Bag worm treatment
I have numerous Leyland Cyprus trees and a Blue Spruce, that seem to have been infected with bag worms. What do you suggest to help get rid of this issue and remove the worms from the trees? Also is there any specific type of fertilizer you would recommend to help the trees, when/if I get rid of the worms?
Montgomery County Virginia
Bagworms can be a serious problem on many of our ornamental trees and shrubs. If you have a light infestation on smaller plants, hand picking the bags and destroying them (picking them off and burning them if allowed in your area) is a good way to gain control of the problem. Otherwise, spraying with an approved insecticide during early to mid-June is effective. If you wait later in the summer they are much harder to kill, and any earlier it is unlikely you will get good coverage on the unhatched caterpillars. This publication from Virginia Tech gives a lot of information on this pest.
Chemicals that are approved for use in Virginia for bagworms include carbaryl (Sevin), Bt (Bacillus thuringiensis), Malathion, Neem oil, Permethrin, as well as several others. A full service garden center should be able to direct you to the proper treatment. Just be sure it is labeled for use on the specific trees you plan to treat and read and follow the label directions. These need to be sprayed to cover the tree lightly to get good contact.
If the trees are very large, spraying can be difficult for a homeowner and we suggest you contact a certified arborist for the treatment. The Montgomery County office of Virginia Cooperative Extension may have a list of arborists that work in your area. You can get their contact information on this website.
If you have additional questions on this subject, please use the reply feature within this email or contact your local Extension office. Thanks for using Ask an Expert!
Also, most trees and shrubs do not require additional fertilizer. If you're concerned that the soil may be very poor in their area, a soil test will help you decide if it is a good idea and will give you recommendations for specific fertilizers to use. You can access Virginia Tech's soil testing laboratory at this website for additional information.