Behavioral change of Riptortus pedestris (Fabricius) female during reproductive diapause

Riptortus pedestris (Fabricius) (Hemiptera: Alydidae) is an important pest of soybean in Korea and Japan. It enters reproductive diapauses by short day length (less than 13.5 h) in September in Korea. Since we observed higher population level of R. pedestris during late summer to fall period in soybean fields where pheromone traps were installed, we suggest a hypothesis that R. pedestris is more responsive to aggregation pheromone during reproductive diapause. The hypothesis was tested by examining response of female R. pedestris either collected seasonally from fields or reared in short day length (10:14 L:D) in laboratory to aggregation pheromone by Y-tube olfactometer tests. We also assessed willingness of mating of both the field and laboratory population. Riptortus pedestris collected in September (74%) showed higher response to the aggregation pheromone than those collected in July (40%). In laboratory population of female R. pedestris in reproductive diapause (62%) also showed higher response to the aggregation pheromone than those not in diapause (46%). Both sexes of R. pedestris in reproductive diapause mated less frequently than those not in diapause. This is the first observation of higher response to aggregation pheromone by conspecifics in reproductive diapause.

 

Key Words: Riptortus pedestris, photoperiod, reproductive diapauses, aggregation pheromone