Pesky Bag Worms and How to Kill Them

Bag worms are a real threat to coniferous trees and can be difficult to kill. However, it’s a “kill or have your trees killed” proposition, so it is important to be aggressive and thorough in your battle with bag worms, also called bagworms.

Spotting Bag Worms
These moth larvae produce small bags that house dozens of individuals. The problem is that the bags look very similar to pine cones, outstanding camouflage for hiding in your Douglas Fir or White Pine.
If bag worms are known to be lurking in your neighborhood, scan your trees for them on a regular basis. A pair of binoculars can be very helpful in examining the trees from the ground. Start at the top of the tree and work your way down and from side to side.
Look for the small gray-brown bags they create or for brown needles or branches, another sure sign of damage to your evergreen.

How to Get Rid of Bag Worms
Bagworms are not easy to get rid of. You’ve basically got two options: Remove them manually or use pesticides to kill them.

Spraying Bag Worms with Pesticide in the Spring
In spring and very early summer, when the bag worms are forming their tents, they can be effectively destroyed by spraying them with pesticide. The best products for getting rid of bagworms contain either acephate or permethrin. These sprays should be available at your local home and garden stores or home improvement stores.

Use the spray directly on the larvae or caterpillars. Be thorough but you don’t have to overdo it. A little goes a long way. Spray may also be used if the caterpillars are hatching out of the bags. In fact, if you catch them at this point in their lifecycle, spray pesticide is your only good option for stopping their spread and the damage they can do.

For large-scale infestations, you may need to call in a pest control company to do the job with their commercial sprayers.

Removing Bagworms Manually
If you don’t want to use pesticides, or if you discover bag worms when they are safely ensconced in the bag where spray cannot effectively penetrate, you’ll have to manually remove them from your trees.
If the bag is at the end of a branch, you may simply want to prune off the part of the branch it inhabits. If it is in the middle of a large branch, you may have to physically pull the bag from the tree. This can be difficult and messy.

When using a ladder, always enlist a second pair of hands to help secure the ladder. Your safety is more important than anything else.

Once you’ve removed the bags, either immerse them in water or burn them. Don’t simply throw them into waste bags to be removed to a landfill or composting area. If you do that, hardy bagworms may become someone else’s problem, and who knows, possibly yours again.


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