2.1.2. The Preference of B. tabaci MEDs Assessed by Y-Tube Olfactometer Behavioral Experiments

The preference of B. tabaci MED adults (non-viruliferous and viruliferous) for three plants at a specific time was evaluated by a Y-tube olfactometer. One branch of the Y-tube was placed with the plant, and the other was treated with air as a control. The equipment was ventilated for 30 min to stabilize the air volume at 0.6 L/min. The lighting conditions of the Y-tube were the same during all tests. The central tube is 40 cm, the two branch arms are 30 cm, and the angle between the two arms is 60°. Each B. tabaci MED was put into the main arm after 2 h of starvation. The observation time for each B. tabaci MED was 3 min, and the choice of each plant in any branch was observed when the tested B. tabaci MEDs moved more than 1/3 into one of the two arms. Otherwise, it was regarded as no choice [33]. Each adult was selected only once. A total of 10 whiteflies were used, 10 times in each group, and six groups were repeated. The Y-tube was washed with 95% ethanol after the test. After each test, the positions of the treatment and control were changed to eliminate the influence of the two side arms of the Y-tube. The numbers of B. tabaci were counted in two side arms, and the repellent rate was calculated by the following formula [34]:

Regarding d-limonene, the preference of B. tabaci MED adults (non-viruliferous and viruliferous) was also found by Y-tube olfactometer experiments. One branch of the Y-tube was placed with d-limonene (the concentrations ranged from 10⁻¹ to 10⁻⁶ g/mL, diluted with n-hexane). The configured 2 mL compound was transferred to the filter paper and volatilized in the test tube. N-hexane was selected as the control when evaluating B. tabaci’s selectivity to d-limonene. D-limonene and n-hexane were purchased from Macklin reagent Co., Ltd. (Shanghai, China). The remaining experimental methods were conducted following the procedures outlined in Section 2.1.2.