glyphosate
Rate 2.25 lb ae/A
Time Apply to actively growing milkweed that has reached the late bud to flower stage of growth.
Remarks After small grain harvest or mowing, let milkweed regrow to mature stage before treating. Allow 7 days or more after application before tillage.
Caution Glyphosate controls grasses as well as other vegetation in treated areas.
Site of action Group 9: inhibits EPSP synthase
Chemical family None generally accepted
picloram (Tordon)
Rate 1 lb ae/A
Time Apply at bud to early bloom to actively growing milkweed.
Caution Most formulations are restricted-use herbicides. See label for grazing restrictions. Do not contaminate water. Potatoes, beans, and many other crops are very sensitive to picloram. Do not use in diversified cropping areas. Apply rates over 0.5 lb ae/A (1 quart/A) only as a spot treatment not to exceed 25% of a landowner's acreage in any given watershed in a single season.
Site of action Group 4: synthetic auxin
Chemical family Pyridine