Stem borer (Undetermined) in Berteroa

I observed a stem of the host that contained two affected areas. In each affected area, a limited amount of tunneling was present in a localized region of the pith adjacent to a node. The tunneling connected directly to a round hole in the leaf scar where the petiole of the stem leaf had formerly been attached. I hypothesized that the insect had begun its activity in the petiole of the stem leaf, then tunneled into the stem from there, where it had evidently completed this part of its development and then exited the plant.

Culprits were absent by the time I noted the damage in early September.