Dispersal of Monochamus galloprovincialis (Col.: Cerambycidae) as recorded by mark-release-recapture using pheromone traps

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 7-14days 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 250-532m and 2344-3495m 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 (0.57-0.76ha) or the seasonal sampling range (426-645m) 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.