Bear Lodge Project – Bull Hill Mine
January 2013
Weed Management Plan
12
having short straight awns.
Management Objective
: Containment
Integrated Management
Chemical: Nicosulfuron, glyphosate, and fluazifop are all effective control agents.
Biological: There are no known biocontrol agents approved for use.
Cultural: Increasing competition of desirable vegetation by seeding may reduce
competitiveness.
Manual/Mechanical: Plowing or disking is successful if done multiple times per year to break
up rhizomes.
Bull thistle
Bull thistle is a biennial that grows erect with many spreading branches, growing 2 to 5 feet tall, and
reproducing only by seed. Rosette forms the first year with a flowering stem forming the second
year. Leaves are green with sparse hair, short spines on the leaf surface, and sharp spines on the
margins. Flowers are terminal 1 ½ to 2 inches in diameter with spines on the bracts, dark purple in
color. Roots consist of a short fleshy taproot. Seeds are straw colored with a brown or black stripe
running lengthwise and a protrusion at one end.
Management Objective
: Containment
Integrated Management
Chemical: Clopyralid, dicamba + difluferzopyr, clopyralid + 2,4-D, aminopyralid,
metsulfuron, picloram, and chlorsulfuron are all effective control agents on rosette
stage.
Biological: Thistle stem hover fly (
Cheilosia corydon
), Musk thistle crown weevil
(
Trichosirocalus horridus
), and Bull thistle seed head gall fly (
Urophora stylata
)
are all effective control agents.
Cultural: Grazing and land use management to improve grass cover may reduce
competitiveness.
Manual/Mechanical: Mowing, hand cutting, and digging are all effective techniques for
control.
Common mullein
Common mullein is a biennial that produces a large rosette of fuzzy leaves the first year and a single
stout erect stem the second year reaching 2 to 6 feet tall. Leaves are alternate and overlapping,
densely wooly, and light green in color. Flowers are sessile, yellow in color, with five petals
growing more than an inch in diameter. Roots consist of a relatively shallow taproot. Seeds are
small angular and brown in color, approximately 1/32 inch long.
Management Objective
: Containment
