Tag Archives: control

Spartan Mosquito Eradicator (review)

Spartan Mosquito Eradicators are selling like hotcakes around the country so I bought two and thought I’d share some thoughts. The devices are just black tubes filled with water, sucrose, salt, and yeast, and you hang them at different places in your yard according to instructions that are included. Per the company, mosquitoes are lured to the devices by the CO2 produced by a yeast, crawl inside (through holes in the cap), drink the liquid, crawl back out, then eventually die when their guts rupture. Here is one hanging in my yard:

Spartan Mosquito Eradicator

The science behind the device

There are several reasons why such a device might be expected to work.

First, it is well-established that mosquitoes obtain carbohydrates from decaying (fermenting) fruit, and several studies have shown that mosquitoes are attracted to solutions of sucrose and yeast (Oli et al. 2005, Smallegange et al. 2010, Sukumaran et al. 2015, Dhanique et al. 2017) .

Second, it is well established that mosquitoes can be effectively lured to and killed by sugar solutions that are laced with poisons (reviewed by Fiorenzano et al. 2017).

Third, I’ve heard from mosquito researchers that mosquitoes can crawl through very small holes (e.g., when looking for an oviposition site).

Did they work?

No. I didn’t notice a drop in the number of mosquitoes in my yard. My mosquitoes are largely Asian tiger mosquitoes (Aedes albopictus) and several Culex species. I spend a lot of time outside so I would be in a position to know whether there was a reduction in mosquitoes. The devices simply didn’t work.

That said, the Spartan Mosquito Eradicator is quite effective at killing small organisms other than mosquitoes. Within a few weeks the surface because a bubbling, charnel pit. Some of the visitors clearly lay eggs before they die because you can find larvae writhing around:

Below are photographs and IDs of the some of the insects I’ve found trapped inside. Notable is the presence of spotted-wing Drosophila (Drosophila suzukii), a serious pest of orchards and berry fields. The adults found inside the trap were all dead but of concern is that the females oviposited into the liquid, and one of the traps had living fly larvae. Photographs of all the victims are available on my iNaturalist account.

Below are photographs of insects on or near my Spartan Mosquito Eradicators. I checked the devices probably 100s of times during the summer and I’ve never seen a mosquito on or near them. And I most definitely have mosquitoes in my yard — mosquitoes are just completely uninterested in the devices.

Why didn’t they work?

In my opinion, there are three reasons why the Spartan Mosquito Eradicator is unlikely to kill a single mosquito unless it falls from the tree and lands on one.

First, the holes in the cap are too small (5/32″) to allow mosquitoes to enter, at least with regard to mosquitoes in search of rotting fruit. There’s not a huge literature on what size holes mosquitoes can crawl through, but Dickerson et al. (2018) found that only 1 out of 100 female Aedes aegypti mosquitoes went through an 8-mm hole after 1 hour when presented with a host. So a hole of 5/32″ (4 mm) is likely just too small unless mosquitoes are truly desperate. Furthermore, although a hungry female mosquito might squeeze itself through a small hole in search of a warm mammal (Bidlingmayer 1959), I doubt that they would do the same merely for some rotting fruit, especially if a yard is full of easier sources of sugars (they like flower nectar, e.g.).

Spartan Mosquito Eradicator cap with holes.

I understand that the small hole size is necessary to exclude larger insects like honey bees, but I’m perplexed why something a tad larger wasn’t used. I glanced at the company’s patent application and even there the hole sizes seem too small (3/16″ maximum).

Here’s a video of the device in action (inside an aquarium filled with hundreds of mosquitoes). Below is a screen grab of the video:

A Spartan Mosquito Eradicator inside an aquarium with hundreds of dying mosquitoes.
Frame grab from a time-lapse video of mosquitoes dying inside an aquarium in which a Spartan Mosquito Eradicator was placed.

My guess is that not even a single mosquito in the video entered the device — they just died over the course of several days from starvation and desiccation. It would be nice to know whether the company filmed it exactly as above (with holes hidden) or whether the company cropped out the holes after filming. The company wouldn’t respond when I asked.

