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Thistle Stem Weevil (Ceutorhynchus litura)

Generations per year:  One

Growth:  4 stages of growth

Egg—up to 120 eggs may be laid in March-mid May when plants are about 2 inches tall. 

Larval—newly hatched larvae mine the tissues of the leaf toward the main vein.  Older larvae mine stem, root crown and roots. 

Pupal—pupation occurs in the soil and can last up to three weeks.

Adult—can be found in fields from August until the following May, June and in some areas, July.  Adults are 0.12 to 0.16 inches long (tiny), with a long-snout.  It is black with whitish hairs with a T-shaped marking on the back.

 Overwintering stage—Adult—can be found in the soil near the plant or on the plant next to the soil.

Destructive stage—larval feeding within the stem and crown of plant then chewing an exit hole below the surface.

Impact on the Canada thistle—the insect does not kill the plant, however, by rotting the underground shoot during the winter months reduces shoot production the following spring.  When the larvae chews an exit hole, this introduces an access site for small insects, other arthropods, nematodes and pathogens to the plant.


  •  Disturbed areas where Canada thistle is thick.
  • Surface water nearby or high relative humidity

Field subject to flooding, grazing, mowing and chemical treatments are not conducive to weevil survival.

Release Date:  Thistle Stem Weevils are typically released in mid July to August. 

Cost:  A carton of adult stem weevils = approximately 105 insects

$200.00 plus overnight shipping costs to apply

If you are interesting in ordering Thistle Stem Weevils, please submit the following form or call (406) 485-2744 x100.

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