The dogbane beetle is not a pest and does not require control. These beetles feed only on the poisonous sap of milkweed and dogbane, not on other crops. Milkweed and dogbane, however, commonly grow interspersed with other crops, creating the illusion that the beetle may be feeding on your crops. The larvae feed exclusively on dogbane and milkweed crops. If you desire to get rid of these nondamaging insects, you must control your milkweed and dogbane populations.
Identify local patches of milkweed and dogbane. These plants are common along meadows, roadsides and crops. Milkweed is considered a problem in fields because of its deep root systems and how easily it germinates.
Till idle land to prevent the milkweed from spreading. One tillage will kill seedlings if the plants are younger than 3 weeks old.
Apply the glyphosate according to manufacturer's instructions. Glyphosate is nonselective, so apply with caution. It kills any vegetation it contacts.
Continue scouting out milkweed populations and controlling them. It is best to apply the herbicide as the plant is in its late bud stage or when it's flowering.