Overwintering State(s): Adult. Then are active in the spring to feed, mate, and oviposit. (6)
Egg Stage: Females lay the eggs inside of the closed head buds. They do this by chewing a hole through the involucre. The hole is then covered by frass. This occurs in early to mid-summer. The eggs will hatch in three days. (5-6)
Larval Stage: The larva develops inside by eating the receptacle tissue. They develop completely in sixteen days. (5-6)
Pupal Stage: They pupate in the seed head. The cacoon is made from chewed seeds and pappus hairs. (5)
Adult Stage: Adults start to come out in late June and July. They become beetles with long hairs on their backs. They are brown with whitish stripes. They have long skinny noses. Their total length is 4 to 6 mm or .16 to .24 inches, not including their nose. (5)
Type of Damage to Host:
Stage: Adult and larval.
Plant: Yellow starthistle (Centaurea solstitialis).
Location: Seed heads.
Host Impact: Adults feed by chewing through the sides of the involucre into closed capitula. They feed on the small heads buds which usually destroys a large number of them. (5) They will not attack commercially important or native nontarget plants. (2)
Favorable/Unfavorable Release Habitats: This hairy weevil was first introduced into the U.S. in 1990. It's habitat is cool climates. Coastal, higher elevations, and higher latitudes are unfavorable. High moisture and humidity may also be unfavorable. (5) "It probably won't work in Montana; it needs a warmer environment." (1)
How and Where to Collect, Transport, and Release: They are readily available in Arizona, California, Idaho, Oregon, and Washington. (6) To transport; you can put in a container, in a cooler with an ice pack which doesn't touch the container. To release; dump them on the plant at the site (1) These insects do best in area's with warm, dry summer climates. (3)
How to Redistribute Once Established: Adults can be swept or hand picked from the host plants.
Where and How to Purchase: Available June-July. Cost $50/100 adults per acre (6)
Remarks: This insect is a double threat to yellow starthistle.
It is attacked twice, once by the adults, and again by the larva.
With the approval from USDA's Animal and Plant Health Inspection
Service, six of the yellow starthistle insects were imported, and five
were established. Eustenopus weevil was the most effective.
Because of the dual impacts of adult and larval feeding, this weevil
is excellent biological control agent; damage is readily visible
to the naked eye at sites containing high weevil numbers. (4-6)
2) UC Cooperative Extension, 891 Mountain Ranch Rd., San Andreas, CA., 95249, (209)- 745-6477, FAX (209)-754-6472, Email email@example.com, Calaveras Cooperative Extension; Yellow Starthistle Biology and Control. http://cecalaveras.ucdavis.edu/
3) Harper, John or George, Mel, E-mail John Harper firstname.lastname@example.org,
or Mel George.