Stem borer (Undetermined) in Lactuca

In February 2026, in the upper part of a dead stem I observed sparse grains of whitish frass scattered here and there on the surface of the pithy inner lining of the hollow stem interior. The trail of frass grains led down to a cynipid gall about 65-70 cm above ground level, and I did not follow it into the gall or below this point. The color, size, and shape of the grains were most similar to erotylid or mordellid frass from other hosts, but I could not rule out some other kind of coleopteran or lepidopteran borer as the resemblance was inconclusive and I did not observe the larva directly.