Aerial spraying and honey bees

Have your colonies ever been hit with aerial mosquito spraying? Unfortunately, it’s a common experience. Today’s featured question is about a specific insecticide, naled.

More than half of my bees died from an aerial spray with naled. They sprayed between 6 pm and 8 pm in the evening when the bees were already inside the hive, and there was enough poison 12 hours later, that several thousand bees died in the morning. Today, 5 days after the spraying, the bees are not able to fly and fall to the ground dying. However, this is what EPA has on their webpage for naled mosquito control:

7. Is naled harmful to wildlife?

“Risks to wildlife from aerial application of naled for mosquito control are minimal because naled is applied from several hundred feet above the ground, at low rates, and it does not persist in the environment. However, because naled is an insecticide, invertebrates such as insects, crustaceans, and spiders could be affected. In addition, wildlife present in the immediate treatment area could be affected shortly after spraying occurs but long-term effects are not expected.”

8. How can a beekeeper reduce the risk of bee exposure to naled?

“Spraying naled can kill bees that are outside of their hives at the time of spraying. However, spraying typically occurs between dusk and dawn (when mosquitoes are most active), which is when bees are usually inside their hives. Although EPA does not anticipate that bees will have significant exposure to naled due to the timing of most spray operations, beekeepers can further reduce potential exposure by covering colonies when spraying takes place, or if possible, relocating colonies to a site that will not be sprayed. Providing clean sources of food (supplemental sugar water and protein diets) and clean drinking water to honey bee colonies during application can further reduce exposure.”

Obviously, these studies were not done with real bees or they would have seen that the results are devastating to bees. In my case, naled persisted in the environment for 12 hours and that is how my bees were poisoned the following morning.


Words of wisdom

When it comes to pesticides, it helps to take a lesson from the X-Files: Trust no one.

When you get down to basics, you’ll find that naled is an organophosphate, a type of chemical that is highly toxic to bees. So my first recommendation is to research the chemical family, not just the common name.

Or you can try going to The National Pesticide Information Center. Regarding naled, it says, “Naled is also highly toxic to bees through direct contact (LD50 of 0.48 micrograms/bee). Indirect contact with plants was found to be highly toxic one hour after application and practically non-toxic one day after application. During a field application, naled was low to moderate in toxicity to honeybees after three hours.”

Aerial spraying in real life

It’s easy to forget that conditions during field trials can be very different from real-life conditions. In your case, the person who mixed the chemical could have made an error. The spray tank could have contained a chemical residue from a previous job. The pilot may have flown lower than he should, or he may have repeated an area. Wind conditions may not have been optimal. Any number of things could have caused a bad result. 

Bearing in mind everything that could go wrong, I always go to great lengths to protect my bees. Although we don’t have mosquitoes in my area, the Department of Natural Resources occasionally administers ground spray for certain things, usually weeds. But even then, I keep my bees locked up for a day or two to keep them safe.

If it’s hot, you will need to provide ventilation and a water supply, and if it’s really hot, you may need to provide shade as well. 

Pesticides harm living things

Remember that insecticides are designed to kill insects, so honey bees are easy targets. But a poison designed to kill any living thing, including plants, fungus, or molds, can affect your bees. We can’t possibly know all the ramifications, so I think it’s a good idea to do everything you can to protect your colonies. And trust no one.

Honey Bee Suite

Spraying conditions are not always ideal, so variations in coverage can happen.
Aerial spraying conditions are not always ideal, so variations in coverage can happen.


  • Please check with your county mosquito control, we register with ours and they gps our location by physically coming to our hives, we do not get sprayed. See what your state and county do in this regard.
    Location: Florida Pinellas County

  • In late September of 2019, spraying was done in Michigan due to EEE (Eastern equine encephalitis) outbreaks. The state used Merus, a pyrethroid. I am located just a little bit outside the spray zone, I had submitted my location as a “no-spray” area. (2020 in Michigan, no-spray zones were not acknowledged). All seemed to be ok. I had covered my three hives with wet sheets for the nights of the sprays but did not keep them locked inside for a few days as some experts recommended. Fall progressed, I did my VOA treatments and buttoned them up for the winter. In the spring, Hive 1 totally empty. They had absconded very late in the season. Hive 2 dead with an ungodly amount of queen cells. Hive 3 re-queened itself but it was to be expected due to being a captured swarm from the spring of 2019. No spraying in my area of the state in 2020. This colony did fine over the summer and is now tucked in for the winter. Just weird…….

