Long‐term survival and non‐vector spread of the pinewood nematode,Bursaphelenchus xylophilus, via wood chips

Abstract

Summary The pinewood nematode, Bursaphelenchus xylophilus, is the causal agent of pine wilt disease and is transmitted to new host trees by beetles of the genus Monochamus. The increasing interest in imported wood chips from North America for paper production and energy purposes and the corresponding phytosanitary risk of non‐vector transmission of B. xylophilus has been discussed since 1984, the year of the first interception of B. xylophilus in wood chips in the European Union. The long‐term survival of B. xylophilus in wood chips and its non‐vector spread from infested wood chips to non‐infested trees were studied. Pinus sylvestris logs were inoculated with a suspension of B. xylophilus to produce infested wood chips. During the long‐term storage test, B. xylophilus in P. sylvestris wood chips were examined. Four variants, including sealed and openly stored wood chips at both 15°C and 25°C, were studied. For the test of non‐vector spread, B. xylophilus ‐infested wood chips were placed on three‐ to four‐year‐old P. sylvestris saplings under different conditions. Bursaphelenchus xylophilus survived for more than 1 year at both temperatures in the sealed wood chips, which was significantly longer than for the openly stored variant at 25°C. Temperature, tree condition and wood chip location all influenced non‐vector spread through wood chips. Of the 480 trees that were in contact with infested wood chips and showed clear symptoms of pine wilt disease, B. xylophilus were extracted from 42 pines at 25°C and one pine at 15°C. The highest B. xylophilus infestation rates resulting in clear pine wilt disease symptoms (75%) were found in infested wood chips directly attached to stem‐wounded trees at 25°C. However, more variants exhibited B. xylophilus infestation at this temperature; trees with stem or root injuries plus direct contact with infested wood chips to the wounded part were primarily affected. Moreover, non‐vector spread was also detected in stem‐ and root‐injured pines without any direct contact with infested wood chips. Our results confirmed that B. xylophilus can survive for long periods in wood chips and can be transmitted from infested wood chips to damaged trees, but the likelihood of such PWN establishment should be low compared to spread through vectors. These findings must be considered in the pest risk analysis of B. xylophilus, and studies using outdoor trials should be carried out to complete this pest risk analysis.

Common pathways by which non-native forest insects move internationally and domestically

“…For instance, wood chips are recommended to be less than 3 cm in at least two dimensions, but the ideal size will vary depending on the intended use (IPPC 2017a). Many countries require coniferous wood chips to be treated because they could contain pinewood nematode, Bursaphelenchus xylophilus (Parasitaphelenchidae; Allen et al 2017;Hopf-Biziks et al 2017), although similar regulations are mostly lacking for hardwood chips (Flø et al 2014).…”

Calentamiento por radiofrecuencia para esterilizar Pinus radiata como material para embalajes. Parte 1: Tiempo total de tratamiento

“…La madera para embalajes de Pinus radiata requiere ser esterilizada de acuerdo con las normas fitosanitarias internacionales (FAO 2013). El principal riesgo fitosanitario para la madera son las plagas cuarentenarias tales como el nematodo del pino Bursaphelenchus xylophilus (Steiner and Buhrer 1934, Mamiya 1983, Dwinell 1997, Haack et al 2011, Hopf-Biziks et al 2017. El calentamiento con vapor es usualmente utilizado para esterilizar con calor la madera verde de Pinus radiata para embalajes de exportación (Ananias et al 2015).…”

PM 3/87 (1) Monitoring and consignment inspection of wood chips, hogwood and bark for quarantine pests

“…If wood commodities with pinewood nematode are placed next to a host tree there is a theoretical risk of direct transfer from the chips/hogwood to the host, as demonstrated in a laboratory environment by Hopf‐Biziks et al . (). The risk was found to be higher when (i) the host was injured in some way, (ii) there was direct contact with host trees and (iii) the temperature was higher (25°C as opposed to 15°C).…”