Second, sodium chloride (table salt) is extremely unlikely to be an effective poison. My pessimism is because adult mosquitoes have salt-sensitive taste receptors just like we do and thus are rather unlikely to drink a solution that has such a high concentration of salt. I was unable to find a single published article that suggests mosquitoes would drink salty sugar solutions. Similarly, I couldn’t find any literature that said mosquito guts would rupture when forced to imbibe sugar/salt/yeast solutions. Indeed, when females take a blood meal they are, in effect, ingesting a high-sodium solution. They simply excrete the excess sodium in their urine.

Why, then, does the company use sodium chloride as the active ingredient, when even a quick internet search would reveal it is poor choice? The answer is a little complicated.

It turns out that the company initially used boric acid as a poison. I’ve uncovered two types of evidence for this. One is that “orthoboric acid” (not sodium chloride) is listed in the patent application. Another is a a video of the inventor/co-owner (Jeremy Hirsch) describing the poison as “boron or borax” to the Hattiesburg (Mississippi) City Council in April 2017; he doesn’t mention a salt version. I think he first settled on borax (which is cheap and easy to find) because he likely read, sometime in 2015 or 2016, an article in the New York Times titled, “Brewing up double-edged delicacies for mosquitoes“. In one part of the article there’s a description of an experiment that used boric acid to control malaria-transmitting mosquitoes in Africa. I think this was the article because Mr Hirsch often mentions in interviews that he thought he could improve upon what the Gates Foundation was doing (described more fully in Müller et al. 2010).

My guess is that at some point Mr Hirsch realized he wouldn’t be able to get EPA approval for the borax version so he switched to sodium chloride because it’s completely exempted from FIFRA (Federal Insecticide, Fungicide, and Rodenticide Act). Using table salt allowed him to sell it in almost every state without going through any type of testing. I.e., the Spartan Mosquito Eradicator can be sold even if it doesn’t work. I think Mr Hirsch was again inspired by that NYT article that described boric acid as “about as harmless to humans as table salt is.”

One odd part of the sodium chloride usage is how the company describes the mechanism of action: the mosquito gut “ruptures” in response to sharp crystals of sodium chloride. Even if you could fool a mosquito into ingesting a saline solution, this mode of action is improbable. Sodium chloride is ridiculously soluble in water so you’d need to have an extremely high concentration for salt to crystalize out of a solution. A 1% solution isn’t going to crystalize. I’m guessing the advertising was initially crafted to describe how boric acid kills insects and they decided to keep the wording. Boric acid acts in the gut, too, and some sites claim (without proof, I think) that it ruptures the gut.

As an aside, just in case an EPA regulator chances upon this post, listing sodium chloride as the active ingredient seems like a violation of the 25(b) exemption granted to this device. I.e., the sodium chloride is not actually killing any mosquitoes so it cannot be listed as an active ingredient. Moreover, Spartan Mosquito often says that mosquito’s guts are ruptured by the yeast’s CO2 emissions, not sodium chloride. As the inventor describes it (see video), “When they go in and they consume the material basically the material with the yeast and the sugar is constantly producing CO2 and mosquitoes have no ability to expel excess gas.”

Sodium chloride is the active ingredient.

Third, I don’t think the concoction is attracting mosquitoes. If it were, I would expect to see mosquitoes congregating around the device. I didn’t see a single mosquito, ever. As for reasons why the fermenting liquid isn’t attractive, it might be because the yeast runs out of sucrose in less than ten days (probably just two). Or, perhaps, the lack of attractiveness is because the odor profile is changed by rotting carcasses.

Why do people buy them?

Some people LOVE the Spartan Mosquito Eradicator. For example, more than half of the reviews on Amazon award it 5 stars.

Amazon ratings for the Spartan Mosquito Eradicator.
Most Amazon reviewers give either 1 or 5 star reviews.

What might cause so many people to give 5 stars? My hypothesis is that many of these happy reviewers live in an area that received aerial insecticide sprays soon after the devices were set up — many towns in the United States spray regularly in this way, and few people know that this happens. Other purchasers might just happen to have had low mosquito counts in their yards for some other reason (e.g., very little rain prior to setting the devices out in yard). Both of these scenarios can lead the average person to conclude that the devices they purchased caused the low mosquito numbers. I.e., they succumb to illusions of causality, a common mechanism that explains why people believe strongly in all sorts of strange things (dowsing rods, e.g.). Once a person decide the devices work the power of confirmation bias will continue to reinforce their conclusion. No amount of evidence to the contrary is likely to change their belief.

