Trapping strategy for Monochamus sutor and Monochamus galloprovincialis: potential vectors of the pine wood nematode in Scandinavia

The pine wood nematode Bursaphelenchus xylophilus is a threat to pine forests in Europe. Annual detection, and delimiting surveys if detected, are mandatory in the European Union. The trapping of Monochamus beetles, vectors of pine wood nematode, is included in both types of survey. The efficient use of traps increases the probability of detecting the pine wood nematode. How stand type, bait composition, wet or dry collecting jars, and trapping period during the summer affect the catches of Monochamus was investigated in central Sweden. Monochamus sutor and Monochamus galloprovincialis occurred together in half of the trapping locations, suggesting that the two species could interact as vectors for the pine wood nematode. Baited traps caught 25- to 30-fold more M. sutor than unbaited traps. Monochamus sutor was four- to seven-fold more abundant on clear-cuts than in pine stands, whereas numbers of M. galloprovincialis were similar in both habitats. There was no difference in catch between fresh and old clear-cuts for M. sutor. The addition of alpha-pinene to the pheromone baits increased catches of M. sutor by 1.6-fold on old clear-cuts, whereas there was no difference for M. galloprovincialis. Wet traps caught approximately two-fold more M. sutor than dry traps. Most M. sutor were caught in June and July, whereas the flight period of M. galloprovincialis started approximately 1 month later and peaked in July. Based on the results, a trapping strategy is presented for M. sutor and M. galloprovincialis in Scandinavia.