Joro Spider Update: controlling this invasive species

Joro spiders are EVERYWHERE! If you live in North Georgia you are bound to run into one of their webs as soon as you step outside. Removing their webs from our patio area, walking paths and amongst the shrubs is a daily chore. Their webs are strong and multi paneled and can be found from the shrub layer to high up in the tree canopy. The three layered web has one central orb with two asymmetrical layers on either side. The sticky silk captures all manner of insects and are strong enough to catch hummingbirds, small bats, tree frogs or lizards. 

We found the first Joro spiders in our garden four years ago. You can read my post about their discovery here. These spiders are a non-native species [from Asia] that have multiplied astronomically since they landed on our shores. They spread rapidly because they travel easily using a ballooning method where they catch wind currents with a strand of their silk. In just eight years, they have spread to at least 23 counties in Georgia. 

Male & Female Joro Spider

They are not [yet] officially classified as invasive since studies are currently underway to scientifically determine their impact on the local environment. But we know that many introduced species impact the native species and will upset the balance of the local ecosystem. 

Generally, we view spiders as beneficial and welcome them in our garden. Just like other predator species, spiders serve an important role in the ecosystem, controlling insect populations. They also serve a vital link in the food web as a crucial protein source for birds, lizards, wasps and even other spiders. So what is the problem with Joro spiders? 

Female Joro spider with European honeybee

They do make an impact on insect populations, especially those that most people view as pests. In fact, they will prey on another non-native insect, the brown marmorated stink bug, that our native spiders won't touch. The Joro spider can also be food for mud daubers and other wasps. 

female Joro spider capturing a two lined spittle bug

The issue is that they are competing with our native garden spider and other spiders in the orb weaver family for food. Sadly, this year we haven't found any yellow garden spiders (Argiope aurantia) on our property. Is this because of the introduction of the Joro spider? Scientific studies will provide more data in the coming years but my anecdotal observations say yes.  

Joro spider seizing a Eastern Tiger Swallowtail butterfly

These non-native spiders are feeding on our native insects, and with the Joro spider's large numbers, it appears they will further reduce our native insect population, which is already in peril. I'm a believer in letting nature maintain a balanced ecosystem in the garden, leaving predaceous insects and insectivorous vertebrates to provide environmental regulation. However, when a non-native species is introduced, this can wreak havoc on the biome.

So we are intervening by removing the Joro spider webs that are reachable with a broom or stick. When possible, we also kill the spiders by stomping on them. But be prepared as they move quickly and when you take down a web containing multiple spiders you need to act quickly. Early September is when these spiders reach maturity and will die by late November, but not before leaving egg sacs filled with 400-1500 eggs that will hatch next year. If you find an egg sac and are able to positively identify it as one from a Joro spider and not a native spider, it can be destroyed. Our efforts may only make a small impact on their numbers, but hopefully we are saving many pollinators and other native insects from being captured.

Comments

  1. Yikes - sounds likes something out of a horror movie! It's particularly scary that you haven't seen any native garden spiders. If the Joro spider is ultimately considered invasive, is there anything that can be done?

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    1. Unfortunately, they are here to stay. Sadly, not much to do once an foreign species has been introduced. There isn't a good way to remove them without harming native insects.

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  2. Karin, we hunt them everyday on our deck and front yard. By using a bug zapper, at least it makes it kinda fun. Electric bug zapping racket on Amazon.

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    1. Great idea Penny! Much easier than chasing them down with a broom.

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    2. Wow! I had to look at some other articles after you posted because I was unfamiliar with them. It won't be long before they are throughout the south. :(

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    3. Unfortunately, I think you are correct. They are spreading at a rapid pace.

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  3. I will have to look at my spiders a little closer!

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    1. Hopefully you don't have them yet, but they will make their way to area at some point. It is important to look at them closely before you kill them to confirm they are Joros because the native Golden Orb Weaver has the same coloring and patterns on the legs.

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  4. Do you have any photos of the joro egg sac or advice on how to distinguish it from those of native orb weavers? I am thoroughly disgusted with these creatures, I’ve watched them kill two local garden spiders and a hummingbird just this year in my own yard! I want them GONE.

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    1. The spiders wrap the silk around them so they will be a yellow/gold color which is different than our native orb weavers. My experience is that they lay them close to their webs. I have found several on the house and removed them. I will try to remember to take a photo next time I find one and send it to you.

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    2. So, while i love that kill stink bugs, the overall detrimental effect of Joro's is less native species. Regardless of what studies are being done to determine if they are considered invasive, the fact remains, no natural predators are in GA to stop the population explosion. Scientific studies are needed as a way to find facts, but when year after year, this spider is becoming the only spider I see in my yard and garden, then seeing is the only fact I need to do my part and kill everyone I see.

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    3. I have been trying to find pictures of a sac as well. They have built their web in areas we often step out without thinking to look for a web... well it just so happened that I wanted to put a trash bag in the bin just outside our side door from the garage.. and oh looky... she was there blocking me and luckily being at my eye level I saw her right away.. but my kids could have easily walked into it... and just today another one just above our gate to go down the stairs from our back porch... well no more for these and some others (around the trampoline and front porch) wasp spray is the solution for us... and then remove the complete web with all kind of other little webs closed by and hope we got the sac... yes, now when we open a door to the outside we check first before stepping thru... good luck everyone... there are in the powerlines everywhere here in Cumming GA and some of them span down to the bushes on the ground... creepy!!

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  5. I'm thrilled about no longer having invasive stink bugs, miserable biting flies, house flies, etc things like that on our property since the invasion of the joro spiders. I am concerned about the pollinators though. And the hummingbirds and monarch butterflies.

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One of my favorite things about blogging is the conversation with readers. Leave a comment and let's get talking. ~Karin

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