Hammerhead flatworm.
Photo: extension.msstate.edu.

Many people have greenhouses, and the environment in a greenhouse can support undesirable pests and diseases.

One such pest is the hammerhead worm (HW) or hammerhead flatworm or hammerhead slug (Bipalium kewense). Dr. Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service, shares this description about the hammerhead worm, “Hammerhead flatworms, a.k.a. shovelhead worms or arrowhead worms, are predators of earthworms and slugs which they track down, disable by covering them with slime, and consume by everting their ‘mouth’ over part of the earthworm’s body and digesting it. So far, there have been no indications of flatworms having any major adverse effects on earthworm populations in the US. Here in Mississippi, they are rarely very numerous, and they fare best in greenhouses or in the warmer, more southern portions of the state.

Like slugs, they are primarily active at night, or on moist, cloudy days, spending their days hiding in some dark, secluded space. This, and the fact that they just do not seem to be that common, is why they are so rarely encountered.” Dr. Layton shares that “They are harmless to plants.”

The Texas Invasive Species Institute (TISI) reports that this pest comes from southeast Asia. TISI links HW to “hot, humid environments, so it does well in greenhouses; in tropical and subtropical areas it can spread from greenhouses.” TISI also reports that HW is in Louisiana and other southern states.

However, TISI recommends “** When handling live flatworms please use gloves and hands should be washed in hot soapy water, and rinsed in alcohol or a standard hand disinfectant.**” If a greenhouse owner finds an HW, then care is needed to avoid contact because the secretions of HW contain a neurotoxin. Medicine.net defines a neurotoxin as “Any substance that is capable of causing damage to nerves or nerve tissue. For example, arsenic and lead are neurotoxins.” The reason black widow spiders are dangerous is because their venom is a neurotoxin.

TISI shares this unusual trait about HW, “…Reproduction seems to be primarily achieved through fragmentation: a small rear portion of the worm will pinch off, and "stay behind" as the worm moves forward. Within about 10 days, the head begins to form. This may happen a few times a month.” The “take home” message is to avoid chopping up an HW because the result would be more HWs.

For control of HW, Dr. Layton recommends, “To dispatch individual specimens, just sprinkle them with salt.”

If you want to contact Working in the Landscape, please send your questions and pictures to Keith Hawkins, Area Horticulture Agent (AHA), 337-463-7006 or khawkins@agcenter.lsu.edu. Also, you can be on the “commercial horticulture” email list by emailing your request to the address above.

“This work has been supported, in part, by the USDA National Institute of Food and Agriculture, Renewable Resources Extension Act Award, Accession Number 1011417.”