Fig. 1.

Feeding assays of P. versicolora larvae with leaves from beetle-damaged sick willows (SW) and healthy willows (HW). A Representative bioassay with detached sick leaves (SL) and healthy leaves (HL) from two sampling sites. Leaves were fed to first-instar P. versicolora larvae and replaced with fresh young leaves daily. The photographs were taken on day 3. Red arrows: the leaf sites damaged by beetle. B Leaf area consumed by first-instar P. versicolora larvae in A. C, D Pupation rate (C) and eclosion rate (D) of P. versicolora feeding with SL and HL from two sampling sites. E Larval weight after the indicated number of days of feeding on SL and HL from two sampling sites. S1, field site 1; S2, field site 2. HL-^HW: healthy leaves of healthy willows; HL-^SW: healthy leaves of sick willows; SL: sick leaves of sick willows. Significant differences between two groups were determined by Student’s t-test. *P < 0.05, **P < 0.01, ***P < 0.001