By Paul Schnare

Saturday, May 31, 2003


Bagworms are insect pests that can defoliate and kill evergreen trees and shrubs.  In the Heartland, bagworm eggs hatch around the 15th of May.  The resulting larvae exit the bag and begin feeding on the foliage of the tree or shrub that they are on.  Initially the bagworm is about 1/16 inch long, and looks like a small cone.  As the larvae feed, they increase in size and start forming a bag around themselves. 


The larvae continue feeding until August.  At that time, metamorphosis occurs, and the resulting male moths fly to female moths located in the bags of the old larvae.  Fertilization takes place and the female lays eggs in the bags and dies.  The eggs overwinter in the bags and the process begins again the following spring. 


Feeding bagworm larvae can kill evergreen trees and shrubs if completely defoliated.  Larvae must be killed as early as possible after hatching in order to prevent damage.  Each bag will produce on the average of 750 bagworms. 


Control early in the season can be obtained with the use of sevin, methoxychlor, diazanon, cygon, or Bt.  As the worms get larger, later in the season, they are harder to kill.  At that time you only get good kill with methoxychlor, diazanon, or cygon.