As we get into the heat of summer, it is time to be on the lookout for a highly toxic plant, perilla mint, in pastures. Perilla mint is often found in the shaded areas of pastures, particularly along the edges. As a member of the mint family, perilla mint has a distinctive square stem. The leaves are large, broad, serrated, and oppositely arranged with a purplish coloration on the underside of the leaf. The plant grows upright and will put on a 6 inch long spike of purplish flowers. While all parts of the plant are toxic to livestock, the flowers are the most toxic part of the plant. Perilla mint flowers between July and September, which is also when cattle tend to congregate in shady areas where the plant is found, posing a danger of ingestion. Cattle will typically leave perilla mint alone when there is plenty of forage available, but when forage is limited due to drought, there is a danger of cattle grazing the plant. When the plant is ingested, it causes respiratory distress and death in cattle.

There are several herbicides available that provide effective control of perilla mint. It should be noted that once the plant begins to wilt after spraying, it becomes more attractive to livestock, so animals should be kept away from treated areas. Post-emergence chemicals that control perilla mint include picloram, aminopyralid, 2,4-D, glyphosate, and dicamba. As always, follow the labeled instructions when applying pesticides.

For more information contact LSU AgCenter County Agent Randall Mallette in Natchitoches at 318-357-2224, or in Coushatta at 318-932-4342.

Shared by Randall Mallette, Associate Extension Agent