Cutworms are the larvae of several night-flying moth species (Order Lepidoptera, family Noctuidae). Cutworms are a common pest of a wide range of vegetable crops, including carrots, celery, lettuce, onion, tomato, pepper, eggplant, cole crops, rutabaga, beans, cucurbit crops, sweet corn, and others. Most cutworm species are solitary feeders found in the soil; however, some species occasionally attack the foliage and fruit of some vegetable crops.
Management of Cutworm in Radish
The Life Cycle of Cutworm
- The life cycle of cutworms in eggplant is similar to that of other plants. The female adult moth lays eggs on the underside of the leaves or stems of the eggplant plant. After a week, the eggs hatch into small larvae that begin to feed on the eggplant.
- The larvae will moult several times, growing larger with each moult. They will continue to feed on the eggplant until they are fully grown, which usually takes a few weeks.
- When the cutworms are fully grown, they burrow underground to prepare for the pupal stage. They will build a small pupal chamber in their borrowed space and begin developing into adult moths.
- Cutworms pupate for several weeks before emerging as fully formed adult moths. Once they have emerged from the pupae, they will mate and lay eggs, starting the cycle anew.
Factors Favoring Population Increase in Cutworm in the Field
- Mild winter temperatures and early spring warming
- Wet weather in the spring, which promotes plant growth and cutworm feeding
- The abundance of suitable host plants for feeding and egg laying
- Lack of natural enemies such as predators, parasitic wasps, and tachinid flies
- Reduced tillage practices leave more plant debris on the soil surface for cutworm larvae to hide in
- Over-fertilization of fields, which can increase plant growth and attract cutworms
Identification of Cutworm in Radish Field
- Cutworms have a smooth appearance with few hairs and curl into a tight ‘C’ shape when disturbed.
- Cutworms of various species can have distinct physical characteristics and colorations ranging from brown or tan to pink, green or grey, and black.
- Cutworms can be uniformly colored, spotted, or striped.
- Some cutworm larvae appear dull, while others appear glossy.
Damage Symptoms of Cutworm in Radish Field
- Clipped seedlings or leaves: Cutworms feed on seedlings and young plants by clipping them off at or below ground level. They also chew leaves that touch the ground, causing them to wilt or die.
- Multiple plants affected: Several plants in a row will often be wilted or clipped as cutworms feed on plants close together.
- Recurring damage: Cutworm damage often occurs in the same fields and parts of fields year after year.
- Damage at night: Cutworms feed mostly at night, and during the day, they are usually found just below the soil surface or under dirt clods.
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Management of Cutworm in Radish by Cultural Method
- Minimize egg-laying sites: Cutworms prefer to lay their eggs in weedy and overgrown areas. Keeping your garden clean and well-maintained can reduce the number of egg-laying sites.
- Till your land: Tilling the soil before planting and in the fall can help kill and expose overwintering cutworm larvae. This will also remove plant residue and discourage the laying of eggs.
- Use cardboard or aluminum foil collars: Placing collars around transplants can create a physical barrier that prevents cutworm larvae from feeding on your radish plants. Make sure to bury some of the collars under the soil and leave some above ground.
- Use trap crops: You can also plant crops like clover to attract cutworms away from your radish plants. This can help reduce the damage to your radish crop.
Management of Cutworm in Radish by Biological Method
- Use Bacillus thuringiensis var. kurstaki (Btk): Btk is a naturally occurring soil bacterium toxic to many species of caterpillars, including cutworms. It is available in OMRI-listed formulations approved for use in organic farming.
- Apply Btk according to instructions: Follow the instructions on the Btk product label for the appropriate application rate. Btk can be applied as a foliar spray or soil drench, depending on the infestation’s severity and the plant growth stage.
- Monitor your plants: Regularly monitor your radish plants for signs of cutworm damage. If you see any signs of damage, such as wilted or yellowing leaves or cut stems, apply Btk again to the affected areas.
Management of Cutworm in Radish by Chemical Method
- Chlorpyrifos, beta-cypermethrin, deltamethrin, and lambda-cyhalothrin are commonly used insecticides to control cutworm populations.
- Pre-planning application of insecticides may also be effective in controlling cutworms, but it is recommended only if large populations are expected.
Management of Cutworm in Radish by Organic/Natural Method
- Spinosad: Spinosad is a natural insecticide that works on cutworms and other pests without harming beneficial insects. Monterey Garden Insect Spray contains spinosad and can be purchased in pint, quart, or gallon-size containers. Mix it with water and apply it in the evening.
- Pyrethrins: Products containing pyrethrins, which are derived from chrysanthemum flowers, can be effective on cutworms. However, they should be applied when the larvae are young for maximum effectiveness. Monterey Take Down Garden Spray with pyrethrin comes in pint-size concentrate and 32-ounce ready-to-use containers.
Preventive Measures for Control of Cutworm in Radish Fields
- Chemical insecticides may be necessary to manage cutworm populations and prevent crop loss effectively.
- Cultural practices like crop rotation and sanitation can effectively reduce cutworm populations.
- Biological control methods, such as natural enemies and biopesticides like Bacillus thuringiensis, can also be incorporated into pest management plans.
- Chemical insecticides should be used only as a last resort when necessary and according to local regulations.
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Conclusion
Managing cutworms in radishes can be done using cultural and biological methods. Cultural methods include removing weeds and plant residue, minimizing egg-laying sites, using physical barriers, and planting trap crops. Biological methods include using Bacillus thuringiensis var. kurstaki (Btk) and understanding the limitations of natural enemies. Combining these methods and regularly monitoring your plants, you can effectively manage cutworms and prevent economic damage to your radish crop.
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