Life table parameters and parasitism rate of Trichogramma embryophagum in long–term mass rearing on Ephestia kuehniella eggs

The quality of biological control agents has a main role in the success of a biological control program. It is believed that long–term mass rearing in confinement may affect the quality of them. In this study, the life table and parasitism parameters of Trichogramma embryophagum (Hartig) reared on Ephestia kuehniella Zeller eggs was studied for 32 generations (G). The initial population of wasp from the pomegranate orchards of Kuhdasht County (Lorestan Province) and the population of host from an insectary, from Hamadan (Hamadan Province), were prepared and reared at 26°C, RH of 65%. Data on the duration of different developmental stages, survival, fecundity and parasitism in G5, G10, G15, G20, G25, G28, G30 and G32 were determined separately, and were analyzed using age–stage, two–sex life table theory with use of TWOSEX–MSChart and CONSUME–MSChart programs. The adult longevity was not significantly different until the 15th generation, but declined as the generation numbers increased and reached 7.15 days in G30. The highest and lowest fecundities were observed in G5 (72.73 eggs) and G32 (28.64 eggs), respectively. The highest values of net reproductive rate (R0) were seen in G5 to G15. The values of intrinsic rate of increase (r) in G5 to G15 were significantly higher than the other generations. The r value from 0.301 day–1 in G1 reached to 0.229 day–1 in G32. Also the finite rate of parasitism (ω) with increasing the generation numbers declined and from 0.478 host/parasitoid/day in G5 reached to 0.332 host/parasitoid/day in G32. According to the findings of this study, due to the constant rearing conditions and not adding wild individuals with genetic diversity to the population, after the 15th generation, the quality of reared individual’s decreases significantly.