The effect of temperature on the bionomics of Trichogramma euproctidis (Hym.: Trichogrammatidae) parasitizing the tomato fruitworm, Helicoverpa armigera (Lep.: Noctuidae)

In this study, the life history characteristics of Trichogramma euproctidis (Girault), an established egg parasitoid species in southwestern Iran, parasitizing Helicoverpa armigera (Hubner) were examined at 18, 21, 24, 27, 30, and 33 °C. The results showed that different constant temperatures significantly affected the number of parasitized eggs, development time, sex ratio, tibial length, number of parasitoids per host egg, progeny longevity, and fecundity. T. euproctidis failed to complete development at 18 °C, the lowest temperature tested. The mean developmental duration from egg to adult female decreased from 15.33 days at 21 °C to 7.25 days at 33 °C. An average of 188-degree days was required to complete development above the lower threshold temperature (7.2 °C). Survivorship was 96.20, 97.20, 98.33, 85.46, and 82.22 % at 21, 24, 27, 30, and 33 °C, respectively. The mean longevity of T. euproctidis ranged from 11.60 days at 21 °C to 4.57 days at 33 °C. Mean total progeny ranged from 19.50 / female at 33 °C to 168.70 / female at 21 °C. Data analysis demonstrated that different constant temperatures had a significant effect on the net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and generation time (T). The intrinsic rate of increase (r) improved with temperature from 0.240/day at 21°C to 0.370/day at 27 °C and then decreased at higher temperatures. Generation time decreased from 16.90 days to 7.53 days with increasing temperature. The optimal temperature for development and reproduction of T. euproctidis was 27 °C. The results of this study showed that this strain of T. euproctidis appears to have the potential to be utilized in integrated management programs targeting H. armigera.