An analysis of the risk to the countries of the European Union from a possible introduction of Bursaphelenchus xylophilus and its vectors in the genus Monochamus is performed by assembling relevant biological, climatic and commercial information. The risks presented by different trade pathways are assessed and phytosanitary measures to reduce the risks are proposed. The conclusion of the PRA, based on EPPO PRA guideline no. 1, is that these pests present a serious risk to European coniferous forests.

Pest risk analysis (PRA) for the territories of the European Union (as PRA area) on Bursaphelenchus xylophilus and its vectors in the genus Monochamus.

Since the beginning of the 20th century, pine trees in Japan have been seriously damaged by the pine wilt disease. This disease is caused by the pine wood nematode, Bursaphelenchus xylophilus, which is transmitted by the Japanese pine sawyer, Monochamus alternatus. The control of disease depends to a large extent on chemicals, but the public is now demanding environmentally friendly control methods. The virulence of B. xylophilus varies very widely. Pre-inoculation of young pine trees in a nursery with avirulent B. xylophilus has induced systemic resistance of trees against a subsequent inoculation with virulent B. xylophilus. This induced resistance was considered a hopeful means for developing a biological control for the disease. The induced resistance by the avirulent nematodes was also expressed in mature pine trees in a forest where the disease was naturally epidemic. However, the effects of induced resistance were not satisfactory for practical biological control. Since the inoculation with higher concentrations of the avirulent B. xylophilus induced the resistance more effectively, the pre-inoculation method will need to be improved to develop the biological control. The induced resistance of pine trees by avirulent B. xylophilus should be one of the candidate biological control methods against pine wilt disease. This induced resistance also provides an experimental system to clarify physiological interactions between the nematodes and pine trees.

Pine wilt disease caused by the pine wood nematode: the induced resistance of pine trees by the avirulent isolates of nematode

Monochamus galloprovincialis Olivier (Col., Cerambycidae) is a vector of the pine wood nematode, Bursaphelenchus xylophilus, causing the destructive pine wilt disease. An effective lure for monitoring and/or mass- trapping would be of great interest in the management of this pine sawyer. Males and females of this species show an attractive kairomonal response to blends composed of four pheromone compounds used by Ips spp. bark beetles and two host volatiles from pines. This six-component lure is highly attractive but may to be too complex and costly for practical use as each component is released from a separate lure. The role of each component, ipsdienol, ipsenol, cis- verbenol, methyl butenol, a-pinene and ethanol as attractants for M. galloprovincialis was field tested in Spain to obtain a simpler but equally effective bait. Ipsenol was confirmed as the strongest kairomonal signal to M. galloprovincialis synergizing response to a-pinene by 95 times. The addition of methyl butenol to this blend doubled the number of males and females trapped. On the other hand, neither ipsdienol, cis-verbenol nor ethanol improved the results when incorporated into the above three-component blend. A lure consisting of ipsenol, methyl butenol and a-pinene may be very cost-efficient in operational monitoring or mass trapping of M. galloprovincialis. Three potentially repellent candidates, ())verbenone, methyl cyclohexenone and trans-conophthorin, were also tested against the attractive three- component bait. trans-Conophthorin significantly reduced male catches of M. galloprovincialis; methyl cyclohexenone had no effect. Verbenone significantly enhanced the response of females to the attractive combination of a-pinene, ipsenol and methyl butenol.

An operative kairomonal lure for managing pine sawyer beetle Monochamus galloprovincialis (Coleoptera: Cerymbycidae)

In 1984 a heavy Bursaphelenchus xylophilus infestation was observed in pinewood chips imported from USA and Canada into Finland Because there are good reasons to suppose that B xylophilus, if spread to pine forests in North Europe, can cause significant damage, the import of coniferous wood into Finland has been prohibited since autumn 1984 In surveys B xylophilus has not been found in roundwood or in chips imported from European countries into Finland Neither has B xylophilus been detected in Finnish pine trees around harbours nor in paper mills handling North American wood

Experiences with Bursaphelenchus xylophilus in Finland1

Summary Pine wood nematode, Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle, is the casual organism of pine wilt disease, a major tree killer in the Far East. This paper describes the biology of B. xylophilus, particularly its inter-relationships with vector insects in the genus Monochamus (Coleoptera: Cerambycidae), tree species and environmental conditions. The principal method of transmission, and hence of international plant health significance, is introduction of nematodes to susceptible dying or dead trees during female oviposition. This occurs in all countries where the nematode occurs but is the only significant method of transmission and survival of B. xylophilus in North America. Extensive tree mortality in Japan and China is associated with presence of highly susceptible tree species, suitable vector species and high summer temperatures. Pest risk assessments have been carried out to determine the risks to Europe; it is concluded that the nematode would undoubtedly survive in Europe but that tree mortality is likely only in the warmer southern countries. Methods to prevent transfer of nematodes to Europe are discussed in relation to European Union legislation.

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The pine wood nematode Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle (= B. lignicolus Mamiya and Kiyohara): an assessment of the current position

A review is given of historical aspects of the epidemic pine wilt disease and the associated control activities in Japan. Critical assessments of currently available control tactics, a summary of on-going research and an account of the prospects for integrated pest management of the disease are given. Research on the most appropriate application of direct control tactics are emphasized in this review, in addition to the necessity for long-term, intensive work on the environmental impact of chemicals.

T. Ikeda

Papers

Integrated pest management of Japanese pine wilt disease