Insect : beetle/weevil (Coleptera : Curculionidae)
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Scientific name: Ceutorhynchus litura
Common name: Canada thistle stem weevil (1)
Order/Family: Insect : beetle/weevil (Coleptera : Curculionidae) (1)
Origin: Ceutorhynchus litura is originally from Germany. (1) They were moved over into Canada in 1965 and then into the United States in the the earlier 1970's. (2)
Overwintering Stage: The adults are are basically in the soil next to the plant or they reside in the plant, close to the soil. (1)
Egg Stage: The eggs are placed in little holes in the leaf of the plant while it is still below 2 inches high, after this period, the plant is no longer alluring to the insects for their eggs. They tend to lay their eggs during March and April all the way up to about mid-May. They carry about 120 eggs per insect and tend to lay their eggs on the newer, younger shoots of the plant. (1)
Photo below by: Noah Poritz, www.bio-control.com
Photos by the USDA-ARS
Larval Stage: The larvae have the looks of a white, slug like worm, with one pointed end. The larvae if young eat the tissues of the leaf and then work their way into the main stem. The older ones work their way into in the main stem, and they mine the stem, root, and root crown. (1)
Pupil Stage: This stage lasts from two to three weeks. The cocoon they wrap around themselves is made of silk and soil parts and has the shape of an oval. This period occurs entirely in the soil. (1)
Adult Stage: As adults they are only about .12 to .16 inches in length. They have a long snout and a white haired T marking upon their back which is quite prominent. They have black and have white hairs upon them. They are located in the fields during the months of August to May and June. In some places you may even locate them in the month of July, as well. (1)
Damage to host
Stage: Larval and adult feeding does not have too much of an impact upon the plant. There is other damage that comes to the plant through the exit holes that the insects make as they leave the plant. Other creatures crawl in and do the damage that the Ceutorhynchus litura could not. The damage of the larvae is not apparent upon looking at the plant but the larvae as they grow eat much of the stem and this causes the underground root to rot, leaving little room for survival. (1)
Plant Species Attacked: Canada thistle (Cirsium arvense). (1)
Location: The insects feed on the stem and the crown of Canada thistle when they are larvae. As adults they feed on the leaf and stem tissue. (1)
Method: Ceutorhynchus litura eats away the inside of the stem when it is a growing larvae, and then it eats a hole near the bottom of the stem, this lets other insects in to finish the job of destroying the plant. The adults do not do much of the impact, they just eat parts of the leaf and stem. (1)
Focus: Ceutorhynchus litura focuses on the stem, the crown, and the leaves. (1)
Favorable/Unfavorable Release Habitats: For these insects the best place would be a one where there is little agricultural development, plentiful in Canada thistle but lacking irrigation or mowing. (1)
How and where to collect, transport, and release
Collect: You can collect these insects by sweep netting Canada thistle stands on a warm, non-windy day. Using your net, always sweep in a bottom to top motion up the plant. Often the insects will act as though they are dead, but you will easily be able to tell when they start to move. (4)
Transport: In order to transport them you must put them in some sort of container (white paper ice cream containers suggested) with some Canada thistle leaves for them to cling to, eat and for moisture. Put this container in a cooler, with an ice pack, but make sure the containers do not come into direct contact with the ice (wrap the containers in newspaper). If you pack them in this fashion then they should last several days. They can be stored on a refridgerator (but not in a freezer!). (5)
Release: When you release them you need to but them in a favorable release site. Simply dump them out of the container, and be careful not to step on them. (5)
How to redistribute once established: If you are redistributing them on your own land then you can just collect them in a net, turn the net so that they cannot escape, and then take them to wherever you need to redistribute them and dump them out. They can also be stored in a refrigerator for several days. (5)
Where and how to purchase: These insects are available in many ways, one certain way is to order them from the Biological Control of Weeds, Inc. on Weeds website below. The cost of for 105 insects is $250.00. (3) You can also get them at times from your local weed coordinator and your extension agent. (5)
1) Rees, Norman, et. al., Ed., Biological Control of Weeds in the West, Western Society of Weeds Science in Cooperation With USDA ARS, Mt Department of Ag. and MT State Univ., Color World Printers, Bozeman Mt, Feb., 1996.
2) Ted Evans, Extension Entomologist, Utah State University Extension, Fact Sheet No. 92, November, 1993, Extension Entomology Department of Biology, Logan, UT 84322, Online [Available] Http://extension.usu.edu/ipm/insfact/fact92.htm.
3)Biological Control of Weeds, Inc. 1418 Maple Drive Bozeman, MT 59715 Phone 406-586-5111• FAX:406-586-1679 1-800-334-9363•
Email: firstname.lastname@example.org. Online [Available] http://www.bio-control.com.
4) Powell, G.W., A. Sturko, B.M. Wikeem, and P. Harris. 1994. Field Guide to the Biological Control of Weeds in British Columbia. Ministry of Forests Research Program.
5) Breitenfeldt, Todd, Whitehall High School Science Teacher, Whitehall High School, P.O. BOX 1109, Whitehall, MT, 59759. (406) 287-3862.
By: Lillian Early, WHS student 1-14-02.
Update: Tyrell Frazer, WHS student 2-15-08.
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