New Zealand flatworm

Systematic position: Arthurdendyus australis is a species of flatworm belonging to the phylum Platyhelminthes, class Turbellaria, order Tricladida, and family Geoplanidae. Native to New Zealand, it has become a significant invasive threat in the UK, Ireland, and other temperate regions, disrupting local soil ecosystems.

Crops affected: This predator does not feed on plant tissue directly. Instead, it poses a severe threat to all crops and garden plants by consuming earthworms. As earthworms are essential for soil structure, drainage, and nutrient cycling, their disappearance caused by Arthurdendyus australis leads to soil compaction and reduced plant growth.

Biology and life cycle: It is a hermaphroditic species capable of self-fertilization. The flatworm lays distinctive, jet-black, shiny egg capsules that resemble blackcurrant seeds. These capsules are highly resilient and can survive for months in moist soil. The life cycle is strongly tied to humidity, with the worm hiding under stones, pots, or debris during dry periods.

Character of damage and harmfulness: The flatworm is an active hunter. It detects earthworms via chemical signals, engulfs the prey, and secretes enzymes that digest the earthworm externally. In infested gardens, earthworm populations can be decimated rapidly, which degrades soil aeration and reduces the availability of organic matter, significantly impacting overall garden productivity.

Control measures: There is currently no chemical pesticide approved for controlling the New Zealand flatworm without harming the wider environment. Integrated pest management focuses on:

• Strict biosecurity when importing plants or soil.
• Manual removal of adults and egg capsules found under debris.
• Maintaining well-drained, clear garden areas to limit suitable hiding spots.
• Monitoring vulnerable areas during damp, cool weather conditions.