Parasitic Nematode Invading Elm Trees in Europe

A molecular investigation has revealed a new parasitic nematode that is invading trees in Europe.

Meloidogyne mali, as species is known, is now considered a synonym species of the nematode M. ulmi.

Researchers suspect this new nematode has been in the Netherlands for at least a half century.

M. mali is a nematode that is parasitic to plants. Scientists suspect it was introduced to the Netherlands during the breeding program on Elms against the Dutch Elm Disease (DED), when large number of elm rootstocks and seeds were imported from several different countries

The nematode affects its host by causing severe galling symptoms, which interferes with water and nutrient uptake from the soil.

In addition to the Netherlands, the nematode is expected to exist in ten other European countries namely Belgium, England, France, Ireland, Italy, Spain, Denmark, Germany, Slovakia and Romania, all of which were recipients of elms and elm seeds as part of the DED breeding program.

The first evidence of M. mali was reported in a 1969 in Japan. Through later studies it was associated with several plant species, including elm trees.

"During this study, M. mali was tested on some more plant species which were found to be hosts to this nematode species," the authors wrote in a statement. "It is highly probable that this root-knot nematode has even a wider host range than what is known now, and possibly a wider distribution in Europe than where it is currently confined to in Italy and the Netherlands."

The study is published in the journal Zookeys.