The efficiency of biological control agents can be influenced by several factors such as the quality of their herbivore hosts and nutritional status of host plants. This study focused on parasitism capacity of Habrobracon hebetor(say) on Helicoverpa armigera (Hübner) reared on different nitrogen fertilized tomato plant cultivars. All experiments were carried out in a growth chamber at 25 ± 1 °C, 60 ± 5 % RH and 16:8 h L:D. Six cultivars including Kingston (K), Riogrand (RG), Earlyurbana (E), Redston (R), Superstrain-B (SB) and Primoearly (P), with four nitrogen levels (0, 210, 300, 390 kg Ha-1 N as Urea 46 %), were evaluated in 5 replications. Parasitism data were analyzed using CONSUME-MSChart software. The means, variances, and standard errors of the parameters were estimated with C0 bootstrap method. The value of the net parasitism rate ( ) of H. hebetor varied from 9.50±1.33 to 12.34±2.31 host/parasitoid on H. armigera reared on Primoearly with the lowest and Kingston with the highest N, respectively. The transformation rate from host population to parasitoid offspring ( Q p ) on all treatments was close to 1 (C0≅R0). The total parasitism capacity of a stable population ( ) ranged from 0.224±0.094 to 0.358±0.090 host/parasitoid on H. armigera reared on Primoearly with the lowest N and Kingston with the highest N, respectively. The lowest observed values of the finite parasitism rate ( ) included 0.302, 0.263, 0.266, 0.285, 0.281 and 0.261 hosts parasitoid-1 day-1 on hosts reared on K, RG, E, R, SB and P at the lowest N level, respectively; however, the highest recorded values for finite parasitism rate ( ) were 0.431, 0.332, 0.281, 0.303, 0.390 and 0.329 hosts parasitoid-1 day-1 observed on the same cultivars at the highest N level, respectively. In general, based on biological attributes obtained in the current study, H. hebetor revealed the optimum fitness on hosts reared on Kingston with the highest N level. It is concluded that parasitism capacity of t
