Hemp Dogbane
Hemp dogbane is a tallgrowing, perennial broadleaf weed often mistaken
for common milkweed. It spreads by seed and overwintering rootstock. In
Ohio and Indiana, hemp dogbane tends to appear in areas that have not
been tilled for a number of years.
Noncrop/Fallow Areas. Glyphosate (3 lbs ae/A or 2% solution for
spot treatment) or glyphosate + 2,4D (1.13 lb ae/A + 0.5 lb ai/A) can be
applied when dogbane are in the latebud to flower stage of growth.
Treatments following crop harvest or mowing should be delayed until
weeds regrow to a mature stage.
Corn. Glyphosate (Roundup Ready corn) applied at 0.75 lb ae/A
will suppress or control dogbane, but a second application may be
necessary. Postemergence application of Spirit (1 ounce/A) or Beacon
(3/4 ounce/A) plus 1/2 pint/A of 2,4-D will provide the most effective
suppression/control of dogbane in corn. Other postemergence treatments
with activity include NorthStar, Yukon, and combinations of dicamba (1/4
to 1/2 pint/A) with Spirit or Accent (2/3 ounce/A). Dicamba (1/2 to 1
pint/A) applied alone will suppress dogbane, with best results if
dogbane plants are at least 8 inches tall. If corn is less than 8 inches
tall, the higher rate can be applied. Use drop nozzles where directed by
the label to avoid crop injury in late postemergence applications.
Soybeans. Glyphosate (Roundup Ready soybeans) applied at higher
labeled rates is the only effective postemergence treatment. A second
application may be necessary. Late postemergence applications, when
plants are in the bud to flower stage, will provide the most complete
control of underground plant parts.
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Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
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