We investigated the number of airborne pollen of Japanese cypress, Chamaecyparis obtusa Endl., the density of stink bugs, Plautia crossota stali Scott, on the cones of Japanese cypress, and the damage to persimmon fruit by stink bugs in Wakayama Prefecture. In years when the density of overwintering adult bugs was high and the airborne pollen count was low, the peak density of the bug population on Japanese cypress cones was observed as early as July–August and the percentage of damaged persimmon fruit was high. In contrast, the bug population reached peak density in September–October and a low percentage of damaged fruit was observed in years when the density of overwintering adult was low and the airborne pollen count was high. The decrease in bug density on cones, which indicates cone deterioration, was followed by bugs leaving the cypress for persimmon orchards. There was a highly positive relationship between the density of overwintering adults and the number of airborne Japanese cypress pollen, which is closely related to cone production. Thus, the ratio of airborne pollen counts in the current year to that in the previous year (the c/p pollen ratio) is considered an indicator of the stink bug population for the current year. A highly positive relationship was found between the c/p pollen ratio and the time when the percentage of damaged fruit increased, suggesting that the c/p pollen ratio is very useful for forecasting the damage rate of persimmon fruit.