An additional reason to be suspicious of all the 5-star reviews on Amazon is that the pool of people who order miracle gizmos in the first place is probably not a random sample of people. That’s also true of people who see the devices in stores; skeptical folks might pass by the display and laugh but others will see the package and assume it works.

Another category of fan is the owners of stores that sell Spartan Mosquito Eradicators. These individuals get a percentage of sales so they are potentially biased, but in my experience speaking with them they seem 100% convinced that the claims on the package must be true (why would the company have mislead them!?). The proof, to them, is that people keep buying the devices (thousands, in some stores). My guess is that people who figure out that the devices are ineffective will just say to themselves, “Well, dang, I just wasted $19.95 but I’m not going to waste any time trying to return the darn thing. And I’m not going to bother the nice folks at the store that sold it to me. They’ll just trying sell me a fresh box.”

As a side note, I find it bizarre that the 5-star true believers keep buying replacement packs every 90 days. If these people are truly convinced that the devices work they could save a lot of money by just going to the pantry and refilling the tubes with fresh ingredients (I did the math: 2 1/2 tbsp sugar, 1 tsp salt, 1/8 tsp yeast, 1.7 cups warm water). The company is concerned about this scenario and has the following warning: “Spartan Mosquito Eradicators cannot be reused or refilled. Imagine a glass of orange juice sitting on your porch for 3 months. We don’t want people pouring tubes out on the ground and having a house pet consume the materials” (italics added).

Some 1-star reviews from Amazon

Some reading this review might think I’m biased in some way, so I thought I’d give you some snippets from several of the many negative reviews on Amazon.

“The container is a long skinny smooth tube. It has six tiny holes up on top. Supposedly, the mosquito will, somehow, detect the C02, fly up to the tip of the smooth plastic tube and squeeze itself in this 4mm hole, tucking its legs and body in as it slides itself in this pin hole. Then once inside, fly down the narrow shaft take a drink of water, fly up the thin shaft, and once again tuck its legs in and squeeze itself through to fly away. This concept is so far fetched. I would like to see real proof than unproven customer reviews. It would be great that the manufacture would show real data and show mosquito accessing these tubes as they say. I opened one up and poured the contents out. Only bugs I see are fruit flies and a few house flies, but not mosquito’s. I will take pictures next time. I find it interesting that the manufacturer mentions that the mosquitoes fly out, thus you will not see any mosquitoes trapped in the tube. Yet, fruit flies, and house flies, which are notoriously way better flyers and can crawl, can not find their wait out of the trap.” — bahhhoo (full review)

This product is a scam. The “active” ingredients are salt and sugar. You know, Malaria is a global problem. Don’t you think that if salt (aka sodium chloride) and sugar (aka sucrose) could actually reduce or eradicate mosquitoes, this product would win the inventor the Nobel Prize? The trap will collect some flies and bugs attracted to the sugar, but no mosquitoes. Also, if you write a “bad” review, the sellers contact you and tell you that you aren’t “installing” it correctly. You see, you have to put just the right number of traps in just the right locations in your yard. Yeah, right.” — Caveat Emptor (full review)

“I checked the traps several times over the course of the following months. Not only were the mosquitoes as bad as ever, the traps seemed EXCELLENT at trapping ants and gnats, but not a single mosquito that I could tell. I’d say don’t waste your money.” — Customer (full review)

These are useless. As another reviewer wrote, just look at the ingredients. I’ve noticed no change at all over the last few weeks these have been out. There are very few products that fit into the category of feeling like I was suckered for buying them and this is definitely one of those purchases.” — Tecsun (review)

A 5-star review on Amazon

This 5-star review is the most popular 5-star review for the product. The reviewer concluded that Spartan Mosquito Eradicators don’t work but gave them 5 stars because the company sent her some more. You really can’t make this stuff up.

