Nematode that liquefies harmful slugs will replace pesticides

By John Kessler

Two researchers from Oregon State University discovered a microscopic soil nematode. It can help fight against invasive slugs, which are very harmful to agriculture. The research results are published in the journals PLOS ONE and Biological Control.

The parasitic nematode, Phasmarhabditis hermaphrodita, can significantly reduce losses from invasive slugs. It has been used in Europe as a biological control product under the Nemaslug trademark for over 25 years but is not registered in the US with the EPA.

Scientists want to provide evidence that colonization of nematodes is a natural process. However, you first need to make sure that the nematodes do not have any effect on harmless local slugs or snails.

Farmers in the United States now rely on expensive slug control chemicals that are between 10% and 60% effective. In addition, pesticides affect non-target organisms and pollute waterways.

Finding the nematode was not easy. There are thousands, if not millions, of nematode species, and P. hermaphrodita “the size of a comma” is virtually invisible to the naked eye.

To find the nematodes, Rory J. Mc Donnell of the Department of Plant Science and Soil Science at Oregon State University and his collaborators set traps at the edges of agricultural fields in search of gray field slugs (Deroceras reticulatum) that might have died from the nematodes. Nematodes enter the slugs through a hole in the back of their mantle. Once inside, the nematode kills them, feeds on them and multiplies quickly. One nematode can produce about a thousand offspring within one to two weeks.

The gray field slug, which is a problem for both home gardeners and agriculture, is the most invasive slug species.

As they continue to work on P. hermaphrodita, Denver and McDonnell are growing other species to determine genetic relationships and possibly find related nematodes that can also be used as a “natural pesticide.”