Yellow Starthistle flower weevel
Type of agent: Insect: Beetle, weevil (Co-leoptera: Curculionidea)
Insect Links Adults Larva Eggs Damage to plant
Origin: Northern Greece
Native: Southern Eurasia, Mediterranean basin
Egg Stage: The eggs are laid in the heads of open flowers in the incuation of four days
Larval Stage: They feed on the devoloping seeds. The total larval development period stage is 17 to 20 days.
Pupal Stage: The development starts in the damaged seeds. The process of the pupal stage is 4-5 days.
Adult Stage: The adults eat the flowers and pollen of teh yellow starthistle. They are found on the plant from late June to early August and are brown with somewhat mottled look. They have a light-colored patch on thier back. They usaually are covered in pollen. They have a body lenth of 5 to 6 mm. This doesn't enclude the snout.
When They Take Effect:
They are at their destructive stage when they become a Larval. They were made to destruct Yellow Starthistle (Centaurea solstitialis). They attack mostly the seed heads of this extravagant plant or the interior. When they feed on this thistle they eat the developing seeds and this reduces down the plant by at least 100%. As for the adults they feed on the pollon and the flowers. This my only have little impact on the plant.
When were they released?
They were first introduced to the United States in '92 in California, Idaho, Washington, and Oregon, and now are mostly established in Idaho, California, Washington and Oregon.
They like to live in mostly cool climates in the higher elevations and latitudes, and near coastal areas. There availiably is limited.
How are they collected?
The weevil can be collected in several ways. Adults can be hand swept or hand picked from the plants.
1) Rees, Norman, et. al., Ed., Biological Control of Weeds in the West, Western Society of Weed Science, in cooperation with USDA, ARS, MT Dept. of Agriculture, and MT State University, Color World Printers, Bozeman, MT, Feb. 1996.
2) Rees, Norman, et., al., Ed., Biological Control of Rangeland Weeds in the Northwest United States, Manuscript/ Rough Draft. 1996
By: Chad Housman 01\08\01
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