The spread of the pine wood nematode (PWN), Bursaphelenchus xylophylus (Nematoda; Aphelenchoididae), the causal agent of the pine wilt disease, is greatly constrained to the dispersal of its vectors, long‐horned beetles of the Monochamus genus. Disease spread at global and regional scales has been mainly caused by human‐mediated transport, yet at a local scale, the short‐ and long‐distance dispersal behaviour of the beetles determine colonization dynamics. Three mark–release–recapture experiments using commercial traps and lures allowed the parameterization of the dispersal kernel under two landscape fragmentation scenarios for the only known European PWN vector, Monochamus galloprovincialis. The respective release of 171 and 353 laboratory‐reared beetles in continuous pine stands in 2009 and 2010 resulted in 36% and 28% recapture rates, yet, at a fragmented landscape in 2011, only 2% of the released 473 individuals could be recaptured. Recaptures occurred as soon as 7–14 days after their release, in agreement with the requirement of sexual maturation to respond to the pheromone–kairomone attractants. Data from the first two experiments were fitted to one mechanical and two empirical dispersal models, from which the distance dispersal kernels could be computed. Derived estimated radii enclosing 50% and 99% of dispersing M. galloprovincialis under continuous pine stands ranged between 250–532 m and 2344–3495 m depending on the replicate and choice of model. Forecasted recaptures in 2011 resulted in a moderate underestimation of long‐distance dispersal, probably influenced by the high degree of habitat fragmentation. In addition, trapping parameters such as the effective sampling area (0.57–0.76 ha) or the seasonal sampling range (426–645 m) could be derived. Observed results, derived dispersal kernels and trapping parameters provide valuable information for the integrated pest management of PWD. Furthermore, estimated dispersal distances indicate that ongoing clear‐cut measures for eradication in the European Union are likely ineffective in stopping the vectors dispersal.
Monochamus galloprovincialis Olivier beetles vector the causal agent of pine wilt disease (PWD), nematode Bursaphelenchus xylophilus (Steiner and B€ uhrer) Nickle, in Europe. Traps and attractants have been optimized for the capture of M. galloprovincialis, increasing the possibility of developing methods of lowering its population in PWD-affected areas with the aim of either eradicating the disease or containing the spread of it. To evaluate the effectiveness of such mass-trapping campaigns, two sets of experiments were carried out in 2010 and 2013. The release of 353 laboratoryreared beetles in the experimental area of 2010 facilitated the evaluation of capture-mark-recapture (CMR) procedures in the calculation of population abundance estimates using the POPAN formulation of the Jolly-Seber model, a prerequisite for the assessment of mass trapping. Abundance estimates derived from best-fitting parameters fell within one standard error of the real figures, proving the method appropriate. In 2013, four trap densities were tested in six 36 ha plots. To evaluate the removed proportions, the local beetle population was estimated in a contiguous 260 ha study area. A superpopulation of 21 319 individuals could be calculated from the CMR data, corresponding to a rough density of 82 individuals per hectare. Evaluated trapping densities removed 4.66%, 20.50%, 33.33% and 59.80% of M. galloprovincialis population at 0.02, 0.11, 0.25 and 0.44 traps/ha, respectively, thus the estimated 95% removal would occur at 0.82 traps/ha. These results suggest that substantial reduction of M. galloprovincialis abundances might be achieved via mass trapping and that this represents a very promising management method for the containment or eventual eradication of B. xylophilus at the areas affected by the PWD.
