The New Guinea Flatworm, scientifically known as Platydemus manokwari, is an invasive species that has spread globally through the movement of horticultural goods and soil. This predator’s presence causes significant concern due to its impact on native invertebrate populations. Control requires consistent, non-chemical methods to prevent further ecological damage. This article provides practical strategies for the eradication and management of this invasive organism.
Identifying the New Guinea Flatworm and its Ecological Impact
Correct identification is necessary before attempting any removal protocol, as this flatworm possesses distinct physical characteristics. The adult Platydemus manokwari is a long, narrow invertebrate, measuring between 1.5 to 2.5 inches in length and less than 2 millimeters thick. Its upper surface is a shiny dark brown or black color, featuring a faint, pale stripe that runs down the center of its back.
The underside of the flatworm is a pale grey to pinkish beige, and the head end is more pointed than the tail, possessing two small eyespots. This species thrives in environments with high humidity and is primarily nocturnal, making it less visible during the day. Homeowners most often encounter the flatworm in moist, dark microclimates, such as under potted plants, rocks, timbers, and leaf litter.
The need for eradication stems from the flatworm’s classification as one of the world’s 100 worst invasive species. It is a highly effective, generalist predator that feeds on a variety of invertebrates, with a particular preference for native land snails and earthworms. The flatworm uses a cylindrical, white pharynx to consume its prey, which has led to dramatic declines and even localized extinctions of native snail populations. Furthermore, the New Guinea Flatworm is a known paratenic host for the Angiostrongylus cantonensis nematode, commonly referred to as the rat lungworm, which poses a public health risk if the organism is accidentally ingested.
Non-Chemical Removal and Trapping Techniques
Due to the limited effectiveness and safety concerns of chemical pesticides, physical removal and trapping are the most effective control measures. Manual removal should always be conducted with protective gear, such as gloves and disposable tools, to avoid direct contact with the flatworm’s body and its potential toxic secretions. The best time for hand-picking is during the early morning, late evening, or after rainfall, as the nocturnal flatworm is most likely to be active and visible outside of its daytime refuges.
A highly effective method is the creation of simple, non-toxic traps that exploit the flatworm’s preference for dark, damp shelter. Laying a small piece of wood, a ceramic tile, or an overturned flower pot on the ground will create an attractive, moist hiding place. Placing these items in areas where the flatworms are suspected to be active will encourage them to congregate underneath during the day.
The traps should be checked daily, ideally mid-morning, by carefully lifting the cover and inspecting the underside for the flatworms. Baiting the traps can increase their efficacy, as the flatworms are drawn to the mucus trails of their prey, particularly snails. Placing a live snail or slug, secured under a fine mesh bag to prevent escape, can serve as a potent lure to draw the flatworms into the trap area. Once captured, the flatworms must be immediately transferred into a secure container using forceps. Never crush the flatworm on the ground during the removal process.
Safe Disposal Methods and Preventing Future Spread
Proper disposal is necessary because the flatworm’s body has the capacity for regeneration and can carry the rat lungworm parasite. Simply cutting or crushing the organism can release the parasite into the soil or allow body fragments to survive and grow into new flatworms. The most effective method is to kill the captured flatworms using extreme temperatures or a chemical solution.
One reliable technique is submerging the collected flatworms in a container of boiling water, which kills them instantly and prevents regeneration. Alternatively, they can be placed in a sealed plastic bag or container filled with rubbing alcohol, or frozen solid overnight before disposal. For infestations found directly in the soil of potted plants, soaking the entire pot in hot water (109 to 120°F or 43 to 49°C) for five minutes can eliminate the flatworms without damaging the plant roots.
Preventing the re-infestation and further spread of Platydemus manokwari is essential. The flatworm and its egg cocoons are often transported accidentally in soil, mulch, and potted plants. Thoroughly inspecting all new plants, soil, and gardening materials before introducing them to a garden or home is an important preventive measure.
Regularly cleaning gardening tools, footwear, and equipment after working in areas where the flatworm has been found helps prevent the accidental movement of the organism or its cocoons to new locations. Promoting good drainage and reducing excessive moisture in the landscape by eliminating piles of wood or leaf litter can also make the environment less hospitable to this invasive species.