Influence of nitrogen level and tomato cultivars on the efficiency of Trichogramma principium (Hymenoptera: Trichogrammatidae) on the eggs of Helicoverpa armigera (Lepidoptera: Noctuidae)

Abstract

The efficiency of natural enemies as the key factor in the success of biological control programs, depends on different elements including the quality of their herbivore hosts. Similarly, it may be influenced by nutritional status and genetic differences of host plants in turn. This study was undertaken to determine the parasitism efficiency of Trichogramma principium (Sugonjaev & Sorokina) on the eggs of Helicoverpa armigera (Hübner) reared on different nitrogen fertilized tomato plant cultivars. All experiments were established in a growth chamber under 25 ± 1°C temperature, 60 ± 5% RH, 16:8 h. (L:D) conditions. Treatments included six tomato cultivars (Kingston, Riogrand, Earlyurbana, Redston, Superstrain-B and Primoearly) with four N levels (0, 2.1, 3.0, 3.9 g/ pot, Nitrogen as Urea 46%), in 5 replications. The value of the net parasitism rate (C0) of T. principium varied from 13.42±1.00 to 23.39± 2.59 hosts on the eggs of H. armigera reared on En0, and SBn+, respectively. The transformation rate from host population to parasitoid offspring (Qp) on all treatments was close to 1 (C0 ≅ R0). The finite parasitism rate (ω) which is used to determine the efficiency of a parasitoid, estimated as 0.1525 (min.) and 0.3164 (max.) hosts parasitoid-1 day-1 on the hosts reared on Earlyurbana and Superstrain-B, respectively. In general, T. principium had higher parasitism capacity on the hosts reared on Superstrain-B, Kingston and Riogrand with highest N levels, which were more suitable for parasitoid. This study showed that parasitism capacity of parasitoid was influenced by the host plant cultivar as well as positively correlated with the host plant nitrogen contenets.

Keywords

• biological control
• parasitism capacity
• nitrogen fertilization
• tri-trophic interactions