Effect of Light Intensity and Photoperiod on Development, Fecundity and Longevity of Trissolcus grandis (Hym.: Platygastridae), Egg Parasitoid of Sunn Pest, Eurygaster integriceps Puton (Hem.: Scutelleridae)

Abstract Egg parasitoids are the most important natural enemies of Sunn pest, Eurygaster integriceps Puton (Hem.: Scutelleridae), which play important role in the control of this pest. Among its parasitoids, Trissolcus grandis (Thomson) (Hymenoptera: Platygastridae) is the most widely distributed and prevalent species, which used in this research, to determine the effect of light intensity and photoperiod on life history and population growth parameters. At the first part of this study, effect of three light intensities, (5331, 1412.5 and 706 Lux) was studied at 26 ± 1˚C, 50±10% RH and 16:8 (L: D) photoperiod. Significant differences were observed in all stable population growth parameters except net reproductive rate (R0). Total fecundity also showed significant differences among the light intensity treatments. Moreover, effect of four photoperiod regimes, 10:14, darkness, 12:12 and 14:10 h (light: darkness) were studied at constant laboratory conditions. Significant differences were observed among all parameters as they were classified within two groups (10:14 and darkness in a group compared to 12:12 and 14:10 h in the other one). Significant differences were also observed among the treatments of the other parameters including developmental time, total fecundity and sex ratio. Overall, light intensity and photoperiod had limited although significant effects on the most biostatistics of T. grandis. It seems that T. grandis is able to successfully develop, survive and reproduce under a wide range of light regimes.