Effects of continuous multi-generational rearing with an alternative host on the adaptability of Encarsia formosa

This study aimed to evaluate the adaptability of Encarsia formosa reared on the alternative host Bemisia tabaci Gennadius to two whitefly species. E. formosa was transferred from its original host, Trialeurodes vaporariorum Westwood, to the alternative host, B. tabaci, and continuously reared on B. tabaci nymphs for 15 generations.

We used E. formosa from T. vaporariorum as a control group (G₀) and analysed changes in biological parameters, such as the number of whitefly nymphs parasitized, number of hosts fed upon, developmental duration and emergence rate of E. formosa after successive generations (G₁, G₅, G₁₀ and G₁₅) of continuous rearing on B. tabaci.

The results showed that both the number of whitefly nymphs parasitized and total host mortality caused by E. formosa on B. tabaci nymphs and T. vaporariorum nymphs were significantly lower in G₁ and G₅ compared to G₁₀ and G₁₅. The developmental duration for G₁, G₅ and G₁₀ of E. formosa was significantly shorter on B. tabaci than on T. vaporariorum. No significant differences in the number of host feeding were observed either across generations or between the two whitefly species. Overall, the adaptability of E. formosa reared on alternative hosts to two whitefly species increased significantly with increasing generations. After rearing up to the 10^th generation, the adaptability of E. formosa to B. tabaci was significantly better than that of wasps reared on T. vaporariorum. However, their adaptability to T. vaporariorum showed no significant difference compared to E. Formosa reared from T. vaporariorum.

The findings of this study provided a theoretical foundation for guiding the rearing and effective use of parasitoid wasps.