Bizarre Pinecone-Shaped Cocoons Are Invading North America, And You Should Drown Them
The next time you see what appears to be a pinecone hanging from a branch, it might be worth taking a closer look. That's because cocoons that look almost identical to pinecones are appearing on trees throughout North America - and they're definitely bad news.
These cocoons aren't an alien invasion or anything, but they do contain eggs of the bagworm moth. These eggs, once they hatch, can cause serious damage to trees, even to the point of killing them. Let's talk about how to handle these cocoons.
The cocoons look a lot like pinecones.
A close look shows that they're not exactly indistinguishable from pinecones, but if you're looking at them from a distance, your brain would probably register them as pinecones - they're brownish, rough-textured, and hang from trees.
One of the biggest giveaways that these aren't pinecones is that they can be seen on both coniferous and deciduous trees. While coniferous trees like evergreens do have pinecones, they're never seen on deciduous trees.
The cocoons are made with a variety of materials.
The bagworm moth, in its larval stage, will create these cocoons using a combination of materials: silk (they are moths, after all) is spun together with various organic material found in and around the tree.
This is part of the reason that these cocoons are so camouflaged and have an organic appearance: the exterior that you're seeing is mostly organic material, as it's composed of tree bark, twigs, and assorted bits of leaves and other debris.
Why are they a problem?
Not all moths or cocoons are seen as a nuisance, but the bagworm moth can be particularly destructive. When kept in check, they're not such a big deal, but they can be serious pests in some cases.
When bagworm numbers are on the rise - and they're definitely on the rise right now in North America - they can spread between plants and attack trees, eventually killing them in many cases.
The cocoons contain hundreds of eggs.
Hundreds of eggs means hundreds of potential bagworms, and hundreds of potential bagworms means the potential for hundreds of cocoons. The numbers rise exponentially as more and more of these pesky pests hatch.
Not every single egg is going to be viable, of course - but the numbers mean that it's tough to be confident that you've fully ended a bagworm infestation, as that would require killing thousands of eggs in total - and the survival of just a few could be an issue.
There are a few ways to kill them.
If an infestation is detected early enough, it's possible to simply pluck the cocoons from the tree (just make sure you get all of them!), which should keep the tree itself safe.
Other than picking them from the tree, insecticides can also be a way to keep these infestations in check. But these insecticides can be expensive, and also damaging to not only the tree, but all sorts of useful organisms within it.
They can destroy a healthy tree in a matter of weeks.
Because bagworm populations are surging in North America, they're now present in many areas that haven't hosted them before. That means that, for people who are unaware of the problem, they aren't likely to notice the infestation until it's too late.
An infestation can see bagworms eating away at the leaves, needles, and bark of trees - and a once-healthy tree can be essentially reduced to kindling in just weeks or months.
Best practice is to drown them.
Plucking them can work and insecticides can work - but if you want to be absolutely certain you've killed every possible bagworm egg, the best way is to pluck them (thoroughly), and then drown them.
Some people have even reported that they boil the cocoons as well, just to be extra sure that everything within said cocoon is dead and won't hatch into more of the harmful little critters. Aside from boiling, you can also put them in a mixture of water and dish soap.
They're born to be pests.
Male bagworm moths, once they emerge into their moth stage, can fly around freely. Adult females don't have wings, so they generally spend their life cycles inside the cocoons that are seen on trees.
With females living in the problematic cocoons and males flying around freely, it's no surprise that infestations can grow exponentially once a given area has a certain number of bagworms present. It's obviously a tough problem to contain.
Different species cause different issues.
While most of the recent news surrounding bagworm damage is coming out of North America, these moths have been causing damage all around the world. The wattle, or acacia, tree of South Africa is especially vulnerable to bagworms.
In fact, some cultures cultivate a certain number of bagworms because, despite their destructive impact, their protein-rich pupae serve as an excellent source of food.
Orange trees are vulnerable, too.
In the northern stretches of the United States and Canada, bagworms are causing problems with both deciduous and coniferous trees. Further south, in Florida, bagworms have become serious pests when they attack orange trees.
