Goldenrod Gall Fly larvae live inside the stems of goldenrod. The fly larvae manipulate goldenrod into creating spherical feeding sites for the fly larva. Larvae are protected against the wind and rain, and manipulate the plant into providing a continuous source of nutrition.
In summer, larvae are in a state of growth and development. They cannot withstand temperatures below freezing. In autumn, the larvae are fully developed and the plants senesce. About this time of year,…
Source: Living With Insects Blog