HOST PREFERENCES OF THE BARK BEETLE POLYGRAPHUS PROXIMUS BLANDFORD (COLEOPTERA: CURCULIONIDAE: SCOLYTINAE) IN JAPAN DURING AN ENDEMIC POPULATION PHASE

Polygraphus proximus Blandford (Coleoptera: Curculionidae: Scolytinae) is anonaggressive phloem-feeding bark beetle native to East Asia. It has invaded European Russia and Western Siberia and is causing widespread fir forest mortality. However, little is known about host preference in its native range especially during endemic population phases. Thus, afield choice experiment was conducted at a study site where the P . proximus population phase was endemic to determine its host preference among fourAbies Mill. (Pinaceae) species native to Japan [ Abies firma Sieb. & Zucc., Abies homolepis Sieb. & Zucc., Abies sachalinensis (F. Schmidt) Mast., and Abies veitchii Lindl.]. This present study revealed that P . proximus preferred one of the study site's native host species, A . veitchii, whereas one of the study site's exotic host species, A . firma, was one of the least preferred species. Statistical analyses revealed a significant difference in host preference between the previous study conducted during the epidemic phase and the present study, suggesting that the beetle's population phases may influence their host preferences. The present study also suggests that an extended host preference during the epidemic population phase in P . proximus can cause extensive forest damage with further range expansions.