Australoplana sanguinea

Australoplana sanguinea is an invasive species of terrestrial flatworm belonging to the order Tricladida and the family Geoplanidae. Native to Australia and New Zealand, this predator has been introduced to various parts of the world through the horticultural trade, where it poses a significant threat to local biodiversity and soil ecosystem services.

The organism primarily functions as a predator of earthworms and other soil-dwelling invertebrates. Its presence in horticultural environments is particularly damaging because it systematically eliminates earthworm populations, which are essential for maintaining soil structure, aeration, and nutrient cycling necessary for plant growth.

The biology of Australoplana sanguinea is characterized by hermaphroditic reproduction, where individuals produce resilient egg cocoons. These cocoons can survive for long periods in potting soil, making it easy for the pest to be transported between locations. The worms are nocturnal, preferring moist and dark conditions, and often hide beneath debris or within the root balls of container plants.

The damage caused by this flatworm is indirect yet severe. By drastically reducing the number of beneficial earthworms, Australoplana sanguinea causes soil compaction and degradation of the rhizosphere. This leads to stunted plant development and reduced resilience in vegetable, ornamental, and fruit crops, often mimicking symptoms of nutrient deficiency or drought stress.

To control the spread of this flatworm, strict biosecurity measures are required. Effective strategies include:

• Inspecting all incoming plant material and potting soil for signs of cocoons or worms.
• Removing garden debris, planks, and stones where individuals hide during the day.
• Manual removal and destruction of the worms when detected in the soil.

Chemical control is generally ineffective due to the physiological nature of flatworms and the risks of harming other soil biota. Integrated pest management, focusing on habitat modification and strict import regulations, remains the best approach to contain the infestation and protect the horticultural environment from this predatory threat.