New Zealand flatworm

Systematic position: The New Zealand flatworm (Arthurdendyus triangulatus) is a member of the Platyhelminthes phylum, class Turbellaria, order Tricladida, and family Geoplanidae. It is an invasive predator that has become a significant concern for agriculture and soil biodiversity globally.

Biology and life cycle: It is a hermaphroditic species capable of self-fertilization. The flatworm reproduces by laying egg capsules that resemble black berries, which can persist in the soil for long periods. Adult worms can reach lengths of up to 17 cm, characterized by a flattened, sticky body and a distinctively pointed, triangular-shaped head.

Nature of damage and harm: The primary harm is not direct plant consumption but the systematic elimination of earthworm populations. By wrapping itself around an earthworm and secreting digestive enzymes, it liquefies its prey and consumes it. This leads to the loss of essential soil aeration and organic matter turnover provided by earthworms, causing long-term degradation of soil structure.

Crops affected: The impact is indirect but severe for all horticultural and agricultural crops. Without a healthy population of earthworms, soil compaction increases, drainage worsens, and nutrient cycling is significantly impaired, leading to poor plant growth and reduced vigor across a wide range of cultivated plants.

Control measures: There are currently no chemical pesticides approved for the eradication of Arthurdendyus triangulatus. Integrated management strategies are essential:

• Strict phytosanitary control of imported soil, pots, and nursery plants.
• Manual collection and destruction of observed flatworms, particularly after rainfall.
• Avoidance of moving moist soil or damp plant debris between different areas.
• Maintaining awareness in regions prone to high humidity to detect infestations early.