Nymphs insert their needle-like mouthparts into lower surfaces of the leaf and inject their saliva [which] causes a shallow depression [to form] on the lower leaf surface. Then a deep purple spot develops on both leaf surfaces. However, the top surface of the feeding site may have a green spot in the middle of the purple splotch. The veins may also turn purple over much of the lower leaf surface.

- Baker, James: (2019) Rudbeckia Triozid: PDIC Factsheets^©