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

Abstract

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.