Optimizing trap placement for monitoring Monochamus galloprovincialis and minimizing bycatch of beneficial insects

The pine sawyer beetle Monochamus galloprovincialis is the only known vector of the pine wood nematode (PWN) in Europe. Pheromone traps are one of the tools used for monitoring M. gal- loprovincialis and PWN. Numerous studies have been conducted to improve trapping efficiency, but the effects of habitat type and trap exposure in relation to forest have received the least attention. Bycatch of non-target species has also been rarely considered. The aim of this study was to evaluate the effects of (1) site type such as forest interior, forest edge, and open field adjacent to forest, (2) open field type (clear-cut or plantation), (3) trap location (west or east) relative to the forest on catches of M. galloprovincialis and selected non-target insect species. The study plots were established in 86-91 years old Scots pine stands and adjacent open fields. White, PTFE- -covered, cross-vane traps baited with Galloprotect Pack lure were used for insect capturing. Site type had a significant effect on catches of M. galloprovincialis and 14 non-target species. M. galloprovincialis, Hylurgus ligniperda, Spondylis buprestoides, and Prionychus ater were most abundant at the forest edge. Catches of three longhorn beetles (Acanthocinus aedilis, A. griseus, and Arhopalus rusticus) and three predatory species (Thanasimus formicarius, T. femoralis, and Corticeus pini) had a decreasing trend from the forest interior towards the open field. The opposite was observed for Chalcophora mariana, Phaenops cyanea, Magdalis violacea, Cardiophorus ruficollis, and Pseudocistela ceramboides. The west side of the forests was significantly preferred by M. galloprovincialis (females) and Ph. cyanea, while it was avoided by S. buprestoides, both Thanasimus species, and C. ruficollis. The type of open field had a significant effect on catches of seven non-target species but not on M. galloprovincialis catches. Possible causes of the observed patterns in insect catches are discussed. In summary, for efficient monitoring of M. galloprovincialis with reduced bycatch of beneficial insects traps should be deployed at the westerly exposed forest edge. This trap location can also be recommended for catching higher numbers of forest pests such as Ph. cyanea and H. ligniperda and minimizing bycatch of predatory beetles. Furthermore, trap placement a few meters from the tree line should reduce the probability of bark damage for oviposition and eventual PWN transmission to healthy trees by M. galloprovincialis females attracted to the traps.