Tag Archives: chemical

How to protect yourself from ticks

I spend a lot of time outside, sometimes face-down in the weeds trying to get a photograph of something small. So I have some opinions about tick prevention and thought I’d share.

blacklegged (deer) tick on sock
Ixodes scapularis
  1. Spray or soak shoes, socks, pants, shirts, hairband, hat, etc., with permethrin (buy online or at outdoor stores), then let dry before you using. Chemical only slowly washes out so you only need to reapply every 5th laundering or so (or after 5 months if you don’t wash your clothes). Spray your backpack with permethrin, too, because you likely set that on the ground during breaks. Do not spray permethrin on your skin. You can also buy clothing that comes pretreated with permethrin.
  2. Spray your clothes and skin with DEET, picaridin, para-menthane-3,8-diol, IR3535, or 2-undecanone. DEET really is the best. Note that “pure” oil of lemon eucalyptus (extracted from Corymbia citriodora) is not currently recommended by the CDC; the oil has small, variable levels of para-menthane-3,8-diol but apparently not enough. All of these repellents do not last like permethrin so reapply every few hours. Do not spray DEET on anything plastic (it will melt).
  3. Be suspicious of “natural” or “organic” concoctions that claim to effectively deter ticks. If one of these recipes actually works the CDC would recommend it. I’ll update this page when that happens. Similarly, avoid apps, crystals, and dietary supplements. If you need help convincing a friend to just use DEET (it’s super safe), mention that DDT is a different chemical that just happens to start with the same letter. DEET is also gluten and GMO free.
  4. Wear light-colored clothing so you can better see ticks. Like this person. Note that this strategy fails with tick larvae because they just too small to see unless you are wearing something pure white and have really good vision.
  5. Tuck your pants into your socks. Like Kanye West. You can even buy tick socks that are treated with permethrin and have a tight weave that prevents larvae from burrowing through the fabric.
  6. Wear tall, light-colored, glossy boots that ticks can’t easily climb. I suspect that larvae and nymphs can still climb glossy surfaces, though. I own a pair of Muck Boots and they have a neoprene surface that I suspect ticks can easily scale. I’m considering switching to something like a Gumleaf boot.
  7. Buy some gaiters and treat them with permethrin. Some gaiters are even designed to keep out ticks. Some even come in lime green. (NB: Lyme disease is named after Lyme, CT.)
  8. Buy some arm sleeves. Like gaiters, you can even buy ones that are already infused with permethrin.
  9. Shave your legs.
  10. Keep checking for ticks as you hike. If you are hiking with others, scan them for ticks, too.
  11. Keep a roll of duct tape handy so that you can easily remove ticks. Travel-sized lint rollers are good, too, and easily attach with a carabiner to a backpack.
  12. Put your field clothes into quarantine when you come home. Ideally, launder them immediately. Ticks can wander off of clothing and backpacks and show up later.
  13. Get naked and check for ticks. Everywhere. This is a really good reason to get a girlfriend or boyfriend even if you’re not really into them. Don’t tell them that.
  14. If you have limited neck mobility, invest in a nice automotive inspection mirror so you can see all the various parts of your body you never look at. You can even buy lighted ones. You can also use a selfie stick and a smart phone, but that’s risky if you accidentally forget to delete the photographs and video.
  15. You probably don’t want to know this but ticks are fond of lodging in ears. Get yourself an otoscope if you feel something in there. You can even buy phone attachments to get pics.
  16. If you find a tick that is attached, take a photograph (like this) then remove the tick. Carefully. I have a Tick Key (see one in action) but there are lots of types. Then take photographs of the bite location and of the tick. If you live in Pennsylvania, send the tick out for free testing. If you live elsewhere, put the tick in vodka or in the freezer in case you need to get it tested later.
  17. Take a long hot bath with a lot of soap. Ticks are hardy but you might dislodge an unattached nymph that somehow got past your first-line defenses.
  18. Once you are de-ticked and clean and have the laundry running, post photograph of tick on iNaturalist so you can get an identification. Here are the ticks of North America on iNaturalist. You can also send pics of ticks to TickEncounter for ID.
  19. Monitor the attachment spot closely. If a red spot appears, take daily photographs with ruler in frame so that doctor can assess progress of redness. Here are pics of Lyme rashes. You can even mark the progress with a Sharpie. There are plenty of other diseases transmitted by ticks, though, so don’t rely on rashes.

Alternative lawn signs for Mosquito Shield

Mosquito Shield is just one of dozens of companies that spray pyrethroids to kill mosquitoes. Homeowners typically pay $800 per summer for treatments spaced every 21 days and, as part of the deal, agree to feature a sign in their yard for the season.

Two types of people have these yard signs. The main category is homeowners who fully understand that pesticides have bad environmental effects but who simply don’t care. These are likely the same people who knowingly drive with their high beams on at night (“It’s safer for ME!”). And then there are people who were duped by the pesticide companies into believing pyrethroids kill only mosquitoes.

