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)

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) 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.                                 HOME     Back