Diorhabda elongata - saltcedar leaf beetle.
Coleoptera: Chrysomelidae
Photo by: USDA-APHIS-PPQ.
Common Name: saltcedar leaf beetle. (1)
Origin: This species originated in central Asia. (2)
Life Cycle: Development from egg to adult requires about 3-4 weeks. (3)
Eggs: Eggs are laid in masses of 2-20 on foliage and hatch in about 7-10 days. The eggs are .99 mm by .8 mm in diameter. They are bright yellow when laid and turn to a whiteish tan as they get older. (3)
Larval: The larvae feed exclusively on the plant. Larvae are black with two longitudinal yellow stripes and complete three instars. Mature larvae are about 8 mm long and enter a prepupa stage. (3)
Pupil: The prepupa does not feed but drops to the ground and searches for a pupation site. Pupation occurs on the soil surface beneath leaf litter or in soil cracks. (3)
Adults: Adults are 5-6 mm in length and are 2-3 mm wide. They are a bright yellow color and each wing case has two black stripes down the back of it. Their thorax have a black box on both side. Its head is yellow with a black dot in the center. Females are a bit larger than males. They are sexed by a notch on the under belly of the males, and a slight bulge for females. They live for about 18 days. The adults feed exclusively on the plant and produce two or more generations of offspring per year. (1)
Host: Salt cedar or tamarisk (Tamarix ramosissima) (1)
Over wintering Stage: A three-year test in the field with beetles confined to cages showed that the beetle can survive the winter and reproduce, and that it effectively defoliates saltcedar. (1)
Type of damage to host: They not only eat the green vegetation, but in doing so create holes in the leaves through which water escapes, causing branches to wither and die. (1)
Stage/plant species: An alien tree called saltcedar that invades riverbanks, pushes out native willows, chokes streams and impoverishes riparian habitat. (1)
Location: Diorhabda elongata can be released by riverbanks, native willows, or streams where saltcedar is abundant. (1)
Host Impact: Saltcedar is a serious weed of riparian areas in the western United States. It infests over one million acres in the USA and is difficult and expensive to control, given its high regenerative capacity and high seed production. (2)
Favorable/unfavorable release areas: It's favorable release location would be around riverbanks, native willows, or streams where saltcedar is abundant. (1)
How and Where to Collect, Transport and Release: After overwintering has been demonstrated, some twigs containing beetle eggs may be removed from the big cages and established in sleeve bags on saltcedar branches outside the big cages. This should be done in two stages: 1) a small number of beetles can be removed after peak emergence from overwintering has been observed, and 2) after overwintering adults have completed oviposition and a large number of first generation larvae are present. In both stages, this release should first be made into sleeve bags outside the big cages. Also, adults can be netted from well established release sites and transported in coolers. (4)
How to Redistribute once established: When it is obvious that the adults in the cage have begun to oviposit or the first generation larvae have begun feeding, part of the sleeve bags may be removed and the rest left in place for monitoring of reproduction, development, survival, and mortality. (4)
Where and how to Purchase: Contact your local weed fighters or the National Biological Control Institute. [Several sites in Montana have shown establishment and damage to saltcedar. It is hoped that these sites may soon provide insects for collections. However, at this time these are research sites and should be left alone. See: http://www.ars.usda.gov/Research/docs.htm?docid=10524 Mr. Breitenfeldt, 2007]
Bibliography:
(1) http://www.berkeley.edu/news/media/releases/2001/05/21_alien.html, UC Berkeley, USDA biologists to release imported beetle to control saltcedar, an alien tree invading river bottoms throughout Western U.S., by Robert Sanders, Media Relations.(2) http://wric.ucdavis.edu/exotic/techtran/juli.htm, Life-History of Diorhabda elongata in Secure Field Cages, by Ray Carruthers and Tom Dudley.
(3) http://bc4weeds.tamu.edu/scleafbtl.html, Saltcedar Leaf Beetle, by Texas A&M University Department of Entomology.
(4) http://wric.ucdavis.edu/exotic/techtran/years2-3.htm, Plan for Monitoring the Effects of Releasing the Saltcedar Leafbeetle, by the Insect, Vegetation and Wildlife Subcommittees of the Saltcedar.
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By: Kyle Simons and Carl Lanz 2/25/02. Updated: Samantha Terrel 3-1-07.