Ridding Playground Of Hobo Spiders

Asked September 19, 2019, 2:30 AM EDT

My daughter’s preschool has a natural, landscaped outdoor play yard covered in bark chips for safety and includes some logs for balancing, jumping and encouraging creative play. A hobo spider with its funnel web was found under a log and my daughter is obviously concerned for her students’ safety. No pesticides have been introduced in this space — again, for obvious safety. How should she approach eliminating the hobos as best she can?

Multnomah County Oregon

1 Response

Thank you for your question.

Because hobo spiders (which are uncommon in Oregon) look very similar to many common spiders, it is difficult to confuse species. Also, many people assume that hobo spiders are venomous in ways that are harmful to humans, but research shows that this is not the case. For more information, please refer to this paragraph, from an OSU document on managing spiders (posted at http://osu-wams-blogs-uploads.s3.amazonaws.com/blogs.dir/2946/files/2017/07/Detailed_Spiders.pdf).

"The hobo spider (Tegeneria agrestis, renamed in 2013 to Eratigena agrestis) was introduced to the Pacific Northwest United States in the 1930’s, and populations subsequently expanded throughout the region. The hobo spider is a large, brown spider that is easily and often confused with other funnel weaving spiders found in Oregon.5,6 The hobo spider is far less likely to be encountered than similar looking species (the domestic house spider and the giant house spider) in most parts of Oregon. Careful, close examination is required to tell the hobo spider apart from these other species. Not only is the hobo spider less likely to be encountered in Oregon than similar looking species, but research shows that hobo spider bites are highly unlikely to cause necrosis either due to venom or antibiotic-resistant bacteria. 2,7 In one U.S. study presented in 1987, the hobo spider’s venom was said to cause necrotic skin lesions in humans. Since then, however, numerous studies examining hobo spider venom have been unable to show skin necrosis. An analysis of patients claiming to suffer from spider bites found over 30 different health conditions associated with skin necrosis that patients or their doctors falsely attributed to spider bites. Research also shows no significant difference in chemistry between the venom of hobo spiders from their native Europe (where their bite is not a reported problem) and the venom of hobo spiders collected from Oregon and Washington. Lab studies likewise show no effect of hobo spider venom on mammalian red blood cells. Numerous spider experts have concluded that hobo spider venom does not cause skin necrosis, and cite misinformed medical professionals and urban legend as perpetuating this myth."
Given the low probability that the spider is a hobo spider, and the lack of evidence that hobo spiders harm humans, PLUS the high risk of harm associated with using pesticides around young children (see http://npic.orst.edu/health/child.html for more information), I would suggest the following lines of action.

1) If you know that the spiders are associated with the logs that are being used for creative play, temporarily restrict play opportunities on these sites. Spiders like logs and other structures, because they provide good protection and anchor points for spider webs. Your daughter's pre-school may want to consider permanently removing these types of materials from the outdoor play yard, if the problem persists. Otherwise, put up flagging tape or another visual barrier, to signal that the area is 'off-limits' for play.

2. Consider using this incident as a teaching opportunity. Students can learn more about spiders (they're really cool!), and can also learn that they should not poke a spider web, or grab spiders, or otherwise do something that might encourage a spider to bite. Most spiders are extremely docile, and will not aggressively attack, unless provoked.

3. If someone can capture one of the spiders, and bring it to your local extension office, we can verify whether it is or is not a Hobo.

4. If a student or teacher is bit by a spider, wash the area that was bitten, and apply antiseptic. Ice can help reduce pain and swelling. If a bit from a black widow, brown recluse, or another spider of medical concern, Seek medical attention, and bring the spider that bit you to verify the species.

Please let me know if you have additional questions or concerns.

Take care,