Transmission of the causing agent of the pine wilt disease, Bursaphelenchus xylophilus (Steiner & Buhrer) (Nematoda: Aphelenchoididae), among Pinus pinaster Aiton (Pinaceae) trees in Portugal is known to occur during pine sawyer, Monochamus galloprovincialis (Olivier) (Coleoptera: Cerambycidae), adult feeding on twigs of healthy trees or during female oviposition on dying or dead trees. Still, the disease does not affect the other potentially susceptible local pine species, Pinus pinea L. Several experiments evaluated the suitability of P. pinea as a host for M. galloprovincialis feeding, oviposition, and progeny development. Feeding responses were studied in two-choice experiments pairing P. pinea twigs with P. pinaster, Pinus halepensis Miller, Pinus sylvestris L., Pinus uncinata Miller, and Pinus nigra Arnold. Another test assessed the effect of increased dosages of limonene applied to P. pinaster twigs on M. galloprovincialis feeding. Oviposition preferences for P. pinaster, with either intact or manipulated bark thickness, P. pinea, and P. sylvestris were also studied in two-choice tests. Finally, suitability of P. pinea as a substrate for the development of M. galloprovincialis offspring was tested. Results showed that P. pinea could be an acceptable host for the pine sawyer feeding under laboratory conditions. Only P. sylvestris and P. pinaster twigs were significantly more consumed than those from P. pinea. Control and limonene-treated twigs were eaten similarly, but feeding decreased as dose increased, suggesting an inhibitory effect of limonene. Oviposition wounds, both eggcontaining and eggless, occurred more on P. pinea than on P. sylvestris or P. pinaster, though the percentages of wounds indicating successful egg laying were significantly higher on P. pinaster and P. sylvestris. Monochamus galloprovincialis progeny completed its development on P. pinea, but emergence was lower than on P. sylvestris, likely due to higher mortality during egg and early larval stages. Thus, results on vector host preferences do not explain the observed absence of nematodekilled P. pinea trees in the field.
Novel associations between exotic pathogens and native insects may result in major ecological and economical losses. In Europe, Monochamus galloprovincialis (Olivier) (Coleoptera: Cerambycidae) is the only known vector of the exotic pine wood nematode Bursaphelenchus xylophilus (Steiner & Buhrer) Nickle (Nematoda: Aphelenchoididae), the causal agent of pine wilt disease (PWD). Transportation of goods containing nematode-infested beetles is the main pathway for the spread of the disease. In this scenario, management actions involving early detection and eradication are critical to stop further spread by the vector. Although dispersal of mature M. galloprovincialis has been successfully tracked using commercial baits and traps, dispersal ability of immature individuals is poorly understood. Sexual maturation and other physiological traits related to dispersal were studied for newly emerged M. galloprovincialis after different shoot-feeding spans. Sexual maturation was complete after on average 12 (males) or 13 (females) feeding days. Monochamus galloprovincialis adults emerged with an average of 10% lipid and 23.8% (males) or 29.9% (females) pterothorax muscle content, and these percentages did not change significantly during shoot feeding. Microtomography images of wing muscle structures at different maturation stages confirmed these results. Emerged adults that were kept unfed survived an average of 12 days in the lab. The ability of unfed immature insects to fly through hostless terrain was studied by marking and releasing newly emerged insects from a crop area located up to 3 km away from two small pine stands. The longest flown distance recorded was 2 km. Fitted regressions indicated that immature insects could have travelled up to 3 109 m to reach the experimental stands. We found that M. galloprovincialis emerge with welldeveloped thoracic muscles and energy reserves that enable them to sustain long flights over nonforested areas. These findings should aid managers and policy makers in devising sound procedures in areas where the risk of introducing PWD is high.
La actividad humana ha estado muy ligada al movimiento ya sea intencionado o fortuito de organismos vivos exóticos que ponen en serio peligro nuestros ecosistemas. Un importante caso que afecta a nuestros bosques fue la introducción del nematodo del pino Bursaphelenchus xylophilus (Steiner and Buhrer) Nickle (Nematoda: Parasitaphelenchidae) causante de la más importante enfermedad que está destruyendo actualmente nuestros pinares: "la enfermedad del marchitamiento del pino". Este organismo originario de América fue accidentalmente introducido en Asia en 1905 (Yano, 1913) donde ha causado daños devastadores en sus pinares originando pérdidas millonarias (Yoshimura et al., 1999). En 1998 fue detectado por primera vez en Europa en la península de Setúbal, Portugal (Mota et al., 1999). Los primeros estudios demostraron que el único vector en Portugal es el perforador de los pinos Monochamus galloprovincialis Olivier (Coleoptera, Cerambycidae), insecto que se encuentra distribuido por toda Europa, Cáucaso, Siberia, Mongolia, China y el norte de África. Ambos, B. xylophilus y sus vectores, se clasificaron como un organismo de cuarentena de la clase "A-1" (OEPP / EPPO 1986).
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