Biological Control Agent: Bruchidius villosus (F.)
Invasive Plant Species Attacked: Scotch broom
(Cytisus scoparius) and French broom (Genista monspessulana)
Type of agent: Seed feeding beetle (weevil)
Status 
Primary
Description and Biology
Adult:
The black adult weevils are 2 - 4 mm long, with parallel lines running the length of the
wing covers. Overwintered, sexually immature adults emerge in March and April and a new
generation occurs in July and August. To reach sexual maturity, adults are required to
feed on broom pollen. If adults emerge before broom is in flower, they first feed on
gorse before moving back onto broom. Oviposition begins when young green pods begin to
form. The females will lay eggs individually or in horizontal rows onto young green pods
and cement them in place. Adults are active walkers and quickly take flight once pods
open.
Egg:
Eggs are 0.3 mm long, oval and pale green coloured. During incubation, the eggs change
from the pale green to purple.
Larva and pupa:
There are four larvae instars. The newly hatched larvae move across the pod, often
leaving a very fine blue trail before chewing into the pod cavity where they attack soft green
seeds. After they have entered into the pod, their complete development occurs within
a single seed inside a closed pod. Several larvae can develop in each pod, but, each
will occupy their own seed. After a short pupation phase the new adults chew through
the seed coat, but, remain inside the pod until it splits open.
Overwintering stage:
Adults overwinter near the host plants seeking protection in plant litter or crevices.
Location and effectiveness of attack
Bruchicius villosus larvae feed on seeds. High populations can reduce seed
production which decreases plant density and spread. Adults feed on pollen, foliage and
stems.
Predicted and native habitat
B. villosus is expected to survive in any area that the host plant establishes.
Specific habitat requirements are currently being studied.
The weevil has an extensive native European range and can be found in Austria, Denmark,
Germany, Hungary, Italy, Switzerland, United Kingdom, France, Portugal and Spain.
British Columbia Experiences
Origin:
B. villosus is an adventive agent that is believed to have entered BC from the
Pacific North Western United States where releases began in 1998 from
populations collected in North Carolina. The weevils released in North
Carolina originate from stock collected in the United Kingdom.
History:
B. villosus was first discovered on Vancouver Island in 2001. Recent
investigation has found its dispersal within the Lower Mainland, in the Fraser Valley,
on Vancouver Island and on some coastal islands. In 2006, adults were collected from Vancouver Island and the
first field treatment was made in the central Kootenays. A second collection was made from a Fraser Valley site
with both B. villosus and E.
fuscirostre present for release into the Kootenays. Establishment
at both the 2006 and the 2007 sites was confirmed in 2008. In 2008,
another population was collected and was
released into a slightly more northern habitat near Upper Arrow Lake.
Habitat:
Adventive populations of B. villosus has been found dispersed within the Coastal
Douglas-fir and Coastal cedar hemlock biogeoclimatic zones. Successful establishment
has occurred from collections taken from these zones and released into the Interior cedar hemlock
zone.
Field results:
B. villosus have been found on plants adjacent to tidal
flats and in salt spray locations, which indicates it may have a high tolerance
for saline conditions. It is commonly found sharing inland host plants
with Exapion fuscriostre ,
another adventive agent. Based on the 2007 collection calculations, in
the field, B. villosus out numbers E.
fuscirostre. An estimated 2800 pods were collected and the ratio was 5680 B.
villosus to 1400 E. fuscirostre, or 80/20% B. villosus to E. fuscirostre per
pod.
Not available for general distribution at this time.
Notes
B. villosus is more active than E. fuscirostre.
E. fuscirostre can be confused with B. villosus in the larvae
and pupae stages.
The size of the seed may influence the size of new adults. In test plots, larger
seeds produced larger adults.
References
Isaacson, Denis L. 1998. A petition to import Bruchidius villosus from
North Carolina to the western U.S. for biological control of Scotch broom (Cystus scoparius).
MFR staff observations and comments
Oregon Department of Agriculture. 2006. Bruchidius villosus. ODA
Plant Division, Noxious Weed Control. November 21, 2006. http://oregon.gov/ODS/PLANT/WEEDS/bio_profile-brvi.shtml
Paynter, Quentin, Simon Fowler, Hariet L. Heinz, Jane Memmott, Richard Shaw, Andrew Sheppard
and Pauline Syrett. 1996. Are seed-feeding insects of use for the biological control
of broom- In Proceedings of the IX International Symposium on Biological Control of Weeds.
State of Victoria Department of Natural Resources and Environment. 1999. English
broom suppression with the broom seed-feeding beetle. Landcare Notes. June 1999.
Keith Turnbull Research Institute, Franskston.
Wittenberg, R. and T. Thomann. 2000. Investigations on potential biological
control agents of Scotch broom, Cytisus scoparius. Annual Report. CABI International.
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