I have a very large (12 Ft.) arborvitae infested with bagworms. Have removed all I could find -- about 50. Should I spray it? With what? Should I also take preventive measures next spring, or when? Thank you.
Great job on beginning the removal process of the bags from your arborvitae! Because of the time of year, your best bet is to continue manually removing the bags that you find on your tree. This is because the insecticides available to remove the insects are not effective when applied to the bags. However, early June, once the insects have hatched, is the best time to apply an insecticide for a more comprehensive control. The article Bagworms on Landscape Plants provides some great information about the life cycle of bagworms as well as a table of recommended insecticides. Please remember to always read and follow application and safety instructions when using chemicals. If you need additional help or have any other questions, please contact the Jefferson County Extension Service at 502-569-2344.