Unlike many caterpillars that evolve into ornamental butterflies, the cutworm moth is as dingy and plain as its larvae. Several species of cutworm larvae plague North American organic gardeners, but you don’t need to distinguish one from another, as the control methods are the same for all species. Cutworm moths are nocturnal, and so are cutworm larvae.
Unless you’re out after dark, you won’t see these inconspicuous pests, but their damage is evident as seedlings chewed in half close to the soil level. Cutworms have smooth brownish or gray bodies and may have faint striping. They’re about the size of a nickel, and they curl up into a defensive position when disturbed.
Plastic Straws
If you have a small stand of flower seedlings you wish to protect, a time-consuming but effective method is fashioning a straw shield for each plant. Cut plastic straws into 2-inch pieces, and snip the pieces lengthwise. Slip a protective straw piece around the base of each seedling stem, inserting the lowest ½ inch of straw into the soil.
Cardboard Collars
If your seedlings are too large for drinking straw collars, use the cardboard tubes from toilet paper to make protective collars for your plants. Because the collars leave a margin of unprotected soil beside the plant, you may lose some plants to worms that get inside the tubes, but you’ll achieve at least 80% control.
Handpicking
If you’re a night owl, you can get out your flashlight at twilight and wait for hungry cutworms to emerge from the soil and mulch. Toss the worms into a bucket of soapy water, and add any nocturnal slugs or snails on your evening rounds as well.
Biological Control
Bacillus Thuringiensis, or BT, is a well-known biological control for all types of caterpillars. This organic powder paralyzes the intestinal tract of caterpillars when they begin to feed. Apply BT to the soil around the plants, rather than to leaves, to prevent killing the butterfly larvae you want to encourage. Reapply BT after it rains.
Parasitic Nematodes
If you’re experiencing a rainy spring season that prevents the use of BT, these conditions are optimal for parasitic nematodes. These beneficial nematodes live in the soil and appreciate moist conditions to help them migrate towards their prey. Steinernema carpocapsae and S. feltiaeare two commercially available nematodes that control cutworms.
Natural Enemies
Birds, ants, and parasitic wasps prey on cutworms in organic gardens. The action of these natural predators probably won’t give you the level of control you desire, but it’s important to remember that your chemical free garden works in harmony with nature to reduce pest populations. Plant sweet alyssum flowers to attract parasitic wasps and flies, and add a birdbath to attract avian friends.
Source:
Ohio State University Department of Entomology
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