Effect of a non‐host plant Phaseolus vulgaris on larval performance and oviposition of the oriental tobacco budworm Helicoverpa assulta (Lepidoptera: Noctuidae)

The oriental tobacco budworm, Helicoverpa assulta, is a specialist herbivore feeding on a few plants of the Solanaceae family including tobacco. Larval performance and adult oviposition of H. assulta were investigated in a non-host plant, Phaseolus vulgaris (Fabaceae) in comparison with two solanaceous host plants, Nicotiana tabacum and Datura stramonium. Larvae provided with the P. vulgaris leaf died off at day 15, whereas 50% and 40% of larval populations fed on the leaves of N. tabacum and D. stramonium, respectively, survived at day 15. Larval growth upon feeding showed significant difference between the non-host plant (P. vulgaris) and the host plants (N. tabacum and D. stramonium), but it was not significantly different between the two host plants. In the no-choice experiment of oviposition, gravid females laid more eggs in N. tabacum and D. stramonium than in P. vulgaris. When the most likely acceptable host plant, N. tabacum, and the non-host plant, P. vulgaris, were subjected to the choice experiment of oviposition, H. assulta females preferred to lay eggs in N. tabacum, where eggs were continuously laid during the whole experiment period. However, eggs in P. vulgaris were hardly detected throughout the period. This study showed that the non-host plant, P. vulgaris, had a negative influence on the larval performance and adult oviposition of H. assulta, implying neonate stage is critical for larval survivorship, and ovipositional preference by the female is highly specialized to host plants. Further investigation is required to identify non-host factors, which could be applied to the development of alternative pest management strategy against H. assulta.