Biological Control Agent: Agrilus hyperici (Cr.)

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

Type of Agent: Root feeding beetle

Status

Description and Biology

Adult:

Adults are elongated, 4 - 5 mm, brown (reddish-bronze) beetles. Their bodies appear somewhat flattened, tapering towards their posterior. They emerge from late June to early August. Mating begins immediately. Females lay up to 200 eggs individually onto plant stems near the soil surface. Most egg laying is completed in July. Adults are active during the heat of the day, dispersing freely and residing on upper plant parts.

Egg:

Eggs are greyish coloured. Incubation time and requirements are not known at this time.

Larva and pupa:

Larvae are white with flat brown heads. Upon hatching, the first instar mine down the stem towards the root, feeding just below the epidermis. This feeding leaves a visible raised feeding trail. All other instars feed within the root, packing their feeding tunnels with debris and frass. Multiple larvae can exist in large roots.

Overwintering stage:

Mature larvae overwinter in host plant roots, pupating the following summer.

Location and effectiveness of attack

Larvae root feeding weakens and often kills the plant. They can consume all root tissue, creating stunted stem growth and reducing floral and seed production. Adults feed on the foliage but have little impact on the plant. Agrilus hyperici attacks plants in shaded areas which are commonly avoided by other St. John's wort agents. Larvae can be infected with fungal infections when developing in moist conditions.

Predicted and native habitat

A. hyperici requires warm, dry locations and tolerates sun and shade. Moist sites are avoided. They have a preference for large stemmed plants on which to feed, develop and reproduce. In the United States it is common in mountain areas, but sites over 1000 m in Canada may not be productive.

In its native distribution in south, central and east Europe it is restricted to dry mountain sites and becomes most abundant in its most southern limits.

British Columbia Experiences

Origin:

The earliest (1950's - 1970's) A. hyperici released in BC came from California and the later (1980's) came from Idaho. Both USA sources originate from France stock.

History:

The first A. hyperici release was made in 1955 near Christina Lake. Another release did not occur until 1964. A third attempt to establish a population was tried in 1977. Releases made between 1987 and 1989 were made from the Idaho populations. In 2008 the first field collection was made. Slow establishment has limited the redistribution efforts.

Habitat:

A. hyperici has been released into the Coastal Douglas-fir, Interior cedar hemlock and Interior Douglas-fir biogeoclimatic zones. There is a release record indicating that it may have also been released into the Engelmann spruce-subalpine fir zone, but this still needs to be confirmed. Establishment and dispersal has occurred in the Interior cedar hemlock, Interior Douglas-fir and Ponderosa pine zones. The status of the recent (2008) release made in the Coastal Douglas-fir zone has not been determined at this time.

Field results:

In 2008 adults have been found dispersed several km away from the earliest release. At a release site near Grand Forks A. hyperici is known to have established and dispersed in ideal habitat. At this site larvae were found in late May. By mid June they were pupating, and in early July through early August adults were present. The first field collection was made in 2008 from the Grand Forks population and released on Vancouver Island. This also was the first attempt to move A. hyperici into the west coast habitat. Recent investigations indicate that it is dispersing in the Southern Interior Forest Region. A. hyperici have been found sharing sites with Chrysolina spp., Aplocera plagiata , and Aphis chloris.

Collection for redistribution

Not available for general distribution at this time.

Notes

A. hyperici disperses widely from release locations and often cannot be recovered for several years at new sites.

References

Harris, P. 2003. Classical biological control of weeds established biocontrol agent Agrilus hyperici (Cr.). Root-boring beetle. May 20, 2003. http://res2.agr.ca/lethbridge/weedbio/agents/aagrilus_ehtm

McLeod,J. H. 1962. A review of the biological control attempts against insects and weeds in Canada. Part I - Biological control of pests of crops, fruit trees, ornamentals, and weeds in Canada up to 1959.

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.