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Abstract
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Trichogramma principium (Sugonjaev & Sorokina) is an effective natural enemy in the agricultural ecosystems of Iran. Nevertheless, its biological characters have not been investigated in detail. A study was conducted to evaluate the wasp life table parameters on Helicoverpa armigera (Hübner) fed by six different cultivars including Kingston, Riogrand, Earlyurbana, Redston, Superstrain-B and Primoearly, with four N levels (0, 210, 300, 390 kg/h N as Urea 46 %) under controlled conditions (25 ± 1 °C, 60 ± 5 % RH and a photoperiod of 16:8 h L:D). Treatments were replicated 5 times. Observations were noted down on the mortality and developmental time of immature stages as well as the longevity and fecundity of adult parasitoid. Data analysis was carried out based on age-stage two sex life table method. Results indicated that the mean pre-adult duration (from egg to adult emergence) was 11.59±0.12 and 10.41±0.08 days on H. armigera reared on Primoearly and Superstrain-B, respectively. The total pre-oviposition period ranged from 10.52±0.11 to 11.65±0.20 days on Superstrain-B with standard N concentration and Primoearly with the lowest N concentration. Similarly, the longest and the shortest adult longevity for females were observed on Superstrain-B with the highest N level (3.51±0.14 days) and Redston with R0 the lowest N level (2.07±0.15 days), respectively. Additionally, the net reproductive rate ( ) was estimated as 13.42±1.0 to 23.39±2.59 offspring on different treatments. The intrinsic rate r of increase ( ) and the finite rate of increase ( ) varied from 0.0905 day-1 and 1.0914 day-1 on Earlyurbana plus zero N level to 0.2142 day-1 and 1.2390 day-1 on Superstrain-B plus highest N level. The mean generation time ( ) of T. principium ranged from 12.58±0.11 to 13.65 ±0.17 days on different treatments. With regard to demography of T. principium, the host plant could be an effective factor on life history characteristics of the parasitoid. On the other hand, suitabili
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