Fig. (1) Radial diffusion growth inhibition assay. Tryptic soy agar plate contained about 4 x 10⁶E. coli. Six μl of sample was applied to the wells. The plate was incubated at RT to allow the sample to diffuse radially into the agar, and then incubated at 37°C overnight. Bacterial growth inhibition was indicated by clear area surrounding the well. A: spruce budworm (artificial diet) gut juice, B: balsam foliage water extract, C: spruce budworm (foliage diet) gut juice, D: balsam foliage water extract boiled for 30 min, E: spruce budworm (foliage diet) frass water extract, F: spruce budworm (artificial diet) hemolymph, G: spruce budworm (foliage diet) hemolymph.