Mint’s (Mentha spp.) strong fragrance repels many pests, from ants to white cabbage moths, but a few pests do attack mint’s leaves and stems. Mints grow as perennials in U.S. Department of Agriculture plant hardiness zones 3 through 9, depending on the variety. Most of these pest infestations can be prevented with proper pruning and watering.
Tiny green or black insects, aphids attack the leaves of a plant, sucking out the plant sap. They can cause leaves to curl, pucker or turn yellow. An infestation can easily start when mint plants are overcrowded. A strong blast of water from the garden hose will remove aphids from your plants and weeding removes potential hosts for aphids.
Flea beetles are small, black, shiny insects that feed on leaves, causing holes and wilting. They cause most of their damage in spring and overwinter in leaf debris. Prevent infestations by cleaning up around mint plants at the end of fall.
Cutworms are the larvae of several different night-flying moths. The larvae live in the soil, causing the most damage in spring. They can kill mint plants by feeding on the stems at or below soil level. Pick of cutworms if you see them, and drop them into a bucket of soapy water to kill them. Keep mint plants weeded and till the garden in fall and spring to expose and kill the eggs before they hatch into cutworms.
Spider mites, which are about the size of a period or dot made with a pen, are related to spiders. They can become a problem during dry weather and attack the leaves of plants, causing white dots and yellowing on the leaves. They can sometimes kill the plant. Knock spider mites off the plants with a blast of water from the hose.
Insecticidal soap, which is considered less toxic than other insecticides, works by disrupting insects’ cellular membranes and causing the insects to dehydrate. It works best against small, soft-bodied garden pests, such as aphids and spider mites. To apply, mix 2 1/2 tablespoons of insecticidal soap with 1 gallon of water in a garden sprayer. Spray the solution on the mints, tops and undersides, in the early morning. Repeat this treatment every four to seven days or until the pest problem is eliminated. Rinse the mint thoroughly before you use it in the kitchen.