flowering near Peck, Idaho

Seedling stage

Rosette stage

Bolting stage

Small buds with yellow-green spines begin to be visible at the top.

Spines protrude more than half of the bud length.

Spines are equal to or greater than 45° angle from stem

Spines are straw-colored and equal to or greater than 90° angle from stem.

Flowering stage

Seed formation stage

Mature stage

Seed dissemination stage

Senescence stage

Urophora sirunaseva gall

feeding on BU-1 bud

oviposition hole

exit hole

dead and bent yellow starthistle head from weevil feeding

face down in starthistle flower head

woody gall

emergence hole

example of yellow starthistle infestation suitable for a biological control program

for insects

collecting yellow starthistle biocontrol agents

styrofoam-lined shipping box containing blue ice pack and biocontrol agent cartons

screen tent cage in which to release and contain knapweed bioagents

monitoring for biocontrol agents

measuring knapweed height at a quantitative monitoring site

monitoring a infestation