2.2 BPH Bioassays
The choice test was conducted as follows (Li et al., 2023): two rice plants were potted side-by-side in the same plastic container, and each plant was placed in glass cylinders (2 cm diameter × 8 cm height), which surrounded the basal stem of each plant. One was infested with 20 gravid BPH female adults, and the other was used as an un-infected control. After 24 hours of infestation, BPHs were removed and one pair of plants was confined in a glass cylinder (4 cm diameter × 8 cm height) into which 15 fifth-instar nymphs or gravid BPH female adults were released in the middle of the two plants. Afterwards, BPHs settling on each plant were counted at 2, 4, 8, 12, 24, and 48 hours, respectively. The experiment was repeated 12 times with 15 insects per replicate.
In the survival rate and honeydew measurement tests, the gravid BPH females pre-infested and control plants were prepared using the same method as above. Third-instar BPH nymphs were allowed to feed on rice plants, stems of rice plants (one plant per pot) were confined individually within glass cylinders, into which 15 third-instar BPH nymphs were released (Ji et al., 2017). The number of surviving BPH nymphs in each cylinder was recorded every day. The experiment was repeated four times. The honeydew was measured as follows (Ji et al., 2021): a brachypterous newly emerged BPH female adult was placed into a small Parafilm bag (6×5 cm), which was then fixed on the stem of a rice plant. The amount of honeydew excreted by a female adult was weighed (to an accuracy of 0.1 mg) at 24 hours after the start of the experiment. The experiment was replicated 18 times.