Biological Control Agent: Chrysolina quadrigemina (Suffr.)

Invasive Plant Species Attacked: St. John's wort (Hypericum perforatum

Type of agent: Foliar feeding beetle

Status

Description and Biology

Adult:

The beetles are metallic bronze, green, blue, purple or black coloured and measure 6.1 - 7 mm long. The adults emerge in early June and begin feeding in clusters on young terminal leaves, flower buds or the underside of leaves. They continue to feed until leaf drop in July and early August. Reproduction is related to day length, the longer daylight, less feeding and reproduction occurs. This changes when day length is reduced. At this time they move into plant litter and await the fall rains which break their dormancy and encourage them to return to the upper plant portions to mate. Females oviposit up to 1500 eggs individually or in small clusters onto winter basal foliage.

Egg:

The eggs are reddish coloured and measure 1.2 mm x 0.5 mm. They overwinter and hatch the following spring. Chrysolina quadrigemina eggs are more resistant to desiccation than those of C. hyperici and C. varians.

Larva and pupa:

The plump, hump-backed larvae, initially orange coloured, change to dirty pink-grey as they mature. Newly hatched larvae usually appear in the spring, although some will hatch in the fall. They feed on leaf buds and immature leaves causing complete defoliation before moving onto adjacent plants. Feeding on St. John's wort causes the larvae to become light sensitive. Photosensitivity prevents them from feeding during the day, therefore, they must feed during low light periods, and do so before sunrise. After the morning feed they seek shade and protection, the smallest hide in leaf buds while the larger ones move under the plants or into the soil. They resume feeding at sunset. In mid May the larvae are mature and burrow into the soil and create a pupal cell.

Overwintering stage:

Usually they overwinter as eggs on basal leaves. In mild climates the larvae and adults will survive the winter if temperatures remain above -8°C.

Location and effectiveness of attack

Early spring larval feedings on fleshy new growth cause the most damage; this timing is the controlling key. Although adult feeding can be impressive, it has less impact than larvae feeding. Heavy fall feeding may cause some impact on the plants ability to overwinter.

Predicted and native habitat

C. quadrigemina prefer elevations below 1000 m and sites with less summer precipitation than other Chrysolina spp. It is best suited for maritime ocean climates and dry continental habitats. Abundant populations are found in Mediterranean type habitats. It requires open sunny locations as it is intolerant of shade. Dry summers are necessary to avoid breaking their mandatory dormant period. Locations with frequent summer rains will break dormancy, effecting the agent's survival.

C. quadrigemina has the most southern native European distribution of all the Chrysolina species released in BC. It has a range from northern Africa to Denmark (but is absent from mainland Sweden). It tolerates dryer climates than C. hyperici. It requires snow cover or plant litter in areas that experience severe frost.

British Columbia Experiences

Origin:

C. quadrigemina released in BC came from reared populations in Loftus, California. California sources came from Australia originating from Mediterranean France stock.

History:

C. quadrigemina was one of two Chrysolina species introduced to BC near Christina Lake in 1952. Imported populations for field release continued for several years. Over the next few years Chrysolina species were released in several locations in the southern interior. These early established releases provided collection sources for future BC populations and the first field collection occurred in 1981. Subsequent releases have established and the beetles have dispersed freely with limited assistance.

Habitat:

Pure C. quadrigemina and mixed populations have been released into the Coastal western hemlock and Interior Douglas-fir biogeoclimatic zones. Establishment and dispersal of Chrysolina speceis have been found in Coastal Douglas-fir, Coastal western hemlock, Engelmann spruce subalpine-fir, Interior cedar hemlock, Interior Douglas-fir, Montane spruce and Ponderosa pine zones. It has spread through the Fraser Valley and lower mainland, adapting to the higher precipitation levels. Larvae are readily seen in May with adults abundant in June.

Field results:

In recent years St. John's wort has been re-establishing and, therefore, renewed efforts have been underway to assist with redistributing the beetles in mixed populations. In the southern interior, larvae are readily seen in May and adults are abundant in June.

Collection for redistribution

By early June, adults can be collected by sweeping as they cluster on the plants.

Notes

C. quadrigemina are very similar to other Chrysolina species making identification difficult in the absence of the other species for comparison. C. quadrigemina adults are larger and often lay more eggs in the fall than in the spring than C. hyperici.

C. quadrigemina larvae emerge slightly earlier in the spring than C. hyperici.

References

Harris, P. 2003. Classical biological control of weeds established biocontrol agent Chrysolina quadrigemina (Suffr.). Defoliating beetle. Gov. of Can., Agriculture and Agri-Food Canada. May 20, 2003. http://res2.agr.ca/lethbridge/weedbio/agents/achryqua_e.htm

Harris, P. and D. P. Peschken. 1971. 32. Hypericum perforatum L., St. John's wort (Hypericaceae). Biological Control Programmes Against Insects and Weeds in Canada 1959-1968. Commonwealth Agricultural Bureaux. Pp. 90.

Kelleher, J. S. and M. A. Hulme, (editors). 1984. Biological control programmes against insects and weeds in Canada 1969-1980. Commonwealth Agricultural Bureaux.

Manitoba Agriculture. No date. St. John's wort (Hypericum perforatum L.). Brochure. Gov. of Man.

MFR staff observations and comments

Powell, G. W., A. Sturko, B. Wikeem and P. Harris. 1994. Field guide to the biological control of weeds in British Columbia. B.C. Min. For. Res. Prog.

Rees, N. E., Quimbly, Jr., P. C., G. L. Piper, E. M. Coombs, C. E. Turner, N. R. Spencer, L. V. Knutson (editors). 1996. Biological control of weeds in the west.