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

To determine the potential reduction of the seed productivity of Japanese black pine (<i>Pinus thunbergii</i>) by the western conifer seed bug (<i>Leptoglossus occidentalis</i>), two feeding experiments were conducted in the center of Kyushu Island, southwestern Japan, in fall of 2020. First, <i>L. occidentalis</i> individuals and a preharvested <i>P. thunbergii</i> 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, <i>L. occidentalis</i> 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 <i>L. occidentalis</i> feeding reduces the filled seed rate of <i>P. thunbergii</i> and damages the seed orchards of this species. Additionally, <i>P. thunbergii</i> seeds from cones damaged by <i>L. occidentalis</i> could be distinguished by their germination ability when sorted using an ethanol floatation technique. Overall, these findings suggest the importance of carefully monitoring <i>L. occidentali</i>s infestation in <i>P. thunbergii</i> seed orchards.