Tag Archives: insecticide

How to kill spotted lanternflies

Below are tips for homeowners who’d like to kill spotted lanternflies (Lycorma delicatula), invasive planthoppers from Asia that use piercing mouthparts to suck out phloem from a wide variety of trees, shrubs, and vines. It’s a futile endeavor to rid your yard of them, but you might be able to minimize damage to some of your prized plants.

First, kill your Ailanthus trees

The most important action you can take to limit population numbers in your yard is to make sure you aren’t harboring the spotted lanternfly’s favorite host plant, Ailanthus altissima (tree-of-heaven, ghetto palm), which is also from Asia and also invasive. Kill this plant with zeal and without regret, and leave no survivors. You should also locate any tree-of-heaven trees in your neighborhood and beg owners to kill them. Here are some photographs to give you a search image (click to enlarge):

To kill a tree-of-heaven you need to chop it down and then treat stump with herbicide (instructions). Alternatively, treat with herbicide (e.g., drill holes into trunk, squirt in herbicide such as glyphosate, tape over holes), wait until it dies (~1 month), then chop it down. If you skip the herbicide step you’ll just end up making it angry and you’ll have dozens of smaller trees in subsequent years. If you are horrified by herbicides this is the time to get over that.

Ways to kill nymphs and adults

Flyswatter: Nothing beats a flyswatter. If you are protecting just one tree, insert a pushpin into the trunk so that you have a convenient place to hang it. Make it part of your morning routine.

Rubber bands: These work like a charm and are mildly fun. Be careful of fragile leaves, though — rubber bands can cause more damage than the insects.

Lid-container technique: Fill a container with soapy water and use the lid to motivate them to leap inside. You can kill thousands this way once you get the hang of it.

Cordless stick vacuum: A long extension arm of a stick vacuum is ideal for reaching into vegetation. I own a Dyson cordless stick vacuum but there are lots of options (e.g., on Amazon).

Backpack vacuum: If you are serious about controlling spotted lanternflies, go buy yourself a battery-powered backpack vacuum that has a large, clear repository. Then you can stroll around your yard in the evening and suck up thousands over a short period of time. A shop-vac will also work in a pinch but is much less convenient because of the cord. PRO-TIP: buy a Ghostbusters costume for your gullible child and tell them sucking up lanternflies is good practice.

Leaf vacuum: Maybe something like the Black and Decker 36v Cordless (GWC3600L). I don’t own one of these but they look fun. Amazon carries a lot. Most hardware stores can set you up. Note that most leaf vacuums shred, so be prepared for some goo.

Circle traps: These involve a little time to make but they look fantastic. Here’s a page that gives detailed instructions.

Sticky tape: I strongly advise against the use of sticky tape and spreadable goo. Sticky surfaces will certainly kill some spotted lanternflies but in my experience, not that many. The real outcome is that thousands of other, smaller insects will get trapped, which in turn attracts other, larger insects keen on eating the trapped, squirming insects. Then insectivorous birds come and get trapped (click here if you doubt me), as will bats (click here if you doubt me). Many birds and bats will likely escape but will be covered with goo and may die later. If you are unconvinced that trapped birds and bats are a problem, I urge you to Google videos of such so that you can see them suffering. Those videos are just too horrible to link to. Also, tape can leave permanent marks on your trees.

Bug-A-Salt rifle: I don’t own one of these, sadly, so I can’t absolutely guarantee it will work. But I’d be really surprised if they didn’t. I think it would make the daily lanternfly patrol really fun, and everyone in the family would want a turn. You can buy them on the Bug-A-Salt website and on Amazon. Do not buy one if you have children in the house. You can definitely shoot your eye out with these things.

Airsoft gun: Don’t get one of these if you have kids. But if you have a semi-responsible adult who enjoys killing spotted lanternflies, this would be a sweet gift. I see them as especially valuable in killing the adults that are high up in branches, out of the range of your vacuum. Buy (1) only biodegradable pellets, (2) opt for lightest pellets you can find (to minimize tree damage), and (3) wear safety goggles (the pellets ricochet off tree trucks). Note that Airsoft guns are illegal in some areas (e.g., Arkansas, parts of Michigan, Washington D.C., San Francisco, Chicago, NYC). And, of course, you always run the risk of being shot by police even if you are on your own property. To minimize the risk of being shot, DO NOT remove the blaze-orange tip.

Electric flyswatter: I own one of these and they work really well on large flies so I don’t see why they wouldn’t work on spotted lanternfly nymphs. I suspect adults wouldn’t care. There are dozens for sale on Amazon.

Pathogenic fungi: There are at least two fungi (Beauveria bassiana and Batkoa major) that seem to infect spotted lanternfly, so it might be possible to coat them with a powder or a spray and watch them slowly die. Unfortunately, the experiments on whether this is worthwhile are not yet done (or not yet published), so I can’t guarantee success. But in the wild, these fungi seem to do their thing well. I’m going to buy some Beauveria bassiana from Amazon for the 2020 season, just for giggles. Batkoa major is not yet for sale, I think. Here’s an adult I found that I think is infected.

