Bruchidius villosus 
<<back to Scotch broom
Common Name
Scotch broom bruchid
Weeds Impacted
This beetle attacks Scotch broom, Portuguese broom, Spanish broom, and French Broom. Larvae inhibit plant reproduction by feeding on developing seeds.
Insect Description
Adults are small (2 mm or approximately 1/16 inch), grayish beetles with short wing coverings. Eggs are clear, oblong and visible on the surface of young developing pods (see picture). Larvae are difficult to observe as they are inside the developing seeds. If found, they are very small and whitish with a brown head capsule.
Life Cycle
Adults emerge in the spring from overwintering, feed on pollen and remain active throughout the blooming period from May through June. Females glue their eggs onto small developing seed pods. Once the eggs hatch, generally one to two weeks, the larvae tunnel into seeds, feed, and then pupate within the seed coat. Generally one larva is completes development per seed. Pupation lasts from 10 to 20 days and new adults emerge in July and August when the Scotch broom pod cracks open (dehisces).
Field Identification
Two other beetles may be found on Scotch broom flowers—a vetch bruchid (Bruchus brachialis) and the Scotch broom seed weevil (Exapion fuscirostre). Bruchidius villosus and B. brachialis can be distinguished from the weevil by their lack of a snout. Bruchidius villosus can be distinguished from B. brachialis by its smaller size and its dark-colored legs and antennae (the front legs and antennae of B. brachialis are yellowish).
Availability
This beetle is widely available in Washington and Oregon. Adults are collected in early May for redistribution. To inquire about availability and to request this biocontrol agent, please download, complete and submit this form.
Comments
Bruchidius villosus does best in sunny, open sites. Populations generally take four or five years to build to collectable levels. Earlier research suggested that B. villosus would not survive at elevations higher than 305 m (1000 feet) but in 2009, the beetle was recorded in Washington and Oregon at elevations substantially higher.
In North Carolina, seed destruction by B. villosus is frequently more than 80%, while in Oregon, in 2004, reductions were between 10 and 25%. This rate is expected to be higher as beetle populations have established, dispersed and increased.
Parasitoids regularly attack both B. villosus and E. fuscirostre, although their impact on the biocontrol agent populations are currently unknown. Indications of parasitism are noticeable by small emergence holes on the pod exterior.
Using the Agent: Integrated Weed Management (IWM)
Beetles should only be released where infestations of Scotch broom are large and immediate eradication is not the primary objective. This beetle can be used in combination with the Scotch broom weevil (Exapion fuscirostre). Most treatments are not directly compatible with the use of these biocontrol agents. Any control methods that prevent flowering and seed production will reduce or eliminate biocontrol populations. Biocontrol agents can be used within large patches and satellite patches (which lead to increased spread) can be controlled using other management tools.
Smaller infestations and younger plants can either be dug or hand-pulled using tools such as a Weed Wrench ™. Cutting older stems (greater than 2” in diameter) at the base can effectively eliminate some Scotch broom plants.
Control of Scotch broom can be difficult and requires an integrated strategy. Herbicides can be effective, if used on regrowth from mowed or cut Scotch broom, in fall and the following spring. Consult with your county weed office, Extension office or an IWM practitioner to determine which herbicide treatments are safe and appropriate.
Any management of Scotch broom should involve revegetation with native or other desirable plants. Revegetation promotes competition between plants, which can stress weeds and allow for more effective treatment. Method of control will determine when, where, and how often sites will need to be reseeded or replanted. To learn more about revegetation and IWM, click here.
References
Coombs, E. M., J. K. Clark, G. L. Piper, and A. F. Cofrancesco, Jr. 2004. Biological Control of Invasive Plants in the United States. Western Society of Weed Science, Oregon State Univ. Press, Corvallis.
PNW Extension Publications. 1998. Scotch Broom. PNW Extension Bulletin 104.
Photo Credit
Bruchidius villosus adult - Ingrid Altmann, http://www.koleopterologie.de/gallery/FHL09B/bruchidius-villosus-foto-altmann.html
Bruchidius villosus adults and eggs - IWCP staff
Secondary content using h2 tag. Column 2
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
Heading using the h3tag
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.