A study of the effect of constant temperature on some biological parameters of the parasitoid, Diadegma semiclausum Hellen (Hymenoptera:Ichneumonidae) in laboratory conditions

Abstract

The parasitoid Diadegma semiclausum Hellen (Hymenoptera:Ichneumonidae) has been studied in the Biological Control Studies and Research Center (BCSRC) under controlled laboratory conditions at three levels of temperature 22, 26 and 30±1 C°, 60±5% R.H. and a photoperiod of 16:8 (L:D) h . Sampels were collected during the period from April to July 2019 in Abu Jarash region in (Damascus–Syria). The parasitoid was reared on Diamondback moth, Plutella xylostella which is reared on cabbage plants, Brassica oleracea var capitata. Results showed that the longest developmental period from egg to pupa was on 22°C with average 7.39±0.33 days, and the lowest developmental period was on 30°Cwith average 4. 66±0.18 days. The longest developmental period from pupa to adult was on 22°C with average 9.39±0.32 days, and the lowest period was on 30°C with average 6.38±0.17 days. The longest developmental period from egg to adult was on 22°C with average 16.78±0.08 days, and the lowest period was on 30°C with average11.04±0.26 days. The lower developmental threshold (LDT) from egg to pupa was 7.9 °C, 5.33°C from pupa to adult, and 6.5°C from egg to adult. D. semiclausum required a Sum of Effective Temperatures (SET) of 250 degree-days above the lower developmental threshold 6.5°C to complete development from egg to adult.