Dawn soap: This is one of many home remedies that has gone viral but should not have. Detergents pollute waterways and can also damage plants.

Propane torch: This looks extremely satisfying (see video) but it’s just going to result in forest fires and home losses. Don’t be that guy. If you’re married to that guy, hide the propane tank.

Chinese mantids: Please do not buy mantid egg cases and release in your yard. Chinese mantids are invasive and mainly eat butterflies (even monarchs, even hummingbirds). They are not beneficial insects, despite claims to the contrary on Pinterest.

Insecticides: Unless you own a vineyard, spotted lanternflies are a nuisance insect, not a health threat. And they do not seem to be killing trees or other plants. So I do not recommend spraying them with insecticides. A typical homeowner (I include myself) is not in a position to apply pesticides safely and in an environmentally-responsible way. You’d just end up killing all the pollinators and fireflies in your yard, plus pollute local streams. It’s also, in my opinion, futile to spray: there are likely thousands of individuals in neighboring yards that will reinvade your yard in the days after you nuke it. But if you do spray, please refer to Penn State’s guidance.

I also don’t recommend that homeowners treat male tree-of-heavens (Ailanthus altissima) with systemic insecticides to create “bait” trees. It seems like a perfect solution: because tree of-heaven is their favorite host, you could potentially kill thousands of adults as they arrive to feed on insecticide-laced trees. And it’s touted as being safe for other insects because few other insects eat the foliage. The huge downside, in my opinion, is that many systemic insecticides find their way into nectar and pollen, and thus these bait trees will likely poison large number of pollinators (you’d just never know it). This downside should be especially worrying to suburban beekeepers because those chemicals could potentially end up in honey. And, more generally, the bulk of systemic insecticides is likely washed into waterways or taken up by nearby plants in your yard, not just tree-of-heaven trees.

Ways to kill eggs

There are several challenges to killing them at the egg stage. The first is that the egg masses are covered with a shiny purple/gray substance that tends to weather and blend in with tree bark over time, so finding them is difficult. Here are some photographs that illustrate the variability (click to expand).

The easiest way to kill large numbers of these insects is to find them at the egg stage and squish them. This can be done by applying enough force with a hard, flat object (stick, trowel, stiff credit card) to create a popping noise as you progress from one side of the case to the other. You should see juices being exuded.

I also think that a mini rolling pin would be ideal, as would a rubber mallet.

PRO-TIP: In late winter and early spring the egg masses becomes brittle, so apply a section of wide tape over the egg case before hitting them. This prevents eggs on the edges from being launched to safety.

If you can’t stomach the sound and the goo, an alternative is to scrape the eggs into a container filled with a fluid such as alcohol or hand sanitizer, or into a container or bag that can be sealed and thrown in the trash. The important consideration here is that simply scraping them off the tree onto the ground will not kill the eggs/larvae that are inside.

Second, the egg masses are often high up in the canopy of a tree, sometimes on thin branches that you’d never be able to reach even if you are a good climber. Third, the adults have a habit of ovipositing in areas that are completely hidden from view, such as underneath a loose piece of bark, behind a seat cushion on the deck, or in a wheel well of a car. There’s just no way to find all the egg cases in a yard.

PRO-TIP: as the egg cases weather the eggs beneath the waxy substance sometimes become more visible. So make a habit of reexamining surfaces in February and March when leaves are not blocking your view. Take a cup of coffee or a glass of wine with you on patrols, to keep your spirits up. As motivation, remember that each egg case has 20-50 eggs, and they are much easier to kill than 20-50 nymphs.

As far as I know, spraying the egg cases with insecticide is not especially effective.

More information


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.

Do pyrethroids affect plants?

As you might expect, plants that depend on pollinators are likely to have reduced seed production if dosed with an insecticide. E.g., Brittany Harris found reduced reproductive success of rare plants in Florida when they were located near houses sprayed with insecticide. Pyrethroids can also harm plants directly (e.g., Tu 1981, Bragança et al. 2018).

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.

Complimentary fumigation during flight to Galápagos Islands

Before arriving in the Galápagos Islands, you get to watch the cabin being fumigated with insecticide. Because the plane is full of Prius owners who listen to NPR, it was fun to watch peoples’ faces as they slowly realized what’s going on. The audio couldn’t pick up everyone’s conversations, but trust me, it was funny. They don’t ask, “Would anyone mind if we sprayed a little insectide right now?” They just start doing it.

I think the prior to the spraying the captain should have cued up a short video on what introduced insects can do to the islands. For example, showing the devastation of Philornis downsi. Then again, people might be eating …

By the way, when you step off the tarmac after the flight you walk over a spongy mat that has even more chemicals, suspended in a soapy liquid, to kill the things that might be hiding in your treads. Pro tip: watch your step after coming off the sponge mat … it’s incredibly slippery, and will make you wonder whether the airport planners have a firm grasp of basic safety protocols.