My first review I gave one star because they did not work for me. I am now giving 5 stars for customer service. … I am going to hang as instructed and really hope they work. If they do I’m going to always have working sets hanging and encourage all my neighbors to do the same. I will update in a month with results. Very hopeful. Worth every penny if it will work.” — Tammy (full review)

Deceptive advertising

One reason so many people buy the devices is that they believe the marketing claims, probably because it seems sciency. Take, for example, the impressive graph that it uses to claim mosquito populations are all but eliminated in 90 days:

Graph of percentage mosquitoes eliminated over time by Spartan Mosquito Eradicators.
Graph of percentage mosquitoes eliminated over time. On its website this image is named, “Diagram-of-What_V3.jpg”.

A typical person is going to see this graph and assume that an actual experiment was done. Oddly, no details about this graph are ever given on the website or elsewhere (who collected the data?, where was it done?, when was it done?, how was it done?). I’ve talked to a lot of people about this graph and I think it shows the number of mosquitoes landing on Mr Hirsch’s arm on two different days during an event the company calls, “Case Study CSL4GOV-ZIKA”. Here’s a handout the company distributed (details below):

Spartan Mosquito Eradicator Case Study by Joseph Waits and MS State Etymologist
Photograph of handout describing a shady case study by Spartan Mosquito Eradicator staff.

The document says that a Lamar County official (Joseph Waits) and an etymologist [sic] from the Mississippi Department of Health conducted a study in late 2016. It is worded to imply that the Spartan Mosquito Eradicators deployed in the area eliminated 100% of mosquitoes and that the Mississippi State Department of Health participated and approved of the data. It turns out the reason the final mosquito count was zero was because the State of Mississippi completely nuked the neighborhood with insecticides (on multiple days). The State of Mississippi was focused on preventing the spread of Zika (from a single patient in the neighborhood) and had zero interest and involvement with the devices. The word on the street is that MS Department of Health is not pleased about how the document above was worded.

I’d also like to point out how the company ended the document: “To date, this is the most effective, longest-lasting Zika control response on record anywhere.” That’s a very bold claim. And appears to be a violation of the 25(b) exemption granted to the device. I.e., Spartan Mosquito implies the product can protect against a human disease. The claim is also made online: “Purchase the Spartan Mosquito Bomb and fight the Zika virus!”

“Purchase the Spartan Mosquito Bomb and fight the Zika virus!”

The company makes other bold claims, too. For example, it claims that the Spartan Mosquito Eradicator is better at controlling mosquitoes than pyrethroid spray services, automatic pyrethroid foggers, bug zappers, citronella candles/torches, and DEET repellents.

Finally, the company claims its devices are chemical-free. That’s not true (because NaCl, H2O, C12H22O11). Claiming a product is chemical free is also illegal.

It’s not just the company that spreads false, unsubstantiated health claims. Its affiliates and distributors do, too.

Here’s a typical post from the primary distributor, WDG Holdings, LLC. The implication is that you should buy a Spartan Mosquito Eradicator to protect yourself and family from eastern equine encephalitis. It is illegal to claim such protection when there is no credible scientific backing. Yet this distributor’s Facebook posts are almost exclusively claims such as this. These posts help explain why so many customers (feed stores, hardware stores) of the distributor make identical claims.

Facebook post by WDG Holdings, LLC telling people buy Spartan Mosquito Eradicators to protect against eastern equine encephalitis.

For example, here’s a commercial by Hub City West Farm and Garden that was broadcast on Mississippi television in early 2019. It claims Spartan Mosquito Eradicators can protect your family and pets from mosquito-borne diseases. Totally illegal. And because the claim could result in people not protecting themselves with DEET, also morally wrong.

I am almost certain there are scientists out there who have tested these devices and found that they don’t work at all. E.g., it wouldn’t take long to see that mosquitoes aren’t particularly interested in going through the holes in the cap. But anyone agreeing to test the devices for the company is prevented by a non-disclosure agreement (NDA) from discussing the results. Note to those scientists: you can break an NDA if you think the company is engaging in illegal activities (such as false advertising).

Distasteful advertising

In addition to misleading consumers, Spartan Mosquito also produced a video ad featuring a father hitting his kids. (The apron features a quote from Fox’s show, Bob’s Burgers: “A gentleman down south but a bad boy above the mouth.”)

