Tetramesa romana may sometimes cause no visible gall. However, galls are [sometimes] visible as swollen protuberances on side shoots ...
Gall tissue was found at the shoot apical meristem ... or within 3 cm below ... Young gall tissue was white, while older material ... was yellow. Gall tissue filled the stem cavity, causing exterior shoot distension within 2 weeks of oviposition. However, on main shoots greater than ca. 1 cm in diameter, gall formation often occurred with no visible shoot distension.
”- Moran, Patrick J. and John A. Goolsby: (2009) Biology of the galling wasp Tetramesa romana, a biological control agent of giant reed©