To better reach this second type of person as well as those who are interested in mosquito sprays but are still on the fence, I’ve fabricated six signs that highlight the fact that pyrethroids kill other animals:

All the signs are fairly self-explanatory except for perhaps the Bird Shield one. Pyrethroids don’t kill birds directly but many species depend on insects and spiders to feed themselves and their young. So when you hire Mosquito Shield to nuke your yard every three weeks you are reducing the numbers of birds that can survive in an area.

I realize that none of the above signs is going to be used by an actual pesticide company. Their business model is to obfuscate about the effects of pyrethroids. Indeed, most companies try to hide the fact that their mosquito sprays even contain pesticides. That’s why the government (federal and/or state) should require companies to clearly indicate the active ingredient of the spray. Here’s how it could (should) look, thus allowing curious neighbors to Google the chemical and be horrified.

Pyrethroid sign for Mosquito Shield

If you are an influential part of a local government, please consider enacting an ordinance that requires disclosure of the pesticide name on signs.

If you need an individual sign for your a presentation, here are some image files: fireflies, butterflies, bees, spiders, fish, birds.

Please share this page on your neighborhood social media to get the word out. These companies are spreading in popularity and it’s horrifying.

More details here.

Effects of mosquito sprays on humans, pets, and wildlife

Mosquito Authority, Mosquito Joe, Mosquito Platoon, Mosquito Shield, Mosquito Squad, TruGreen, and many other companies often imply that the insecticides they spray on yards are safe for everything except mosquitoes. These companies are also very reluctant to reveal what chemicals they use. This page contains information on what, exactly, they spray and what effects those chemicals have.

After a little digging, I think I’ve uncovered most of the active ingredients used by these companies:

Please email me if you think I’ve made an error or if you know that a formulation has changed (which happens). All of the chemicals are either pyrethrins or pyrethroids, which are natural and synthetic (respectively) neurotoxins that cause almost instant paralysis and death to mosquitoes. Below is the chemical structure for one, permethrin:

Are these chemicals safe for humans?

Pyrethroids are relatively safe but should not be viewed as harmless. If you spill enough on your skin you might experience itchiness, numbness, nausea, and respiratory problems, among a rather long list of adverse events. Although you obviously can’t test whether pyrethroids harm human brains, studies on mice and rats suggest that the chemicals do act on mammalian nervous systems; that should at least give you pause if you have kids rolling around on the grass after the yard gets dosed. Indeed, there is at least one correlational study that suggests exposure to pyrethroids is not good for kids (or at least boys). There are also scattered reports that some pyrethroids are carcinogenic and estrogenic but I don’t think such effects are shockingly large, and to date they seem to be restricted to mouse studies. At very high doses pyrethroids can kill you, a fact known because some people have injected it (suicide) and in one case because somebody ate food that was cooked in pyrethroid concentrate (it resembles cooking oil).

Are pyrethroids safe for pets?

Dogs and chickens seem to be fine. Cats, however, lack sufficient levels of a liver enzyme that helps detoxify pyrethroids and can thus develop what is called pyrethroid toxicosis. A good indicator of cat sensitivity to pyrethroids is the standard warning of keeping cats away from pyrethroid-treated dogs. I.e., if you dose your dog with a large amount of pyrethroids (to kill fleas, e.g.), cats that cuddle with the dog are at risk. If you’d like to see a video of rag doll cat with pyrethroid poisoning (you probably don’t), here’s a video.

Do pyrethroids kill other animals? 


For example, the spray kills monarch caterpillars, even weeks later later due to the presence of insecticide dried onto milkweed leaves (Oberhuaser et al. 2006).

And the spray can kill honey bees, even if honey bees are inside their hives when the pyrethroids are spayed (workers bring small amounts back to the hive the following day if they land on treated plants or if they find small puddles of water to drink). Sublethal amounts of pyrethroids can change honey bee behavior and make workers smaller. I would imagine the pyrethroids would end up in the honey, too.

And pyrethroids kill fireflies, which are most active in a yard in the late evening when mosquito-spraying franchises like to fog.

My favorite group of unnoticed insects that are killed by evening pyrethroid applications are solitary bees, of which there are approximately 4,000 species in the United States. These are bees that collect pollen and nectar during the day but spend their evenings and nights in holes (e.g., mason bees) or clamped to low vegetation. E.g., look at this a two-spotted long-horned bee (Melissodes bimaculatus) from my front yard this summer. Everyone has dozens of species of native bees in their yards but few people realize it. So when pesticide applicators claim their pyrethroid sprays “don’t harm bees” or are “bee friendly”, that is entirely untrue. It’s simply a marketing slogan they were taught when they bought the franchise, and they will insist it’s true even when presented with evidence to the contrary.

Anyone using a spraying service is, therefore, killing all of the above and more. Insects are small and easy to ignore, but if you were to go out after a spraying and look very carefully, you’d find thousands of dead insects on the ground. And only an extremely small percentage would be mosquitoes.

Pyrethroids can kill ALL arthropods, in fact, not just insects. So if a yard is sprayed, likely you’d likely find dead spiders, mites, centipedes, and millipedes.

