Cutworms

About this pest

Cutworms, those notorious nibblers of young seedlings, pose a significant threat to South African farmers and gardeners alike. Let’s delve into their world to understand their characteristics, why they’re pests, and how to combat them:

Physical Characteristics:

• Size: Typically 2-5cm long, but some species can reach 8cm.
• Colour: Brown, grey, or black, often with stripes or patterns for camouflage.
• Body: Soft-bodied, cylindrical larvae with smooth, waxy skin and prominent mandibles.
• Movement: Nocturnal, spending most of the day curled up in the soil and emerging at night to feed.

Common South African Names:

• Snywurm (Afrikaans): Cutting worm, another descriptive name.
• Grondwurms (Afrikaans): Ground worms, highlighting their habitat.

Why are Cutworms a Pest?

• Seedling destroyers: They sever young plants at the stem base, causing wilting and die-off, leading to significant yield losses.
• Wide range of crops: Attack a variety of crops, including maize, tomatoes, beans, lettuce, and tobacco.
• Difficult to control: Their nocturnal habits and burrowing behaviour make them challenging to target.

Combatting Cutworms:

Cultural practices:

• • • Crop rotation: Disrupts cutworm life cycles and reduces populations in specific fields.
    • Early planting: Gives seedlings time to establish before peak cutworm activity.
    • Tilling and ploughing: Exposes larvae and pupae to predators and sun, reducing their numbers.
    • Weed control: Eliminates food sources for adult moths and reduces egg-laying sites.

Physical barriers:

• • • Collars around seedlings: Made of cardboard or plastic, act as physical barriers.
    • Netting over vulnerable plants: Deters adults from laying eggs.

Biological control:

• • • Bacillus thuringiensis (Bt): A bacterium targeting caterpillars, safe for other insects and humans.
    • Beneficial nematodes: Parasitize and kill cutworm larvae in the soil.

Chemical control:

• • • Insecticides: Use registered insecticides as a last resort due to environmental impact and potential harm to beneficial insects. Focus on granular baits applied at dusk when cutworms are active.

Remember:

• Early detection and proactive measures are crucial to manage cutworm populations effectively.
• Monitor seedlings closely for signs of damage and the presence of larvae.
• Combine multiple control methods for a sustainable approach, prioritizing natural and organic strategies whenever possible.

By understanding the cutworm and adopting a comprehensive strategy, South African farmers and gardeners can protect their precious seedlings and secure a bountiful harvest.