David Coyle, associate professor of forest health and invasive species at Clemson University, recently co-authored two papers addressing some key public concerns of the public when it comes to Joro spiders.
Joro spiders are large, colorful spiders native to East Asia, but have become common in Upstate South Carolina and are spreading across the Southeast.
The first paper, titled “Chemical management strategies for the invasive Joro spider,” will be published soon in the Journal of Economic Entomology. It addresses safe products that can be used to eradicate the spiders from around the home, as they commonly spin webs on the outside of homes in places like porches, carports, decks and landscape plants.
Coyle and a team of co-authors from Clemson, Southern Adventist University and Union College tested various products, some of which are labeled as spider killing products, while others came from scouring the internet to see what people were telling others to use, such as water, isopropyl alcohol, foaming dishwashing detergent, window cleaners, bleach, hair spray, vinegar and WD-40.
Those labeled as insecticides were effective in killing the spiders. Coyle said that while some household products did kill the Joro spiders, he would not recommend using them.
“They are not labeled as insecticides, therefore it is illegal to use them as such,” Coyle said. “Beyond that, it is not safe, both from a personal standpoint, or ecologically. It’s not good to be spraying machine lubricant or some household cleaner all over where your dog or child might be playing. We strongly encourage people if they must use an insecticide, use a labeled, legitimate one.”
The study was led by Angela Chuang, who at the time was a postdoctoral researcher in Coyle’s lab. She has recently begun her new role as assistant professor at Washington College in Chestertown, Maryland.
“We hope these studies teach people some of the do’s and don’ts around managing these spiders and go a long way towards alleviating any personal safety and health concerns around them,” Chuang said. “If people wish to remove these spiders from their property, we emphasize that manual removal without resorting to chemicals should be considered first, to avoid collateral damage and risks to native wildlife, pets, and people.”
The second paper deals with the aggressiveness of Joro spiders and how bad are its bites. The results of that study will soon be published in the Journal of Medical Entomology. It is titled “Keep calm and carry on: Bites from Trichonephila clavata are unlikely and cause minimal discomfort.” The study was led by David Nelson, a professor at Southern Adventist University.
A year ago, Nelson said he was attending a venom conference and was speaking to reporters who were writing stories on the Joro spiders spread to the Northeast. The spiders had just been spotted in Boston.
“Every conversation ended the same way: What can people do about these spiders? And, are they dangerous?” Nelson said. “I thought, ‘These are relevant questions we can easily address.’ Luckily, we had a fantastic team, including undergraduate to senior researchers, that jumped onboard and we are now able to shed some light on these questions. These spiders may be big, but they would much rather run away from you than bite. And if someone is careless enough to get bitten, the symptoms will likely be milder than a mosquito bite.”
First, a series of interactions with the Joro spiders were conducted, from touching the web, touching the spider, poking it, squeezing it. In most cases, the spiders either ran away or did nothing.
For the second part of the study, the researchers forced the spiders to bite volunteers, who then ranked the pain based on the Wong-Baker FACES Pain Rating Scales, a pain assessment used in pediatrician offices where six faces ranging from a neutral expression (no pain) to a crying face (worst pain) are used to identify the pain level.
“We asked participants their pain level at several time points,” Coyle said. “It was never more than a 4 for anyone. Most were in the 1 range, which would be similar to a mosquito bite to most people. We also measured redness around the bite. Our conclusion was that Joro spider bites don’t do much and it doesn’t hurt most people.
The message to the public is simple, Nelson said.
“These spiders are easy to manage and pose a minimal health risk,” Nelson said. “Spiders have a bad reputation, but the vast majority of species are not capable of causing physical harm. And, the few that are medically relevant are generally non-aggressive. A little bit of common sense (e.g., check your shoes before putting them on if you live in an area known to have a potentially dangerous species) goes a long way in preventing a bite.”
Coyle said the study could be the first controlled bite study of its kind.
“Although the thought of interacting with and managing Joro spiders might seem scary, we also showed that bites are unlikely and have minimal effects,” Chuang said. “While the extent of the ecological effects of Joro spiders on native spiders is still being investigated, it is reassuring that their human health impacts seem minimal.
“We hope this can be a useful study for medical health professionals seeing patients with suspected spider bites.”
