Four-FPA inhibits root growth and reduces the survival rate of WBPH nymphs. (A and B) Mean survival rate (+SE, n = 8) of 15 newly hatched WBPH nymphs fed on plants that had been grown in nutrient solution with 0 to 5 mg L−1 4-FPA for 12 h (A); or that had been sprayed with 4 mL of 0 to 100 mg L−1 4-FPA for 12 h (B); 1 to 8 d after exposure. (C) Growth phenotypes of plants grown in nutrient solution containing 0 to 5 mg L−1 4-FPA for 10 d. (D and E) Mean root mass (+SE, n = 15) (D); and root length (+SE, n = 15) (E) of plants grown in nutrient solution containing 0 to 5 mg L−1 4-FPA for 10 d. Asterisks indicate significant differences between treatments and controls (*P < 0.05, **P < 0.01, Duncan’s multiple range test). Upper indicates treatment methods of 4-FPA and its structure.