Identification and Control of Mint Pests
Neem Oil , horticultural oil, insecticidal soap or garlic oil will help control white fly populations. Horticultural oils and insecticidal soaps will smother them at any life stages.
Try to avoid pesticides for white flies, many strains are resistant, but their predators and other beneficial insects such as pollinators are not. Spray with Broad-spectrum insecticides, such as Pyrethin only as a last resort.
Green Fruit worms Named "Green" Fruit worms, not only because they are green, but because they primarily feed on Green or immature Fruit they are most commonly called inch worms.
If you only have a small crop of mint growing, handpicking will generally suffice. If you have a large crop and / or the worms are feeding on other plants in your garden consider using Bacillius thuringiensis[BT]. BT should be applied at either bloom or petal fall, or both. It is not generally harmful to beneficial insects. It is a stomach poison and must be ingested, it is effective when applied during warm, dry weather while the larvae are actively feeding. Requires more than 1 treatment.
Cut Worms are the larvae of a group of dull-colored , night-flying moths of several different species. They are often visible around lights in Spring, They come in various colors, but are generally a dull gray and well camouflaged within the soil.
Cutworm larvae chew young plants off at the base at or near ground level. When you see a freshly severed plant, carefully stir the soil around it and you can usually find and destroy the culprit before it can move to the next plant.
Bacillius thuringiensis [BT] is effective. Apply it to the soil in the affected area at either bloom or petal fall, or both. It is most effective when applied during warm, dry weather while the larvae are actively feeding. As cutworms are nocturnal an early evening or late afternoon application is best. There are several inexpensive methods of controlling cutworms see our article Identification and Control of Cutworms.
Snails and Slugs are not generally a major problem, but they have been know to chow down on some types of mint See: Slug and Snail control.