Terrible customer support

The company has a carefully-crafted return policy: “Lights On Distributors [the distributor] does not honor returns due to improper use” (italics mine), and you have to return the product within 30 days. Per hundreds of interactions with 1-star reviewers on Amazon, the company always blames the user. Specifically, Mr Hirsch et al. will insist that the user failed to (1) “deploy” the devices early enough, (2) buy enough units for the size of the property, (3) place them in right spots, (4) place them at the right height in trees, or (5) wait long enough for devices to start working their magic. In some cases, all of the above. I fully understand that some devices don’t work if instructions are not followed, but I’d argue that this is not really one of them. The insistence that directions weren’t followed seems like a scheme to prevent people from returning the product and to immunize the company against scam complaints. Here’s a typical response (from Spartan Mosquito’s Facebook page):

If a buyer persists in claiming the devices simply don’t work, the company will ask the customer to call a “Deployment Specialist”, somebody who will call up your street address on a Google satellite map and tell you where you should put the devices (after you buy more). Sometimes the representative (Mr Hirsch himself, perhaps) will even inform the customers that it is really hard to educate the common person on the complex task of deploying the devices, all while referring to the customer as, “Sir” and “Ma’am” (which conveys politeness and annoyance at the same time). These tactics are not just patronizing, they are dishonest. Also, having a stranger examine your property on Google maps is creepy, especially if the interaction is done under duress. Given the name, “Deployment Specialist,” I’m assuming Mr Hirsch used to be in the Army.

By the way, if you do end up speaking with a deployment specialist and want a visual, here are photographs of the owners, Jeremy Hirsch and Chris Bonner.

Are “Sock-It Skeeters” any better?

Sock-It Skeeters are cheaper versions of the Spartan Mosquito Eradicator. The prototype is pictured below, followed by the version that is in stores now.

What can be done?

I didn’t just write this post to satisfy geeky people’s curiosity. I think this company should be stopped. Its products put people at risk of contracting mosquito-borne diseases, and this consequence will be especially horrifying if they are allowed to sell in countries where such diseases are orders of magnitude more common. So if you have made it this far in my long post, please consider helping me shut down Spartan Mosquito.

  • Share this post with your friends and neighbors so that they are not suckered. If you’d like to share something shorter, use this post, instead: “15 mosquito-control strategies and devices that don’t work“.
  • Leave a review on the Facebook page of either Spartan Mosquito Eradicator or Sock-It Skeeter. The Sock-It Skeeter also has a Shop page, too, and there’s a little button in the bottom right that says, “Report this product”. You can then select the “scam” option, if you want.
  • Leave a review at the Better Business Bureau.
  • File a complaint at Truth in Advertising. This organization allows the uploading of ads, so if you find an ad that you feel is misleading, include it.
  • Ask your state regulators to yank the company’s permission to sell. The company has to reapply every year (to every state) and these approvals are done rather automatically unless citizens highlight to regulators that Spartan Mosquito is violating FIFRA 25(b) rules. So just find your regulator (on this Excel spreadsheet) and email them, letting them know that company is violating laws. Send photographs of an ad if you can.
  • File a complaint with the Federal Trade Commission. Spartan Mosquito is exactly the kind of company the FTC goes after, but it will only do that if they get multiple complaints. Be one of them! To get you motivated, here are examples of other mosquito-related scam products that the FTC has investigated. The FTC has a really terrible form-based interface so I would recommend just calling them: 1-877-382-4357. Just describe how you think Spartan Mosquito is misleading consumers.
  • Contact your State Attorney General. One email isn’t going to move them but if they keep getting complaints about the folks at Spartan Mosquito, they’ll look into it.
  • If you’re a journalist, write an article. It would be really entertaining to explore how it came to pass that a company that was initially shut down for illegally selling a device with boric acid … became the fastest-growing company in Mississippi. And it would be fun to ask why the governor of Mississippi had to call the Bureau of Plant Industry to get the company out of trouble. Do the owners have some connection with the governor? Did lawyers for the Mississippi State Department of Health really serve papers to Spartan about the fake “Zika case study”? Is the company’s $16,000 donation of SWAT equipment to Lamar County some sort of kickback? Enquiring minds would love to know more!
  • If you have conducted research on the Spartan Mosquito Eradicator or the Sock-It Skeeter, tell the world about it. You might think that everyone else understands what a scam these devices are, but you’d be wrong. There are hundreds of thousands of people who fully accept the “carbon dioxide makes their guts rupture” explanation.
  • Start a class-action lawsuit. The company has been taking millions of dollars from hardworking people and it would be heartwarming to see the company give it all back. I’d like to see a big chunk of the settlement go to the Mosquito Illness Alliance.


