First Report of Bursaphelenchus xylophilus Associated With Pinus pinaster in France

The pine wood nematode (PWN), Bursaphelenchus xylophilus (Steiner and Buhrer 1934) is the causal agent of pine wilt disease (PWD), one of the most destructive diseases of pines worldwide (Abelleira et al. 2011). In the European Union (EU), PWN is classified as a priority quarantine organism under Commission Delegated Regulation (EU) 2019/1702. In the framework of official surveys conducted in France, PWN was detected in November 2025 in a wood sample taken in a private forest located in the southwest of the country. France is the third EU country in which PWN has been reported, following Portugal in 1999 (Mota et al. 1999) and Spain in 2008 (Abelleira et al. 2011). The wood sample was composed of a pool of chips taken from 15 Pinus pinaster trees located within a radius of 10 m in a forest stand in Seignosse (Landes department). According to the French analytical process (Mariette et al. 2023), this sample was split into two subsamples which were incubated at 25°C for 15 days. The first subsample was processed by the Oostenbrink dish method in the accredited Gironde Departmental Analysis Laboratory. DNA was extracted followed by real time PCR (François et al. 2007) on the obtained DNA. Amplification was performed using BsatF/BsatR/BsatS specific primers and a probe designed based on a sequence of the MspI satellite DNA family, and generated the expected 77-bp amplicon, indicating the presence of B. xylophilus. An analysis performed on the second subsample at the French National Reference Laboratory confirmed the positive status of the sample. For this purpose, the subsample was processed by the Oostenbrink dish method followed by an analysis coupling morphological identification and conventional PCR applied on isolated nematodes. This analysis highlighted the presence of 19 specimens of B. xylophilus, including four females and two males. The morphological characters of the adults conformed with those described for this species (Figure 1) and measurements of these specimens (Females: body length = 751.19 ± 105.61 µm, a = 33.44 ± 4.86, c = 22.60 ± 2.54, c′ = 3.05 ± 0.17, V = 72.20 ± 0.44, stylet length = 15.09 ± 1.61 µm; Males: body length = 779.49 ± 106.80 µm, a = 31.05 ± 4.60, c = 29.09 ± 3.20, c′ = 1.82 ± 0.01, stylet length = 15.15 ± 0.18 µm, spicule length = 24.41 ± 2.66 µm) were consistent with populations previously described by Mamiya and Kiyohara (1972) and Mota et al. (1999). The 13 juveniles detected in the second subsample were identified by a species-specific conventional PCR test (Matsunaga and Togashi 2004) targeting the ITS rDNA sequence. The amplified fragment obtained using XR/XF primers was 557 bp, confirming the specimens as PWN. The PWN outbreak led to the activation of an emergency plan, according to EU regulation (2012/535/EU) with the aim of limiting the spread of the nematode. The plan requires the control of wood movement in a demarcated area around the infested trees and the organisation of surveys to identify susceptible trees that are dead or dying. These diseased trees underwent official sampling for detecting PWN, following the analytical process described above. This subsequent sampling facilitated the collection of other PWN specimens which were then cultured on Botrytis cineara and can thus be used for further investigations. The authors wish to thank all the people involved in the French PWD monitoring programme, whether in coordination, inspection and field survey (local services of the French Ministry of Agriculture and their delegated agencies, including FREDON, agents of the DSF and their corresponding observers).