Orius similis prefers to prey on the young larvae of Encarsia formosa parasitizing on Bemisia tabaci

Abstract

Orius similis and Encarsia formosa are important natural enemies of Bemisia tabaci. However, there is limited understanding regarding the impact of O. similis on the control of B. tabaci by E. formosa when they are used in combination. Temperature changes will affect the food web, and Intraguild predation (IGP) is a fundamental component that constitutes a complex food web. Therefore, studying the effect of temperature on IGP is of great significance for understanding the mechanism of species interaction and improving the biocontrol ability of natural enemies. Our study investigated the interference of female adults of O. similis on unparasitized and parasitized B. tabaci nymphs (including 1-, 4-, 7-, and 10-day-old parasitoid immature nymphs) at different temperatures (19, 22, 25, 28, and 31 °C). The results showed that only the parasitism rate of E. formosa was lower than that of the treatment without O. similis on 1, 4, 7 and 10 days after being parasitized by E. formosa, indicating that O. similis preyed on E. formosa. In both the no-choice and choice experiments, O. similis showed a preference for feeding on B. tabaci nymphs that had been parasitized 1 and 4 days earlier, across various temperature conditions. When both unparasitized B. tabaci nymphs and parasitized 10-day-old B. tabaci nymphs were present, O. similis preferred to prey on unparasitized prey. Our results provide evidence that IGP interactions may be greatly affected by future increases in temperature. When the temperature increased from 19 to 28 °C, the IGP of O. similis was promoted with the increase in temperature. When the temperature exceeded 28 °C, IGP was inhibited. Therefore, in the combined application of these two natural enemies, the O. similis can be released again in the period or time period when the temperature is stable at 22–25 °C after 10 days of release of E. formosa to reduce the IGP intensity, so as to achieve better control effect and accelerate the establishment of an efficient biocontrol system of natural enemies of B. tabaci.