabda species of leaf beetles were collected by entomologists with the U.S. Department of Agriculture for study under quarantine. After studies confirmed the beetles do not feed and reproduce well on native plants the beetles were mass reared and released into the Western United States beginning in 1999. Introduced were the northern tamarisk beetle (D. carinulata) from Kazakhstan and China, Mediterranean tamarisk beetle from Greece, larger tamarisk beetle (D. carinata) from Uzbekistan, and subtropical tamarisk beetle (D. sublineata) from Tunisia.
Adults and larvae chew and feed on foliage of saltcedars (Tamarix species). The introduced beetles severely defoliate saltcedars, greatly reducing the weeds' reproductive ability and causing some plants to decline and die prematurely.
Species
Diorhabda species are not native to the United States. Five similar Diorhabda species leaf beetles are native to the Mediterranean region eastward to Western China. These include southern tamarisk beetle (D. meridionalis) and the four species named above.
More Information
- Biology of Diorhabda elongata deserticola (Coleoptera: Chrysomelidae), an Asian Leaf Beetle for Biological Control of Saltcedars (Tamarix spp.) in the United States, Biological Control
- Ecological Interactions in the Biological Control of Saltcedar (Tamarix spp.) in the United States: Toward a New Understanding (PDF), Proceedings of the X International Symposium on Biological Control of Weeds
- Release, Establishment and Realized Geographic Distribution of Diorhabda carinulata and D. elongata (Coleoptera: Chrysomelidae) in California, U.S.A., Biocontrol Science and Technology
- Saltcedar , Center for Invasive Species Research, UC Riverside
- Taxonomic Revision and Biogeography of the Tamarix-feeding Diorhabda elongata (Brullé, 1832) Species Group (Coleoptera: Chrysomelidae: Galerucinae: Galerucini) and Analysis of Their Potential in Biological Control of Tamarisk (PDF), Zootaxa
Scientific classification:
- Phylum: Arthropoda
- Class: Insecta
- Order: Coleoptera
- Family: Chrysomelidae
