Stem borer (Lepidoptera: Tortricidae) in Helianthus

I found two stems occupied by this borer in late winter. Each stem housed a single larva in its tunnel in the middle to lower portion of the stem, at least 20 to 30 cm above ground level, with the larva having accomplished the tunneling while the stem was still alive during the previous growing season. One larva that I collected pupated in the stem and emerged as an adult in spring, leaving the pupal exuviae partially exserted through a hole in the wall of the stem.