Watch YouTube Video on the Biological control of Cutworms.
Introduction
Cutworms are notorious garden and crop pests that can destroy seedlings overnight. Instead of relying on chemical pesticides, many growers are turning to biological control of cutworm, a safer and more sustainable alternative. In this guide, we’ll explore how natural predators, parasites, and beneficial nematodes can help keep cutworm populations under control.
What Are Cutworms?
Cutworms are the larval stage (Photo 1) of several species of night-flying brown or tan, banded moths (Photo 2). These thick, soft-bodied caterpillars hide in the soil during the day and feed at night, cutting young plant stems at ground level (Photo 3). Their damage is especially devastating in vegetable gardens and row crops.
Why Choose Biological Control?
Biological control focuses on using natural enemies to regulate pest populations as they are:
- Environmentally friendly
- Safe for humans, pets, and pollinators
- Effective for long-term pest suppression
- Compatible with organic farming
Top Methods for Biological Control of Cutworm
1. Beneficial Steinernema and Heterorhabditis Nematodes
Beneficial Steinernema carpocapsae and Heterorhabditis bacteriophora nematodes (Photo 4) are microscopic, soil-dwelling roundworms that act as powerful natural enemies of cutworms. These nematodes are widely used in organic gardening and sustainable agriculture because they target pests in the soil without harming plants, people, or beneficial insects. When applied to moist soil, nematodes actively search for cutworm larvae by detecting chemical cues emitted by the cutworm larvae.
Once they locate a cutworm larvae, they enter the body cavity of larva through its natural openings such as the mouth, spiracles, or anus. Inside the larva, the nematodes release symbiotic bacteria, mainly Xenorhabdus spp. and Photorhabdus spp., which are typically associated with Steinernema and Heterorhabditis nematodes, respectively. These bacteria multiply rapidly and cause septicemia, killing the cutworm within 24–48 hours. As the larva dies, its body becomes a suitable “nutrient capsule,” allowing the nematodes to feed, reproduce, and release new generation infective juvenile nematodes that continue hunting for additional pests in the surrounding soil.
Nematode Application Tips
For effective control of cutworms, apply 25,000 nematodes per square foot area with a watering can (Photo 5) in the early morning or late afternoon to prevent UV exposure, which can kill them instantly. Water the soil before and after application to maintain moisture as nematodes need moist environments to move. Apply nematodes repeatedly every 2–4 weeks during heavy infestation periods for best results. Store nematodes in a refrigerator and apply before the expiration date for maximum activity.
2. Natural Predators of Cutworms
Several beneficial predators feed on cutworms and can drastically reduce their populations.
Key Predators:
- Ground beetles (Carabidae) (Photo 6)
- Birds such as robins and blackbirds (Photo 7)
- Parasitic wasps (such as Trichogramma spp.) that target moth eggs
- Spiders (general predators) (Photo 8)
- Assassin bugs (Photo 9)
How to Attract Natural Predators
Plant flowering borders to provide nectar (Photo 10). Avoid broad-spectrum pesticides. Provide mulch, leaf litter, and small habitat areas.
3. Microbial Agents: Bacillus thuringiensis (Bt)
Bacillus thuringiensis var. kurstaki (Bt) is a natural bacterium widely used in organic farming. It specifically targets caterpillars, including cutworms.
Advantages:
- Safe for people, pets, and beneficial insects.
- Breaks down quickly in sunlight and has no long-term residue.
- Highly effective on young larvae.
Conclusion
The biological control of cutworms offers a powerful, eco-friendly alternative to chemical pesticides. By harnessing beneficial nematodes, natural predators, and microbial agents like Bt, gardeners and farmers can protect their crops sustainably. Whether you manage a home garden or a large farm, these natural solutions help maintain healthy soil, strong plants, and a thriving ecosystem.