Chrysolina quadrigemina
Common name: Klamath
weed beetle.
Type of agent: Insect: Beetle (Coleoptera: Chrysomelidae).
Insect Links Pictures
Native distribution: From North Africa to Denmark, but does not reach
the Swedish border.(2)
Original source: Australia (from material previously collected from
southeastern France).(1)
The Life Cycle:
Overwintering stages: Egg, larval, and (sometimes) adult.(2)
Egg Stage: Eggs are usually deposited on leaves of St. Johnwort in
the fall, but sometimes in the spring. They are laid singly or in clusters
of two to four on the underside of the leaves. Eggs that are deposited
on foliage during the late fall or early winter can survive and hatch the
following spring. Each female may lay several hundred eggs during her
lifetime. Eggs are oval and orange to reddish in color. (2)
Larval Stage: Eggs hatch about three weeks after they are laid.
The larva migrate to the leaf buds and immature leaves. Larvae can completely
defoliate a plant before they reach maturity, which forces them to move to
other plants. When the larva mature, they burrow into the soil, create
a cell (chamber) and pupate within it. Larvae are somewhat humpbacked
or C-shaped and plump. They are orange first and become a dirty, grayish-
pink with age. Larvae of this species resemble those of C. hyperacid.
(1,2)
Pupil Stage: Mature larvae burrow into the soil in February
and March and pupate in oval cells. They emerge from late April until
June. The orange pupae are oval; the wing pads, legs head, and antennae are
antennae. (1)
Adult Stage: Adults behave much like that of C hyperacid.
They emerge in the spring, and feed for several weeks then enter the soil
to restful rains activates the adults to mate and lay eggs. The oval
beetles are shiny, metallic black, blue, green or bronze, and 5 to 7 mm
(about 0.2 to 0.28 in) long. (1)
Type of Damage to Host: Larvae: They eat the roots of the weed.
This destroys the growth of the weed almost completely in the spring.
Adult: They eat the bud, which also destroys the weed. Plant Species: St.
Johnwort Location: Buds and roots. (2)
Impact on the Host: Larval feeding in the fall and spring reduces the
foliage and lowers root reserves making it very difficult for the plants
to survive the winter or summer environmental conditions. (1)
Releasing Habitats: The beetles like moist or dry regions. They
don't like shaded, rocky areas, or bare lands. (1,2)
Comments: The introduction of Crinoline Quadrigemina into Californian
1946 caused such an impact upon the St. Johnwort population that the weed
was removed from the noxious weed list there. The subsequent redistribution
of this agent throughout much of northwestern Canada and United States raise
false hope that this agent could control all popopulationsf St. Johnwort.
However, in many locations where the insect is established, many of the St.
Johnwort populations are still increasing in size and density, while in others
there is little change. The same climatic factor inhibiting the effectiveness
of C. hyperacid also appear to affect C. quadrigemina populations.(1,2)
Useful
Links:
1. http://res2.agr.ca/lethbridge/weedbio/agents/achryhyp.htm
2. http://www.for.gov.bc.ca/HFP/PUBS/INTEREST/Bioagent/stjohns.htm
3. http://www.co.stevens.wa.us/weedboard/htm_bio/chrysolina_spp_.htm
4. http://www.ento.csiro.au/research/weedmgmt/weedsdespatch/despatchthirteen.html
5. http://www.montana.edu/wwwpb/ag/st_johns.html
6. http://faculty.ucr.edu/~legneref/biotact/ch-66.htm
7. http://www.3rivers.net/~tomelpel/weedsinfo/Hypericum_perforatum.htm
8. http://www.symposium.ars.usda.gov/tours/biocontrol.html
9. http://www.bio-control.com/7d.asp
10. http://www.integratedweedcontrol.com/stjohn.htm
(1)
Reuse, Norman, ET. Al., Ed., Biological Control of Weeds in the West, Western
Society of Weed Science, in Cooperation with USDA AS, MT Dept. of Erg,
and MT State Univ., Color Printers, Bozeman, MT, Feb., 1996.
(2) The defoliating Klamath Weed Beetle, Crinoline quadrigemina,
feeds on the foliage of this weed in both the adult and larval stages.
Written by: Andy. Mc. & Ben. Bo. 02-2003.