The cocoons resemble cones and are hard to spot, but severe infestations can kill trees. The insects are drawn in particular to cedars, junipers, Leyland cypresses, pines and arborvitaes. Use a glove and drop bags in a bleach solution. Bagworms in upper branches can be sprayed with an insecticide labeled for this pest, although the cocoons make pesticides less effective at this stage.