Please email me if you have any information that might be useful.

Eliminate mosquitoes by eliminating stagnant water

The most effective, cheapest way to control mosquitoes is to eliminate the standing water that larvae need to develop. A dry yard doesn’t have mosquitoes. It’s really that simple. Below is a list of objects to get rid of or dump regularly. Please share with your neighbors.

1. Gutters

This is at the top of the list because almost all houses have gutters and almost all homeowners hate to clean them out. Check for blocked gutters weekly if you have a lot of trees nearby. If gutter status is hard to see, buy a drone to facilitate inspections. If you can’t afford a drone just get an extra-long, telescoping selfie stick for your smartphone.

2. Flexible downspout extenders

Flexible downspout extenders are perfect for mosquito larvae — the ridges hold water and trap organic matter, the black absorbs heat from sunlight (thus speeding development), and female mosquitoes of several species just adore ovipositing inside plastic objects. They are especially bad if nestled in shrubs and ground cover. Note that they hold water even if they are sloped downward. Get rid of them. All of them.

3. Tarps

If you leave a tarp in your yard, you’ve created lots of nooks in which water and debris will accumulate. I frequently see tarps covering soggy logs that owners seem to have no real intention of ever splitting into firewood. I think people view tarps as cloaks of invisibility, magically hiding loathsome to-do items from spouse.

4. Toys

Sandbox toys, sleds, wagons, and kiddie pools seem as if they were specifically designed to encourage mosquitoes. I.e., even when stored upside down they have nooks that collect enough rainwater to allow mosquito larvae to mature. Store them in the garage. If you think covering them with a tarp will work, please see #3.

5. Bird baths

Everyone should have a bird bath. But if you do, you need to either have a water bubbler/agitator (mosquitoes hate that) or you need to kill the larvae by adding granules of Bacillus thuringiensis var israelensis (abbreviated, Bti). Bti is extremely effective: you can add it a container that has thousands wriggling of larvae (see movie) and they will all be dead within hours. Just add it every two weeks and your bath will always be mosquito free. But don’t forget — make yourself a smartphone reminder or write on paper calendar.

Bird bath next to purple coneflowers

6. Trash and recycling bins

If you can’t store your trash and recycling containers under a roofed area, keep a lid on them. I found the ones below behind a local church. Tens of thousands of larvae within.

Recycling bins with stagnant water

7. Watering cans

Watering cans are rarely transparent so you can’t see the mosquito larvae inside, but they are present if you leave them around the yard when it’s been raining a lot. Store them empty, in garage.

8. Wheelbarrows

Just keep them propped up vertically so they don’t accumulate rain water. Or drill holes.

9. Rain barrels

Just put screening over the top. Or add Bti every other week. I don’t recommend adding mosquito-eating fish because they die when water level gets low (plus the fish suffer before dying).

10. Pot saucers

Pot saucers are unneeded outside so it’s easy to eliminate them. If you like them for decorative reasons you’ll need to add Bti regularly. It’s better to just get rid of them because you’ll eventually forget. You know you will.

Other places where mosquitoes larvae thrive

Below are photographs of stagnant water I’ve noticed around my town. On my list of photographs to add: bromeliad, pool cover, bottle cap.

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. 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:

All of the chemicals are pyrethroids, synthetic neurotoxins that cause almost instant paralysis and death to mosquitoes. Below is the chemical structure for one, permethrin:

Please email me if you think I’ve made an error or if you know that a formulation has changed (which happens). I still haven’t figured out whether companies permit their franchise owners to pick and choose which insecticides to use, so when multiple chemicals are listed above that doesn’t necessarily mean the sprays will contain both.

Are these chemicals safe for humans?

Pyrethroids are relatively safe but 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 adverse events. At very high doses pyrethroids can kill you, a fact known because some people have injected it and in one case because somebody ate food that was cooked in pyrethroid concentrate (it resembles cooking oil). 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. Each pyrethroid listed above has a slightly different toxicity, so to get more information Google the name or read the linked material by clicking on their name.

