Moths can be troublesome in a garden, not when they are winged adults but when they are caterpillars, their larval life stage. Caterpillars eat leaves, flowers and fruits of various crops; each kind of caterpillar has different food preferences. Unfortunately, getting rid of moths in a garden is a double-edged sword: Adult moths are beneficial pollinators of many flowering plants, some of which they ate when they were caterpillars.
Mix a few drops of liquid dish soap with warm water in a small bucket or bowl. Scour your garden for caterpillars and moth eggs, and collect them by hand. Drop them into the soapy water, and leave them in it for at least several minutes.
Handpicking, although effective, may be too time-consuming if the garden has a large caterpillar population. Ensure you don't accidentally remove beneficial insects' eggs. Moth eggs are typically small and vary in appearance by moth species. Many species lay their often cream- or white-colored eggs in small clusters on the undersides of plant leaves.
Screen Them Out
Attach fine-mesh screen around tomato cages by using cable ties, and place the cages over and around seedlings in the garden. An option to those screen covers is to use screen row covers and insect barriers, available at stores.
It's nice to open windows when the temperature is mild, but only if a fine-mesh screen keeps out insects. The same idea applies to screen covers in a garden. They allow vegetables to get wind, rain and sunlight but keep out moths and certain other insects.
Cut out the bottom of buckets or similar round, deep containers by using a saber saw or other cutting tool. Place each container around a seedling, and push several inches of each container into the ground. Inserting each container's lower portion below ground helps protect the seedlings from root-eating or overwintering caterpillars that live in soil.
- Mix 1 to 2 teaspoons of Bacillus thuringiensis var. kurstaki pesticide concentrate with 1 gallon of water.
- Put the mixture in a spray bottle.
- Spray the mixture over entire leaf surfaces of caterpillar-affected plants.
- Reapply the mixture every seven to 10 days as you see pests on the plants.
A naturally occurring bacterial organism, Bacillus thuringiensis var. kurstaki is an environmentally safe, effective and natural pesticide for caterpillars. The bacteria paralyze and disrupt caterpillars' digestive systems, causing the caterpillars to stop feeding within hours and die by starvation.
Remove Food Sources
Remove the garden's out-of-season crops that caterpillars eat. Doing so will help prevent the caterpillars from pupating and becoming adults.
For example, several kinds of caterpillars feed almost solely on cole crops (Brassica oleracea spp.) So when your curly kale (Brassica oleracea var. sabellica), broccoli (Brassica oleracea var. italica), cauliflower (Brassica oleracea var. capitata) and kohlrabi (Brassica oleracea var. gongylodes) have been harvested, remove those plants to prevent them from being food for caterpillars.