Tips for Getting Rid of Bagworms

Bagworms, also called case moths are the scourge of evergreens but they can also attack deciduous trees.  The bagworm encases builds a protective, camouflaged coating made from the leaves of the tree and lays its eggs inside a sac which closely resembles a pine cone. This makes bagworms difficult to identify and also to kill. To stop your trees from being killed by the bagworm, you will need to learn more about them and their lifecycle.



Bagworms are found in New England, as far down as Texas but are mostly concentrated in the Midwest. The caterpillars feed for about six weeks, the bag becomes larger as they grow and the will withdraw into it if they are disturbed. As they mature the larvae strip evergreens of their needles and consume entire leaves of deciduous trees leaving only the larger veins, effectively defoliating the plants. This can ultimately result in the death of the tree.

 When they are tiny, caterpillars can spin strands of silk which can be carried by wind, ready to infest another tree. When they are bigger they simply crawl to their next victim.

 To prevent serious damage when numerous small bagworms are present, an insecticide such as Bacillus thuringiensis, an organic control for caterpillars may be used. This will be usually in early spring while the caterpillar are very small. Whilst there are numerous chemical sprays available for the control of bagworms, Bacillus thuringiensis (or Bt) is a bacteria and is safe to use around children and pets.

 If the bagworms have gone unnoticed, the bags will increase in size until the autumn when they will resemble pine cones, at this stage and if only a few small trees or shrubs are infested, the bags can be removed by hand and burnt. Each one will contain around 300 eggs ready to hatch and cause more devastation next spring, so to be effective this must be done during autumn, winter or early spring before the eggs are able to hatch. It is ineffective to spray with insecticide at this stage.

 Even if you have removed the bags, new bagworms can spread to your trees from outside sources, so you will still need to spray. The insecticide Bt consists of live bacteria which are harmless to pets, humans, and plants, but lethal to bagworms. You can also use this treatment without worrying about harming beneficial insects such as bees, it is safe for them.  Bt is therefore ideal for spraying regularly to control bagworms while they are active. It can be purchased at garden centers or nurseries as Dipel or Thuricide. Always read and follow the instructions exactly.

Some people will mention burning as an effective method of getting rid of bagworms. However, these means are not recommended by most professionals. It is a risky theory for means of controlling a pest problem because of the risk of damaging the tree or even destroying the entire tree by fire. Cutting the branches seems like the better approach. However, take caution as an unexperienced person can cause more damage than the bagworms.