EPPO Global Database

EPPO Reporting Service no. 06 - 2014 Num. article: 2014/102

First report of Meloidogyne mali in the Netherlands: addition to the EPPO Alert List

The NPPO of the Netherlands recently informed the EPPO Secretariat of the first record of Meloidogyne mali on its territory. M. mali is a polyphagous species, originally described from Japan, which can produce large root galls and severely damage its host plants. Recent studies have showed that Meloidogyne ulmi, described as a new species from Ulmus chenmoui in Italy, was in fact a junior synonym of M. mali. In the Netherlands, M. mali was found in 2012/2013 on roots of several Ulmus trees of at least 50 years old in an arboretum in Wageningen, as well as in 3 experimental fields where trees were tested for their resistance to Ceratocystis ulmi (Dutch elm disease) in the municipalities of Wageningen and Baarn. It is noted that already in 1960, a root-knot nematode had been reported from elm trees at Baarn, but was associated at that time to M. arenaria (which presents morphological similarities). From February to March 2014, M. mali was also detected in several street trees at 4 different sites in the Hague. However, it is noted that M. mali was not detected during a survey conducted in 2013 in tree nurseries (50 sites were inspected and uprooted trees of Acer, Quercus, and Ulmus were inspected). It is suspected that
M. mali entered Europe via imports of elm rootstocks from Japan, at least 50 years ago. The following phytosanitary measures are being taken: a specific survey will be conducted in Ulmus and Malus nurseries, eradication actions will be considered if M. mali is found in nurseries, and an information campaign is being conducted to warn municipalities and tree nurseries about the risks posed by this nematode.
The pest status of Meloidogyne mali in the Netherlands is officially declared as: Present, limited distribution, actionable in case of findings at nurseries.

Meloidogyne mali
Why: Meloidogyne mali is a polyphagous root-knot nematode originating from Japan whose presence in the EPPO region has been noticed recently, although its introduction probably took place several decades ago. M. mali is a damaging nematode which can produce large root galls on its host plants, interfering with their water and nutrient uptake from the soil and thus reducing their growth. Taking into account the information presented in a preliminary risk assessment carried out by the Dutch NPPO, it was considered that M. mali should be added to the EPPO Alert List.

Where: M. mali was originally described in Japan from roots of an apple rootstock (Malus prunifolia). It has probably been introduced into the EPPO region with elm trees from Japan, at least 50 years ago.
EPPO region: Italy, Netherlands.
Asia: Japan (Honshu, Hokkaido).
In the Netherlands, M. mali was first found in 2012/2013 on roots of several Ulmus trees of at least 50 years old in an arboretum in Wageningen, as well as in 3 experimental fields where elm trees were tested for their resistance to Ceratocystis ulmi (Dutch elm disease) in Wageningen and Baarn. In 2014, M. mali was detected in several street trees in the Hague. In Italy, the nematode was first found on root samples collected during 1995-98 from slowly declining Ulmus chenmoui trees at San Rossore (Pisa, Toscana region). The nematode was initially described as a new species, Meloidogyne ulmi, which was later synonymized with M. mali. These elm trees had been imported from the Netherlands as 3 year old plants. Subsequently, populations of M. mali were found at Mantignano (Firenze, Toscana region) on U. chenmoui and U. glabra plants imported from the Netherlands and used as rootstocks of Ulmus hybrid selections. Although the presence of M. mali has only been confirmed in Italy and the Netherlands, it is thought that its distribution in the EPPO region might be wider because elm trees grown on the infected plots in the Netherlands (breeding programme for the resistance against Dutch elm disease) have been sent to other European countries.

On which plants: In Japan, M. mali is considered to be a significant pest of apple (Malus domestica/M. pumila, including rootstocks such as M. prunifolia) and mulberry (Morus alba, M. bombycis) trees. In Italy and the Netherlands, it has been found primarily on elms (U. chenmoui, U. glabra). According to the Japanese literature and experiments carried out in the Netherlands, M. mali has a wide host range which includes trees, shrubs and herbaceous plants (e.g. Acer palmatum, Acer pseudoplatanus, Arctium lappa, Brassica pekinensis, Broussonetia kazinoki, Broussonetia papyrifera, Castanea crenata, Citrullus lanatus, Cucumis sativus, Daucus carota, Dryopteris carthusiana, D. filix-mas, Fagus sylvatica, Ficus carica, Geranium robertianum, Geum coccineum, Glycine max, Impatiens parviflora, Maclura tricuspidata, Malus prunifolia, Malus sieboldii, Prunus x yedoensis, Quercus robur, Rubus idaeus, Solanum melongena, Sorbus aucuparia, Taraxacum officinale, Taxus baccata, Ulmus davidiana var. japonica, Ulmus x hollandica, Urtica dioica).

Damage: M. mali induces large root galls (‘bead-like’ galls) on its host plants resulting in malformed root systems and retarded plant growth. In Japan, stunting and severe decline has been reported in apple orchards infested by this nematode. Inoculation studies done in Japan on potted mulberry seedlings (Morus spp.) showed that 30 to 60% of the plants were killed by the nematode within a year. On 2-3 year old mulberry trees, inoculation resulted in a 10-20 % reduction of leaf weight. M. mali has sedentary endoparasitic habits. On apple, M. mali requires 18-22 weeks to complete its life cycle and there is one generation per year. It is suspected that the nematode overwinters in the roots (but the development stage at which this occurs needs to be studied).

Dissemination: natural spread in the soil is slow but M. mali can easily be transported with soil and plants for planting over long distances.

Pathway: Infested soil and growing media, plants for planting from countries where
M. mali occurs. Soil attached to machinery, tools, footwear, or plant products is also another possible pathway.

Possible risks: The host range of M. mali includes many species which are of economic importance in horticulture (e.g. apple) and forestry (e.g. elm). According to the Japanese literature, M. mali is an important pest in apple orchards. However, no data is available on its current economic impact on apple production. Its impact on vegetable crops (Brassicaceae, Cucurbitaceae, Solanaceae) and other major forest trees (Fagus spp., Quercus spp.) remains to be clarified but its potential capacity to develop on these economically important plants might add to the risk for the EPPO region. Once root-knot nematodes have been introduced into new areas, it is in general difficult to control or eradicate them. In its preliminary risk assessment, the Dutch NPPO underlined that M. mali presented a particular risk to tree species because of their retarded growth and their increased vulnerability to windthrow. The high cost of their replacement, either in orchards or in urban environments, was also underlined. Its seems desirable that more attention is given to M. mali, as its distribution in the EPPO region might be wider than originally thought, and to envisage possible measures to prevent its further spread.

EPPO RS 2014/102
Panel review date -
Entry date 2014-06


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