Perilla Mint-Potentially Deadly Weed

Perilla Mint is fairly common in some areas of NC. It can be particularly problematic in late summer and early fall when it has developed seeds. It is toxic to all species of livestock. Like many toxic plants, animals usually do not eat Perilla Mint, but if pasture conditions are poor and forage availability is low, animals may become more interested in browsing forbs. Such was the case on a cattle farm in eastern NC recently, when cattle were given access to a shady lot that had not been grazed in several years. There was an abundance of this weed in that area, and the cattle seemed to selectively browse those plants. As a result, 8 head were lost. Necropsy results indicated interstitial pneumonia, consistent with damage caused to the lungs by the toxins in Perilla Mint.








Perilla Mint is a warm-season annual broadleaf plant. There are several identifying characteristics of this plant. One of the most indicative is a square-shaped stem, that is sometimes green but often purple, particularly the lower portions of the stem. Leaves are roughly egg-shaped and coarsely serrated along the margins, and have a strong minty odor when crushed.

Animals affected by Perilla Mint exhibit respiratory distress and are usually reluctant to move. In fact, moving these animals can add to the stress, bringing on death more quickly. Therefore, prevention is key in dealing with this potential toxin. Scout pastures, particularly shaded areas in and near woods for this plant. If it is found in small quantities, the best course of action may be pulling the plants up and removing them from the pasture. In larger quantities, mowing or spraying may be justified. Care should be taken, however, to exclude animals from the area until the plants are thoroughly broken down, as this can increase their curiosity about the plant and could lead them to try it. Contact your Extension Agent for herbicide recommendations for this and other weeds, and always follow label instructions when applying any pesticide.

Because this plant is an annual, if you find it this year you will likely have it again next year. Take note of locations where you find this plant and be ready to initiate control methods next year in late spring or early summer when the plant is easier to control. Take efforts to maintain an adequate supply of desirable forage for animals to decrease the possibility they will browse this or other undesirable plants.

The University of Tennessee has an excellent article on identifying Perilla Mint and managing livestock in those areas. While this article mentions cattle particularly, remember that all animals can be affected.
https://extension.tennessee.edu/publications/Documents/W135.pdf

 Please remember that any control methods recommended in the linked article are for the state of Tennessee. Please contact your Extension Agent for control methods specific to your state and area.