Effect of the western conifer seed bug Leptoglossus occidentalis, an invasive alien insect, on seed production reduction in Japanese black pine Pinus thunbergii

ABSTRACT

To determine the potential reduction of the seed productivity of Japanese black pine (Pinus thunbergii) by the western conifer seed bug (Leptoglossus occidentalis), two feeding experiments were conducted in the center of Kyushu Island, southwestern Japan, in fall of 2020. First, L. occidentalis individuals and a preharvested P. thunbergii cone were enclosed in a nonwoven fabric bag for 2 weeks, which yielded a mean filled seed rate of 18.8% compared with that of 35.6% in the control. Second, L. occidentalis individuals and harvested cones were enclosed in a plastic case for 1 week, affording a mean filled seed rate of 25.7% compared with that of 36.4% in the control. These results suggest that L. occidentalis feeding reduces the filled seed rate of P. thunbergii and damages the seed orchards of this species. Additionally, P. thunbergii seeds from cones damaged by L. occidentalis could be distinguished by their germination ability when sorted using an ethanol floatation technique. Overall, these findings suggest the importance of carefully monitoring L. occidentalis infestation in P. thunbergii seed orchards.

KEYWORDS:

• Pine cone
• pine nut
• filled seed
• seed orchard
• seed sorting

Disclosure statement

No potential conflict of interest was reported by the authors.

Acknowledgements

The authors are grateful to Dr. Takahiro Hosokawa at Kyushu University and Dr. Nobuo Mizutani, Senior Principal Scientist, Institute for Plant Protection, NAROfor their helpful comments on our research, and also Dr. Takashima and Dr. Yasuda at Forest Tree Breeding Centre for use of their soft X-ray system. The authors are also grateful to the staff at Kyushu RBO for managing the experimental materials and supporting the experiments.

Supplementary data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/13416979.2023.2291343