Canada thistle bud weevil
then brought to Pennsylvania. (4)
Overwintering State: adult in the
Egg Stage: The female weevil will lay
her eggs on an unopened bud. She will do this by drilling a hole
into the side of the bud. If by some reason, more than one
egg is laid in a hole, only one of the larva will survive. (3, 4)
Larva Stage: While growing they
feed on the tissue part of the seeds and other flower parts. (2, 3, 4)
Pupil Stage: This takes place in
the cocoon made in the bud. (3, 4)
Adult Stage: The average body
length for these insects are from 5-8 mm. They develop in the bud and
then emerge late May and June. The adult weevils can begin mating
after about one week. They then must lay their eggs within 14-26 days
after the mating. (3, 4) Type of
Damage to Host:
Larva: This is the most destructive stage. It destroys the seeds,
pappus, and receptacle within the flower bud.
Adult: This stage stops the
of buds and the upper leaves of
Species: Canada thistle (Cirsium
Location: New buds, leaves,
and seeds (3, 4)
Host Impact: The adult
weevil, will lay its eggs by drilling a hole into an unopened
bud. Once they
hatch, the larvae will start eating the tissue part of the seed. They
will then develop into the pupa stage. The most damaging stage is
larval stage. This is where the bud is ruined, and therefore the
bud will fail to open all the way. In the end, the thistle has
reproducing. (2, 4)
Release Habitats: The weevils do well in a wide
climates. This means that they are very good at surviving many
Transporting, and Releasing: After you
to collect your weevils, use a sweep net to gather them.
you have enough, store them in a cool place. They should be in a
cardboard box or container. Try your best to release the insects
within several days of your gathering. You should collect and
these insects in late May to early June. (1, 2, 3)
Purchasing: If you would like to purchase this
insect, contact your county extension office or Weed District.
also visit these web sites: Bio-control, Integrated
Weed Control, and other places.
Remarks: Larinus planus is a bud weevil
mainly on Canada thistle. It seems that once these insects are
set into a big patch of Canada thistle, they do extremely well. The
most destructive stage is the larva stage.
1. Burnett, Tom, Sprig 2000, Biological
Information [web site], Available: http://www.marathonbiological.com/lplanus.htm,
Last updated: 2000
2. Harris, P., Lethbrigge Research
site], Available: http://res2.agr.ca/lethbridge/weedbio/agents/alaripla.htm
, Last updated: 12/28/2000
3. Unknown author, PRIDE, [web site]: http://users.aol.com/prideedu/planus.htm
updated last: unknown.
4. Rees, Norman, et. al., Ed.,
of Weeds in the West, Western Society of Weed Science, in
with USDA ARS, MT Dept. of Ag, and MT State Univ., Color Printers,
MT, Feb., 1996.
By: Kara Voeks 1/9/02.
Updated By: Tyrell Frazer 2/15/08.
to Biological Control mtwow.org