In order to grow juicy, delicious oranges, it's especially important for these trees to remain pest-free. But with bagworm numbers surging, it's becoming more and more difficult to ensure that orange groves are entirely free of these pests.
They emerge in the spring months.
Cold weather has a destructive effect on bagworms, as it can kill the eggs within the cocoon. But with winter temperatures on the rise in once-chilly areas, more and more of their eggs are surviving into the spring months.
Once the weather gets warm enough, the eggs will hatch - just in time to feast on, and destroy, the new leaves and buds that are growing on their host trees.
They do have some natural predators.
Bt, the bacteria Bacillus thuringiensis, can be applied to bagworm cocoons. If done early enough, it should kill any larvae that hasn't progressed past a certain stage. There are also a few non-bacterial predators.
Birds like sparrows also enjoy feasting on the juicy bagworm larvae. But because we can't really control birds, we also can't rely on sparrows to effectively keep a bagworm infestation under control. It is possible to attract sparrows to your yard by giving them shelter and water.
You can try neem oil as well.
Neem oil comes from the pressed fruits and seeds of the neem tree. Where it comes from doesn't matter so much as what it does: suffocate young insects like bagworms, hopefully preventing them from reaching maturity.
While drowning cocoons is effective, you can be extra-certain you've killed the critters by diluting neem oil in a bucket of water, then dumping the cocoons within. The mixture will be doubly deadly, as the bugs will be totally unable to breathe.
Which insecticides are the right insecticides?
Many people will understandably balk at using any kind of insecticide, for any reason. But if you're willing to go this route, you'll want to understand the best way to deal with your particular infestation.
In general, the best insecticides for bagworm control are acephate, cyfluthrin, and Spinosad. Of these, Spinosad is actually quite environmentally friendly. Applying any of these insecticides, usually via a spray bottle, to infected leaves and branches should help control bagworm populations.
You can opt for trees that bagworms don't like.
Most homeowners aren't in a position to choose the exact species of trees they have on their property, and removal of existing trees can be expensive. But with bagworm numbers climbing, it's worth considering what kinds of trees you might want to plant moving forward.
Bagworms attack a wide range of common trees, unfortunately. But a few species such as morella, holie, and magnolia are generally less attractive to bagworms.
You can drown them - or burn them.
This one might require the help of an arborist, but one way to take care of infected trees is to strategically remove branches and limbs that are afflicted with bagworm infestations. Of course, this requires careful examination of the tree to make sure that only healthy areas remain.
From there, you can throw the diseased branches - cocoons and all - into a big bonfire. Just make sure you do so safely and don't violate any local fire ordinances.
Or you can remove the tree entirely.
This is an option for any tree that's beyond saving, and should only really be considered as a last-ditch effort. On an ecological level, we need more trees - and on a financial level, it's expensive to remove trees.
That said, if a tree is going to die anyway from a bagworm infestation, it's best to rip off the band-aid and just remove the tree. That way, the dying limbs won't serve as a host to more generations of bagworm.
Keeping your yard neat and tidy can help.
Bagworm cocoons are only partially made of silk. That means that the rest is composed of debris that can be easily collected by the little critters - and if your yard is full of random debris, it just means that bagworms have more to work with.
So if you have a lot of yard waste lying around, it's worth bagging it up and disposing it. Bagworms will likely still find stuff to make their cocoons out of, but this at least makes it a little harder for them.
Moths are drawn to light.
Another small thing you can do to control bagworms is to keep your outdoor lights off when you're not using them. Because bagworms are moths, they're drawn to light - so if you keep your patio light on all night, bagworms are going to love it.
You can even take this a step further by making sure your curtains are drawn when it's dark outside, so none of your light bleeds into your yard.
When in doubt, call an expert.
There are many things you can do that will have an impact on bagworms, but at the end of the day, it's very hard to be certain that these pests won't be drawn to your trees and shrubs.
If you want true peace of mind, it's best to call an expert. They'll be able to assess the level of infestation and provide actionable advice for steps you can take to keep things in check.