Effect of high temperature shocks on performance of Trichogramma chilonis Ishii (Hymenoptera: Trichogrammatidae)

Key biological characteristics of Trichogramma chilonis Ishii, which govern its performance in the field were studied by exposing pupae and the adults to different temperatures (30 ± 1°C, 33 ± l°C, 36 ± 1°C, 39 ± l°C, 42 ± 1°C and 45 ± 1°C) keeping 80 ± 5 per cent relative humidity daily for six hours. Temperature shocks at ≥ 33 ± l°C resulted in decrease in adult emergence. Fecundity decreased when the parasitoid was exposed at ≥ 30 ± it from day 1 and day 2; at ≥ 33 ± l°C from day 3 and at ≥42 ± J°C on day 4 of pupae formation. Female longevity decreased when the parasitoid was exposed at ≥ 36 ± 1°C from day 1 or day 2 and at ≥ 42 ± l°C from day 3 or day 4 of pupae formation. Temperature shocks of 45 ± 1°C initiated from day 1 of pupae formation proved deleterious to the parasitoid resulting in low adult emergence (24.88%), low fecundity (26.50 egg hosts parasitized/female) and decreased female longevity (8.45 days). When females reared at 27 ± 1°C were exposed to different high temperatures, significant (P = 0,05) decrease in fecundity and female longevity was observed as compared to control. No effect of high temperature exposure on the sex-ratio in the progeny was observed. Results of the present study may help in developing augmentative release strategies of this parasitoid against lepidopterous pests in cotton by devising suitable release techniques.