Differential parasitism performance and host adaptability of key biocontrol Eretmocerus species against two major whitefly pests

Whiteflies are major agricultural pests, and their sustainable management depends on effective biological control strategies. This study investigates the preference, the host performance and the host feeding behavior of two key parasitoid species, Eretmocerus corni and Eretmocerus hayati, against Bemisia tabaci and Trialeurodes vaporariorum. To assess host selection, parasitism, host-feeding, emergence rates, developmental times, proportion of female offspring, and total mortality rate across different host species and instars, both no-choice and choice experiments were conducted. Key findings include: (1) E. corni successfully parasitized all instars of both whitefly species, while E. hayati completed its development only in B. tabaci. Both parasitoids achieved the highest parasitism rates and emergence rates on the second and third instars of their respective hosts. (2) E. hayati exhibited superior host-feeding, faster development, and higher total mortality rate compared to E. corni, additionally, both host-feeding rates and developmental time significantly decreased as the host instar increased. (3) Although E. hayati could not complete its development in T. vaporariorum, it caused substantial mortality through aborted parasitism and superior host-feeding. (4) In the choice tests, E. corni showed a significant preference for T. vaporariorum when both whitefly species were at the same instar stage, whereas E. hayati exhibited no notable host preference. (5) Under the mixed-host condition, both E. corni and E. hayati exhibited increased mortality rates against whiteflies at the same instar compared to the single-host condition. These findings offer valuable insights into the host preference, performance of these parasitoids and provide theoretical guidance for optimizing whitefly biological control.