Bagworms can be very destructive to your trees and shrubs. They are hard to see, but you will notice the destruction they leave behind. If you notice your pines dropping or leaves turning yellow and dying, there is a good chance that these little creatures have made a home in your yard.
What Are Bagworms?
Bagworms are insects that feed on many different species of bushes and trees, but they especially like pines, junipers, Cyprus, cedar, and spruce. The female larvae feed on the tree or bush from spring until August, when they make a bag. They lay 500 to 1,000 eggs, and the female stays in this bag and continues laying eggs.
The males are black and have clear wings, and the females are white without any wings, legs, antennae, or mouths. The female’s sole purpose is to lay eggs. The male travels to the bag in the Fall and mates with the female, and she then lays 500 or more eggs. It is critical to contain the problem before it reaches this stage.
When the larvae are born, they send a silk thread out of the bag and float along it to a host plant. The cycle begins again as these larvae feed until August. You need to address this problem as soon as you can because the number of eggs the females lay can lead to an infestation quickly. They are very destructive and will harm your plants and trees.
How to Recognize Bagworms
Bagworms are often hard to recognize until you have a serious problem. They make bags that are shaped like a spindle out of their silken threads and little bits of trees, and they look like part of the tree or bush.
When the larvae appear in the spring, they start to spin their bags right away, and the bags get bigger as they eat and grow. They hide inside the bags, where the females can produce as many as 1,000 bagworms in a year.
When they mature, the bags will be longer than two inches, and they are no longer able to be killed by pesticides. The bagworm attaches the bag to a branch or somewhere safe where it can hold up for the winter, and the temperatures have to be very cold for them not to survive. They only have one new generation each year, but there can be many bagworms in each generation.
Pick the Bags Off the Trees
If it is early in the season and the bagworms haven’t hatched out of the bags yet, you can pick the bags off the tree and soak it in soapy water. This will kill the worms and eliminate the problem.
The problem is that if there are bagworms up high in pine trees, you may not be able to reach them. This might only work on bushes that are lower to the ground. It is also not possible once the larvae have hatched and made their way out of the bag.
Are There Natural Predators for Bagworms?
If you leave the bags up in the trees, birds will eat the worms. Sparrows are known for feeding on this pest, so you can try to attract them to your property. Sparrows are drawn to areas with food, water, and shelter, so you will need to provide this to attract them. If you can’t or don’t want to use pesticides, this may be your best option.
How to Draw Birds to Your Trees
Besides the fact that birds are pretty and sing beautiful songs, they are helpful because they eat bugs and pests. Sparrows like to have water at ground level, so you can add a birdbath that is low to the ground. They also look for materials they can use to build a nest and thickets or trees where they can live.
They like to have dust baths, so you will want to create that space as well. If you can make a sparrow oasis in your yard, the sparrows will come and help you control your bagworm population.
Use the Bacteria Bacillus Thuringiensis
If you are able to apply this bacteria right as the eggs hatch in the spring, it can effectively control bagworm populations. It doesn’t work as well once the bagworms have gotten bigger. You will buy the bacteria and use a garden sprayer to apply it to the trees. You will need to reapply it every seven to ten days until the bagworms are gone.
Use an Insecticide
If you decide to use an insecticide, you should make sure that you do so right after the bagworms have hatched. If they get too big, this will not be effective. You can buy an insecticide that contains carbaryl, diazinon, or malathion, and apply it to your trees.
Each insecticide will come with instructions from the manufacturer, so you will need to follow them to make sure that you apply it correctly.
Apply Dinotefuran to the Soil at the Base of the Trees
If you apply this chemical to the soil at the base of the tree, it will be consumed by the tree and when the bagworms eat the tree’s foliage, they will die. You need to make this application in early May before the bagworms have hatched, or it will not be effective.
Timeline for Getting Rid of Bagworms
There is a timeline for how to handle bagworms, and it is based on their lifecycle. At certain times during their cycle, certain control measures will be more effective. If you draw birds to your property, they can control the bagworms throughout the entire cycle, but if you want to pick the bags or use insecticides, there are times that you should plan to do so.
Early Spring: In early May, before the bagworms hatch, you can try picking the bags off of your tree. If you have only a few bags and they are in locations where you can reach them, you can effectively control the population this way. Once you pick them out of the tree, you need to soak them in a bucket of soapy hot water. This will kill them.
You can also try releasing the bagworm-eating bacteria at this time. If you apply it as the bagworms are hatching in May, it will target them and eat them.
Another choice is to apply Dinotefuran to the base of your trees in early May. It will be absorbed by the tree, and when the bagworms feed on the foliage, they will die.
June through July: You can use an insecticide during these months. This will be one of the more effective ways of eliminating the bagworm problem because it will kill all of them as long as you do it by the end of July. After this time, the bags become too large to kill with insecticides.
Will Bagworms Come Back?
Even when you get rid of the bagworms for the season, they can come back. When they hatch, they send a silky thread out of the bag, and they follow it to the tree where it anchors. It is not always the same tree where it hatches. This means that you can end up with new bagworms each year from other trees, such as your neighbor’s trees.
Even when bagworms come back, you need to try to eliminate the problem as soon as possible so that they do not have a chance to reproduce and become an infestation. You can use the same methods as above to get rid of these bagworms.
Bagworms are very destructive little pests, and you should get rid of them as soon as you can. The females lay between 50 and 1,000 eggs every year, which can quickly become a huge problem for your yard.
If you can pick them off the trees and bushes, that will work well. Just be sure to soak them in a bucket of soapy warm water. If the bags are too high up in the tree, you will need to find an alternative solution.
Birds, especially sparrows, are natural predators for bagworms, so if you want an organic solution, you should try to attract them to your yard. You can provide a low lying bird bath and a place for shelter, and sparrows may come and take care of this problem for you.
If you need to use an insecticide, you should take care of it as early in the summer as possible. The bagworms grow all summer long, and they can reach a size that is big enough that they are difficult to exterminate. It is ideal to take care of this in May or June, but you can effectively use pesticides in July as well.
Even if you eliminate these pests, have a plan in place for the following spring, as these pests can return. Because each bag contains 500 to 1,000 eggs and they release their thread to exit the bag, you could have them back very easily the following year.