Deter pesky bagworms from hanging around in your trees
What happens when your evergreens start looking anything but green? It could mean that you’ve got a bagworm infestation. The good news is bagworms can be effectively removed if you catch them early enough. Whether you’ve just noticed these little pests or you’re in panic mode, find out how to get rid of bagworms and protect against future appearances.
A bagworm, Thyridopteryx ephemeraeformis, is an insect that feeds on trees and shrubs, especially evergreens. Adult male bagworms are small, moth-like, flying insects with a wingspan of roughly 1 inch. Female bagworms look more like a grub and cannot fly. The larvae, pupae, and adult females live inside little bag-shaped homes made from leaves, needles, twigs, and their own silk—hence the name, bagworm.
Females lay their eggs inside the cocoons. You can sometimes spot the small, black moth-like males emerging from the bags after mating with the females—this usually happens in August or late summer.
Bagworms are a native insect to the U.S. and are typically found in the eastern half of the country. They are also common in Kansas and Nebraska. While bagworms are not of great concern in a forested setting, this little defoliant is a pest in the urban landscape with a penchant for evergreens, such as arborvitae, eastern red cedars, cypress, junipers, pines, and spruces. They can also be found in deciduous trees, including apples, elms, oaks, Japanese maples, poplars, and willows, among others.
The most obvious sign of a bagworm infestation is unhealthy leaves and excessive, unseasonable leaf drop on your tree or shrub. When the “bags” or cocoons are small, they are not always as easy to see in a tree but are often more visible in the winter. A heavy infestation shows obvious small brown bags, usually about 2 inches long, dangling from branches throughout the tree.
Now that you’ve identified your garden pest, you want to get rid of them. To eradicate this unruly pest, you can choose from several mechanical and spray-treatment options.
For mild infestations, you can try a couple of effective methods like hand-picking and making your yard more attractive to bagworm predators.
If you spot bagworms early on and the infestation is mild, you can manually pick off the bags. It is important that you destroy and dispose of the bags, as they contain the eggs—not disposing of them properly can result in reinfestation. Once you’ve picked the bags, put them in a bucket with hot, soapy water to kill off any grubs or eggs inside. Immediately throw away remnants in a sealed bag and do not leave them in your yard or compost.
Be sure to check all of your trees and shrubs in late fall, winter, or early spring before the tree begins to leaf out again and the new eggs hatch.
Guess what loves eating bagworms? The humble sparrow! Try a few tricks to attract birds to your yard, such as a birdbath, planting seed-bearing flowers like sunflowers, and keep cats out of your yard.
When the infestation requires more than hand-picking or other natural methods, you may want to consider an insecticide containing an ingredient like diazinon or carbaryl. These can be purchased online or at your garden center.
You will need to spray in late spring, just after bagworms have hatched but before they get too large. It is important to wear masks and gloves when applying chemicals. Never apply on a windy day or with children or pets present. Always follow the manufacturer's instructions and apply early in the morning or at dusk to minimize damage to the leaves. Reapplication is almost always necessary.
The bacteria Bacillus thuringiensis (Bt) can also control bagworms if applied as soon as the eggs hatch. You have to apply it before the larvae get too big, so act quickly with this one! You’ll likely need to apply two applications, about ten days apart.
Unfortunately, there is no way to guarantee bagworms won’t reinfest your trees or shrubs. However, if you’ve successfully treated your yard for bagworms, your best tool against reinfestation is to stay vigilant. Regularly check for signs of infestation and take immediate action if you see a return.
By creating a healthy garden environment for your trees and shrubs, you can prevent stress on your plants. Stressed plants tend to entice other pests, making them more susceptible to infestations and weakening their ability to bounce back. Use native flowering plants to attract pollinators, birds, and other garden helpers, and keep your soil well-balanced and full of nutrients.
If you see an infestation return, or if you just can’t get rid of them yourself, it’s a good idea to consult a pest control professional.
As long as bagworms are actively feeding, it’s not too late to spray the area. However, if a bagworm has completed its feeding cycle, it is too late to spray, as the bagworm will have retreated into its thick bag and the spray will not penetrate it at this point.
Bagworms love juniper, arborvitae, spruce, pine, and cedar trees, but they will also nest in various shrubs and plants.
Yes, if you catch them early enough. If bagworms eat more than 80% of a tree, it will most likely die. Early detection is key to helping your tree recover from these harmful pests.
