Effect of synthetic aggregation pheromone of Riptortus clavatus on density and parasitism of egg parasitoid Ooencyrtus nezarae Ishii (Hymenoptera: Encyrtidae) in soybean [Glycine max] fields

(E)-2-Hexenyl (Z)-3-hexenoate (E2HZ3H), a component of a synthetic aggregation pheromone (pheromone) of the bean bug, Riptortus clavatus, attracts females of the bug's main natural enemy, the egg parasitoid Ooencyrtus nezarae. The effect of E2HZ3H on the density of O. nezarae, and its parasitism of R. clavatus, was studied in soybean fields. When fields were treated with E2HZ3H, O. nezarae tended to migrate into them before they were invaded by R. clavatus. O. nezarae also reached higher densities in treated than in untreated fields. In addition, E2HZ3H did not increase the density of R. clavatus. On the other hand, both R. clavatus and O. nezarae migrated into pheromone-treated fields earlier than usual and reached higher densities than in untreated fields. However, E2HZ3H did not increase the percentage parasitism of R. clavatus eggs placed artificially on soybean plants. Eggs close to E2HZ3H or the pheromone were not parasitized to any greater extent by O. nezarae than more-distant eggs.