Abstract:

Objective: Liquidambar styraciflua, north American sweetgum tree is a new important exotic ornamental foliage tree that is widely used in urban areas of eastern China. To provide information for prevention and control of a new bark beetle pest, Acanthotomicus suncei, which damages north American sweetgum, we described morphological characteristics of the bark beetle and its biological characteristics as well as its occurrence status in Shanghai and adjacent regions. Method: We collected information of its biology and occurrence through field investigation. The proventricule and male genitalia of the beetle specimens were collected from host trees in the field. A stereo microscope was used to observe the morphological characteristics. The difference in the morphological characteristics from all known Acanthotomicus species in China were compared. Result: A. suncei has distinct identification characteristics. The placement of four elytral declivital spines arise on interstriae 2, 4, 6, and 8. Lateral tibiae of both foreleg and midleg have 4 dentations respectively, and the declivital spines of females are smaller than males. The differences in morphological characteristics from the three known Acanthotomicus species in China were significant. The length of A. perexiguus is less than 2 mm, with 3 pairs of declivital spines. A. spinosus carries 8 pairs of declivital spines while the length is similar with A. suncei. The beetle has 2 to 3 generations per year in Shanghai. The larvae feed on cambium and phloem in the trunk, causing rapid death of the host trees. It was found that 14 planting sites of American sweetgum were infested by A. suncei and more than 30 000 trees died from the beetle feeding under nurseries, parks or landscapes in Shanghai and adjacent regions. Meanwhile, L. formosana trees in some regions were also found to die after being attacked by A. suncei. Conclusion: The phenomenon of A. suncei attacking healthy sweetgum trees is reported for the first within the genus Acanthotomicus. A. suncei is an oligophagous insect, and the host range is limited to the genus Liquidambar. It's unlikely to harm other host plants. A. suncei prefers to American sweetgum, which may be related to the principle of physiological equivalence of the host plant. A. suncei is a serious threat to the introduction and cultivation of north America sweetgum. We recommend that monitoring should be carried out as soon as possible in planting areas of north American sweetgum trees. Once the infestation of A. suncei is found, the infested plants should be removed immediately, and isolation zones should be set up to protect healthy plants, which could prevent the spread of the pest. At the same time, it is necessary to strengthen the research on risk prediction, early warning, prevention and control method in the suitable distribution area of this pest, so as to lay the foundation for the final control of the pest.

Key words: Liquidambar, Acanthotomicus suncei, morphological characteristics, biology, occurrence status