In the last week or two, we’ve had quite a few calls in the Extension office about Joro spiders. I even joked with my staff that I’ve allowed two to build webs on my back porch so they can catch mosquitos and I can enjoy sitting outside as we head into fall! These spiders (and bugs in general) are pretty abundant this year, so I thought it’d be a good time to update our community on what they are, where they came from, and what you can do about them.
The Joro spider, Trichonephilia clavata is an invasive species native to Asia and Japan. In 2014, the first Joro spiders were found in the United States in Northeast Georgia – by 2022, those spiders had spread about 75 miles in each direction. Today, they are widely found in our area, and most likely here to stay and will continue to spread throughout the U.S.
Joro spiders follow a similar life cycle to other arachnids, starting as an egg laid in the fall, hatching in April and May, maturing and growing over the summer, then mating and laying eggs (up to 400-500) in silk-covered masses in the fall. Immature spiders are small and drab in coloration, which can make them hard to identify. By mid-summer through August, female Joro spiders become easy to identify. They are larger than males, with an abdomen about an inch long and legs that can extend up to three inches. Females are also quite colorful – black, yellow, white, red, and blue on their abdomens, with yellow and black banded legs. Male Joro spiders are much smaller in size, and much more muted in color – think browns, blacks, and yellows – you may not even realize they’re the same species. In addition to their physical characteristics, Joro spiders produce impressive webs of thick, strong yellow silk that’s extremely sticky. These webs can extend 10 feet or more, with some strands reaching over 20 feet between supports like trees or porch columns.
We’ve seen a lot more Joro spiders and other insects this year, and scientists believe that’s due to the warm spring and wet summer we had. These conditions allow insect eggs to hatch earlier in the year, and also causes greater abundance of food resources. Early hatching and lots of food means more numbers and larger spiders overall. Unfortunately, we still don’t know very much about how Joro spiders affect our local ecosystems. What we do know is these spiders are typically very timid, choosing to avoid human contact as much as possible, and while they can bite to defend themselves if needed, it is very rare. It’s safe to say, they’re not a big concern for humans at this time.
If you’d like to do something about the Joro spiders, there are a few options. We recommend removing spiders from pollinator or flower gardens and bee hives, as the spiders will eat our beneficial pollinator species, and we don’t want that to happen. Otherwise, we recommend you remove or kill spiders that are in inconvenient locations – not all of them. Destroying a web or moving the spider is not typically very effective, but can be a kind option if you’d just like them out of the way. If you’d like more permanent control, the best option is to wrap the spider in it’s web using a broom, rake, or stick, and step on it. There are a couple of insecticides designed for spiders that are effective and work on contact. If you’d like a specific product recommendation, check out UGA Publication 1280: Managing Joro Spiders in the Landscape to hear what they tested and recommend. Other options, like those pest control companies might use, are area-wide sprays or fogging, which will kill other insects, not just the Joro spiders – so we recommend avoiding those if possible.
Joro spiders are here to stay, unfortunately, and while they can be a bit of a nuisance with their large webs, they’re also rather striking to look at. If you need assistance with these or any other insect pests, feel free to contact us at rlstew2@uga.edu or 706-359-3233.
