Trichonephila clavata, commonly called the Jorō spider, is one of the newest invasive species in the U.S., and the spiders’ presence in and around structures, homes, and yards drives a lot of questions about how to manage them and whether they are dangerous to people. Two new studies offer good news: Products labelled for spider control are safe and effective against Jorō spiders, and they are both unlikely to bite and generally harmless if they do. (Photo by David Coyle, Ph.D.)

By David Coyle, Ph.D.

David Coyle, Ph.D.

Ah, fall. Leaves changing color, cool, crisp autumn air, pumpkin spice in so many things that just shouldn’t have pumpkin spice (I mean, pumpkin spice Spam ? Stop it.). And if you’re an extension entomologist in the Southeast, fall also means it’s Jorō spider season.

Trichonephila clavata, commonly called Jorō spiders, are not just spiders—they’re big spiders. They’re colorful spiders. They’re invasive spiders. And they’re in-your-face spiders that tend to make webs (sometimes very large webs that reach 20 feet wide) on homes, landscape plants, and other structures right in the middle of where people live, work, and play. They were first discovered in North America in northern Georgia in 2014 and are presumed to have arrived a few years prior. In those 15 years or so, Jorō spider populations in the U.S. have increased dramatically, and their population now covers much of the Southeast and includes disjunct populations in parts of the northeastern U.S. as well.

In a study examining effective management methods for Jorō spiders, researchers found that several spider control products that are already commercially available worked well. However, they may often not be necessary—the easiest and cheapest way to eliminate Jorō spiders from an area is often simply with a broom or a stick.

The resulting influx of calls from the public to entomology extension programs (and the associated media frenzy) has typically centered on two questions: How can I get rid of Jorō spiders on my property, and are Jorō spiders dangerous? Considering the spiders’ size, numbers, and close proximity to people, these are valid questions. That’s why colleagues at I at Clemson University, Southern Adventist University, Washington College, and Union College embarked on two new studies: One to test methods for eliminating Jorō spiders in or around a home, and one to find out how likely Jorō spiders are to bite a human—and whether such a bite can do any harm. These studies were published last week in the Journal of Economic Entomology and the Journal of Medical Entomology, respectively.

How Can I Get Rid of Jorō Spiders on My Property?

To answer the question of “how can we manage Jorō spiders,” we scoured the internet for recommended treatment options. Why this approach? Well, there just aren’t many spider-specific management recommendations out there. Sure, there are some for the medically relevant ones, like widow spiders and brown recluses, but Jorō spiders do not enter homes on their own, and they’re still relatively new in the U.S., so very little is known about how to manage them.

Using recommended products from the internet and labelled spider control products available at stores, we tested these products to see which ones would effectively eliminate Jorō spiders . We found that while several products will eliminate Jorō spiders, some of these are not legal pesticides (e.g., machine lubricant) and therefore are not recommended. Several spider control products that are already commercially available worked just fine, and we strongly encourage folks to use labelled products .

That said, the easiest and cheapest way to eliminate Jorō spiders from an area is likely to be without chemicals, but with a broom or a stick.

Are Jorō Spiders Dangerous?

Ever walked into a spider web? Or rode your bike and took a spider to the face? It’s not a great feeling, and it apparently happens often enough that a lot of folks wonder if Jorō spiders are “bitey” spiders—as in, if I take a Jorō web to the face, will that spider bite? (And give the bitten superpowers, perhaps?)

In what for me was one of the most unique studies I’ve been a part of, we evaluated Jorō spider behaviors to see how they would react to people . Turns out, they’d rather drop off the web (or your hand) than hang around and bite you—and you really have to provoke them to even get them to bite in the first place.

Plus, thanks to several folks who volunteered to get bitten by Jorō spiders (yes, you read that correctly) we now know that Jorō spider bites are, in most cases, akin to a mosquito bite. A little redness, a little swelling, but largely gone by the next day. And no acquired superpowers were reported.

In a study examining whether Jorō spiders are dangerous to humans, research found that the spiders would much rather drop off a web or hand than hang around and bite a human and that, in most cases, Jorō spider bites are akin to a mosquito bite. (Photo by David Coyle, Ph.D.)

What to Know About Jorō Spiders

Our take-home message from this work is twofold: First, if you have to manage Jorō spiders on your property, the simplest and most effective way is probably to not use pesticides at all; a broom or stick works just fine. But if you feel you need pesticides, we recommend sticking with a product labeled for spider control. And, second, if a Jorō spider does get on you, try not to freak out—it doesn’t want to be on you either, and the odds of you getting bitten are extremely low.

So, enjoy that glorious fall weather outside, drink that pumpkin spiced beverage, but also, you might want to watch where you walk.

David Coyle, Ph.D., is an associate professor in the Department of Forestry and Environmental Conservation at Clemson University. Socials: @drdavecoyle. Email: [email protected].