Express PRA on Massicus raddei
M. raddei has hosts in the genera Quercus, Castanea and Castanopsis. It has caused epidemic outbreaks in several provinces of Northeast China (Jilin, Liaoning and adjacent areas in Inner Mongolia) on Q. mongolica and Q. liaotungensis. Such outbreaks occur only in a small part of its wide distribution in Asia. Limited or no data was found on the situation and impact on other hosts, or in other areas where the pest occurs (i.e. many other Chinese provinces, as well as Japan, Far-East Russia, Korea Rep, Korea Dem. Rep., Vietnam).
For all pathways, entry would depend on very specific conditions, which would probably be fulfilled only for a small part of the trade (especially trees should have a diameter at breast height (DBH) or bonsai base diameter >9 cm). The likelihood of entry was considered moderate for host plants for planting, wood packaging material (if ISPM 15 is not applied) and firewood (as round wood). For plants for planting, the EWG thought there would be relatively few trees of a sufficient DBH or diameter imported from Asian countries where M. raddei could occur. Regarding wood commodities, the likelihood of entry, especially on round wood, was reduced because of the ban on logging in areas of outbreaks in Northeast China. Round wood is otherwise highly favourable to allow entry of the pest from biological considerations. The assessment would change if the ban was lifted. Round wood (with or without bark, other than firewood), wood chips >2.5 x 2.5 cm in two dimensions, hogwood and processing wood residues, as well as furniture and other objects made of wood, presented a low risk of entry. Hitchhiking also presented a low risk. Finally, hitchhiking presented a low risk of entry.
Establishment of M. raddei is likely to occur in the EPPO region and would not be limited by climatic conditions (although there is a high level of uncertainty for warm and arid areas in North Africa, the Near East and Central Asia). Quercus and to a lesser extend Castanea are widespread in the region. Although the host status of European species is not known, M. raddei has many Castanea and Quercus hosts. It has hosts in both subgenera of Quercus (Cyclobalanopsis and Quercus), and in the 3 sections of the subgenus Quercus that are present in Asia (out of 5, the remaining 2 being North American). It is reported on 4 Asian Castanea species (out of 9 in total, others being C. sativa and 4 North American species) (www.theplantlist.org). M. raddei is believed to present a higher risk of host switch (i.e. to European species) than a pest that attacks only species from one section (such as Agrilus auroguttatus (Coleoptera: Buprestidae) on white oaks). It is therefore assumed that it would be able to use some other Quercus and Castanea species as hosts. There are non-supported statements regarding non-Fagaceae hosts in the literature (section 7, Table 3), which would increase the risk if confirmed.
The likelihood of spread was rated as moderate because natural spread will be slow, but there may be long distance spread with commodities that would lead to multiple outbreaks and increase the spread.
The potential impact in the EPPO region is uncertain, but would probably be lower than that registered in areas of epidemic outbreaks in Northeast China. The potential impact would depend on the oak and chestnut species that are susceptible, especially if Castanea sativa or major Quercus spp. in the EPPO region are hosts. If only the currenly known hosts are attacked, damage would mostly be limited to ornamental hosts (noting that those are probably not very widely used), and to C. crenata where it is cultivated or present in the wild. In addition, considering the wide distribution of M. raddei in East Asia, significant damage is only reported in a small part of that area.
Because of the severe outbreaks in Northeast China, of the importance of oaks and chestnuts in the EPPO region, and of the potential impact, the EWG considered that phytosanitary measures should be recommended.
Phytosanitary Measures to reduce the probability of entry: Risk management options are considered for plants for planting of Castanea, Quercus and Castanopsis; wood of Castanea, Quercus and Castanopsis, wood chips, hogwood, processing wood residues; wood packaging material; furniture and other objects made of wood of host plants.
2021: This PRA document was modified to clarify the phytosanitary measures recommended
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