The following is information on bagworms in the fall. They are now inside the bags and the only control is hand picking or waiting until they come out next year.
Obviously any type of spray applied in the fall or winter for bagworm control would be a waste of time and material. Over-wintering eggs are contained within the dead female bags. Most of the bags containing eggs are located on the upper portions of infested trees or shrubs. With this higher elevation, it is theorized that a certain percentage of a recently hatched population in late spring can more effectively be transported by the wind to new hosts. Remove individual bags by hand when populations are low and the upper portions of the plant can be reached. Otherwise, indicate in your records that sprays may be required during the late spring or early summer when the young larvae hatch and begin feeding.
Bagworms on conifers have pupated. During the fall mating and egg lying will occur within the female sack. Bagworms hatch out in mid-June from the over-wintering eggs within the dead female bag. Researchers in Kentucky have determined that most newly hatched bagworms disperse away from the ‘parental’ host plant. This may be because the offspring from only a few bags have the potential to defoliate a small plant. About 75% of immature bagworms disperse by ‘ballooning’ into the wind, and were observed traveling hundreds of feet. Failure to control populations upwind from a susceptible host may leave a potential reservoir of the pest in the future. (Reference: Cox and Potter, J. Arbor. 9/90) .
Information from Steven K. Rettke, Ornamental IPM Program Associate in the September 17, 2009 edtion of the Plant & Pest Advisory, Landscape, Nursery & Turf Edition, from Rutgers University http://njaes.rutgers.edu/pubs/plantandpestadvisory/2009/ln091709.pdf