One obvious consequence of gassing all the arthropods in a yard is that bird species that eat arthropods will have a lot less to eat. Population levels of swallows and flycatchers, for example, have dropped in last several decades and one explanation is that there are fewer insects to eat.

And then there are fish, which are acutely sensitive to pyrethroids. Franchise owners will generally avoid spraying near people’s fish ponds and bodies of water. Indeed, by law pyrethroids can’t be used near water, though there are many reports of franchises ignoring that regulation. Even if a property doesn’t have a pond or stream, pyrethroids are rather stable in the soil and tend to get washed into nearby streams after rains. It is increasingly accepted that runoff of pyrethroids into creeks can kill fish downstream.

Finally, pyrethroids are toxic to certain earthworms. This is probably especially true for those species that come out onto lawn surfaces in the evening, when pyrethroids are often applied. To be honest, many people don’t really care about earthworms (some hate them) but for people who love aerated lawns it should be pointed out that fogging with pyrethroids might result in less aeration. And, perhaps, result in robins that wonder where all the worms have gone.

Pyrethoids are engineered to last for weeks

As mentioned above, pyrethroids adhere to plant surfaces and stay chemically active for weeks, so the risk to all the organisms mentioned above can last for weeks. Here’s a a description of pyrethroid persistence that I found on a Mosquito Squad FAQ:

“How can the barrier spray continue to kill mosquitoes for 21 days? Mosquitoes will feed on plant juices. When they attempt to feed on sprayed leaves, the residual from the spray will kill them.

Mosquitoes don’t eat leaves, of course, but the quote is correct about the fate of insects that walk on treated leaves. Pesticide franchises like to claim that once their product is dry it is no longer toxic, but that claim makes no logical sense in light of their claim that the product provides protection for three weeks. Some pyrethroids can even last for 90 days if they are on shaded surfaces.

Signage and notification requirements

There doesn’t seem to be a Federal law requiring either signage or neighbor notification when a yard is sprayed with insecticide, and state laws are variable (here’s a good review; here’s another). Many states have laws that require applicators to leave signs at properties that have been sprayed, and some require notification of neighbors prior to spraying. For example, most counties in New York require that neighbors be notified 48 hours before spraying (details). That’s also an option for beekeepers in some states, too; in that case the pesticide applicators need to search a database of hives in a town, then notify hive owners when spraying will happen.

I live in Pennsylvania, one of several states that allows people to be placed on a Pesticide Hypersensitivity Registry. Once on it, pesticide applicators will know you have a medical issue with pesticides and they are obliged to inform you of future spraying (so you can leave the area).

If you want to know what rules might apply in your state, Googling “pesticide notification laws regulations residential pennsylvania” (replace with your state) will get you started. If that doesn’t help just contact your state agency that regulates pesticide use. Towns and cities will sometimes have their own rules but some states prohibit such rules.

How local governments can help

All towns and cities should maintain a web page that provides mosquito information and relevant pesticide laws to residents. Towns can also enact ordinances on third-party pesticide applications. For example, a town might require that franchises alert neighbors 48 hours before spraying is done.

State governments can also make sure that pesticide franchises are not making false claims. E.g., if companies claim through words or imagery that their pyrethroid-containing sprays are “environmentally friendly,” “bee friendly,” “kid friendly,” “pet friendly,” or government approved (e.g., “EPA-approved”), sue them. Massachusetts did, and now has several restrictions on advertising including a ban on ads that “rely on images of young children to convey a sense of harmlessness“. Almost all sites I’ve looked at have misleading wording, especially the claim that pyrethroid-containing sprays “target” mosquitoes and ticks (completely false; they do no such thing). 

Is spraying effective?

Although spraying pyrethroids might be a good way to kill mosquitoes near the ground and in low shrubs, many mosquito species spend most of their time high up in the canopies of trees and are untouched by sprays. For example, many species in the genus Culex (transmitters of West Nile virus, St. Louis encephalitis, eastern equine encephalitis, western encephalitis, avian malaria, etc.) are tree dwellers and only occasionally come down to feed on humans and pets. This limitation isn’t just theoretical: one study showed spraying didn’t reduce numbers of Culex at all. So if you have trees and birds, don’t expect that spraying will be effective.

But I don’t want to imply that spraying is completely ineffective. Pyrethroid fogs will probably kill a large percentage of Anopheles spp. (vectors of malaria) and Aedes spp. (vectors of dengue, yellow fever, Zika, etc.) because these species are more likely to be lower in the vegetation.

Do garlic sprays work?

Many pest-control companies offer a garlic-based spray, too. I haven’t been able to find any scientific publication on these sprays. They might work. But they might also just cater to people’s hopes. Ask the company for printed efficacy data and pass if all they give are testimonials and promises. If you know of a peer-reviewed article showing that garlic spray kills and/or repels mosquitoes, please contact me and I’ll include here.

Automatic fogging systems

For about $4,000, some companies will install systems that dispense pyrethroids over your yard at regular intervals. Don’t do this. Just don’t.

Alternatives to spraying

Here are my tips.