Mint grows well as a perennial in most gardens, but the plants are prone to aphid infestations. These soft-bodied insects latch onto the underside of the mint leaves. The aphids pierce the foliage and suck out the sap. Their feeding eventually weakens the leaf so it turns yellow, curls up and begins to die. A severe aphid infestation may eventually stunt the growth of the plant or kill of the mint entirely. Controlling aphids with both manual and chemical methods destroys population of the pest.
Inspect the underside of the mint leaves for aphid symptoms. Aphids have green or black skin and cluster together in colonies on the leaf. Look for the honeydew, a sticky residue, left behind by aphid feeding.
Attach a sprayer nozzle to your garden hose. Adjust its setting to a sharp spray. Direct a spray of water at the infested mint foliage. The force of the water dislodges the aphids from the mints and washes them away. Spray removal controls minor aphid infestations.
Treat the mint with an insecticidal soap for more severe infestations. Spray the infested areas on the plants with the spray, following the manufacturer's application instructions. The soap coats the soft bodies of the aphids, inhibiting their breathing and killing the pests.