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 they can develop what is called pyrethroid toxicosis. A good indicator of cat sensitivity to pyrethroids is the standard warning of keeping them away from pyrethroid-treated dogs. I.e., if you dose your dog with a large amount of pyrethroids (to kill fleas, e.g.), friendly 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. But they are amazing pollinators and almost all adorable. 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. If you go out immediately after a spraying you can even see the twitching that precedes death (movie). It’s probably not a pleasant way to go.

Pyrethroids can kill ALL arthropods, in fact, not just insects. So if a yard is sprayed, likely 100% of spiders, mites, centipedes, and millipedes would be at risk. In total that could mean tens of thousands of individuals left twitching in treated yards. In one estimate, an acre of land in Pennsylvania contains 425 million animals … and a good portion of them would be killed by pyrethroids.

Another concern with gassing all the arthropods in a yard is that those 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 dramatically less aeration and dramatically more odor from rotting earthworm carcasses. And, perhaps, result in robins that wonder where all the worms have gone.

Pyrethoids are engineered to last for weeks

As mentioned above in reference to monarchs, pyrethroids adhere to plant surfaces and stay active for weeks, so the risk to all the organisms mentioned above also lasts for weeks. Here’s a nice (and hilarious) 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. One possible reason (in my view) that pyrethroids retain their ability to kill is that morning dew and guttation (see photographs) might re-suspend the pyrethroids on plant surfaces, and then insects walk through or drink these droplets (see photographs).

Signage and notification requirements

All of the above information is of course useful to those interested in getting their yard fogged, but it’s also important for neighbors of treated properties. The reason for this is because the aerosolized pesticide always drifts onto neighboring properties a bit (sometimes a lot). So if a neighbor has a patch of milkweed or a vegetable garden right along the property line, pyrethroids will kill monarchs and coat the vegetables. Homeowners should always check with neighbors before hiring a spraying service and should always personally inform neighbors when the spraying will actually take place.

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). In some states (e.g., Maine) you can get your name on a notification registry that requires any applicator to contact you in advance of spraying. 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). Also on this registry are beekeepers, apparently.

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 (I designed a template if your town needs one). In addition to maintaining the page, local governments should push prevention by sending to residents timely, regular reminders — with visuals — about how to prevent mosquitoes from breeding. Such tips might be especially important for towns that strive to be pollinator-friendly (e.g., Bee City USA, Pollinator Friendly Alliance, Mayors’ Monarch Pledge). 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. Or, at the very least, towns can remind residents that neighbors can (usually) ask franchises to provide alerts before the next spraying so that cats are inside. Finally, local governments should consider banning automatic pesticide foggers (pipes that deliver pyrethroids on a timer, just like those automatic misters in the grocery aisle).

Logo that says
Image from Mosquito Squad that was removed as soon as they read this blog post.

State governments can 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).  Some sites also use misleading graphics and logos (like the one on the right, from a Mosquito Squad site in Florida) to suggest that the EPA has approved the products on a page. I could be wrong, but I’m fairly sure that the EPA neither approves any of these chemicals nor provides that logo. But a typical homeowner might be fooled into thinking otherwise — that’s why state oversight is needed.

Is spraying effective?

Although spraying pyrethroids might be a good way to kill mosquitoes near the ground and in low shrubs, some 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. Continued spraying will also result in mosquitoes developing resistance to pyrethroids, something that is happening in Africa already.

But I don’t want to imply that spraying is 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. There are more genera of mosquitoes, of course, so depending on where you live and what is growing in your yard, pyrethroids might vary in effectiveness. I think most companies suggest that their sprays might miss 10% of the mosquitoes on a property (that leaves quite a few mosquitoes).

Prevention is cheaper and more effective

My suggestions for reducing mosquito numbers are: (1) get rid of English ivy if you have it, (2) get rid of stagnant water, and (3) deploy traps to kill pregnant females. And, of course, avoid techniques and scams that don’t work.

Further information

Please share this post with your friends and neighborhood groups. If you notice death of any type of animal after a spraying event, report the incident to the EPA.

If you have questions. please send me an email.