4.4. Plant Treatments

For bimerthiazol treatment, two methods were used: root treatment and spray treatment. For root treatment, plants were grown in nutrient solution, and bimerthiazol (first dissolved in N,N-dimethylformamide, 1 mg per mL of N,N-dimethylformamide)—at final concentrations ranging from 10 to 50 mg L⁻¹—was added (with 0.01% Tween-60). Control plants (Con) were grown in nutrient solution without bismerthiazol but with an equal volume of N,N-dimethylformamide and Tween-60. For spray treatment, bismerthiazol was first dissolved in N,N-dimethylformamide (1 mg per mL of N,N-dimethylformamide) and then diluted in distilled water (with 0.01% Tween-60) at concentrations ranging from 50 to 100 mg L⁻¹. The above-ground parts of each plant were sprayed using an atomizer with 2 mL of bismerthiazol solution twice at interval of 4 h. Control plants were sprayed with distilled water containing the same volume of N,N-dimethylformamide and Tween-60. For WBPH treatment, individual plants were infested with 15 WBPH nymphs or gravid females that were confined within a glass cylinder (diameter 4 cm, height 8 cm, with 48 small holes, diameter 0.8 mm), and the top of the cylinder was covered with a piece of sponge. Empty cylinders were attached to control plants (non-infested plants).