  • I lost a colony of bees due to spraying for mosquitoes, and the effect was immediate. They were dead in a couple of hours. The other colonies were unaffected and I think it was bc of location. Since then I have moved all hives in, but there was no mosquito spraying this year either. However, my colonies are exposed to ag. sprays on a regular basis. It would seem the benefit of any spray is for somebody’s bottom line. This short term gain is not worth the long term costs. The way we live is unsustainable. Maybe we will learn how to live within the confines of Mother Nature’s rules before she has her way with us.

  • Trust No One. If you have to Trust, Trust your Dog! This happened at our place one year. Not the same chemical, but aerial spraying. I was in the woods training the dogs when the plane flew over and we got sprayed in the middle of the woods! I had to run the dog’s home, bathe them and myself, etc. Whatever it was just splotted on us in huge splots.

    When I tried to find out who was spraying fields in the middle of the day, I had no success. The State of Ohio was useless as was most Farmer’s Exchanges, Aerial Flyers, etc. No one would take responsibility or let me know about the business that was spraying. As days went on and I got ‘madder and madder’, I decided to take on the farmers around me and go house to house to tell them the destruction they did by spraying in the middle of the day. Not only to my bees, pollinators, birds, etc. but to me and the dogs who were out in the woods training.

    Since then, I have no patience for this stuff. Not around my place. If you want to be a farmer, be a responsible farmer. Also, be a responsible neighbor to the wildlife around you. Protect them from these people who tend to do as they want and kill off what they want. I feel bad for the person who lost their bees, but as a beekeeper, I have learned that nothing is sacred especially bees. You tend to lose them to pesticides no matter how careful you are. They just can’t get away from chemicals that kill them. Kinda like people nowadays!

    Great article Rusty. Hit home.

  • I am so sorry for everyone’s honey bee losses, but my heart is breaking for all the invertebrates whose keepers were not protecting them from these insecticides. Luna moths, firelies, lacewings, native bees, dragonflies…the list is endless and so sad to me.

  • How the heck do you keep the bees locked up for a couple of days? Or even one day? I don’t think anyone really cares about honey bees in Utah. I found out the only beekeeper that I know of near me ( I know he has bees because I see his hives). When I went to ask about how his mite loads were and how he was treating them he told me he does not treat them, he strips the hives in the fall and kills the bees. Then every spring he just gets new bees. When I tried to see if there was a way to stop this, I effectively got told to mind my own business. I cannot really find out much of a helpful nature from anyone. It is my first year, and I am finding most of my information from YouTube and websites like yours. Thanks for that anyway.

    • Kathleen,

      It’s quite easy to lock up your bees, which is what migratory beekeepers do when they need to move them from place to place. You wait until evening or early morning when the bees are home, and then you close the entrances. If they will be in a hot place, you will need to provide water and ventilation.

      Killing colonies and repurchasing new ones in spring is still quite common, especially in colder areas where it is difficult to overwinter them. Like you, I don’t agree with it, but it’s an established practice that is probably not going away any time soon.

      Many caring and dedicated beekeepers live in Utah; you just haven’t found them yet.

    • Kathleen Cutler – Not sure where in Utah you live and keep bees. I live in Kaysville and have hives in West Kaysville as well as the East Bench in Bountiful (near the Temple). I have kept at least 4 or 5 hives for the past decade. The Davis County mosquito abatement talks a good talk and noted to avoid my property – however, the kids driving the truck either didn’t get the memo or didn’t care. They’ve nuked a few of my nucs over the years. I have to lock them up one night a week when they treat for mosquitoes. I let them out the next afternoon, and although grumpy – they get over it quickly.

      If you’re looking for a local resource, there are a few local associations. Check out Richard Homer’s website for dates when we meet to discuss what’s going on locally with our hives. Many of us have kept bees for many years, have local nucs with local queens, and would never consider killing our hives (they can winter just fine here).

      Good luck with your new hobby. Hope to meet you at a club meeting – virtually for now.

  • Rusty —

    I’ve been lucky to (so far) have no serious difficulties with pesticides (didn’t see any spraying this year, though I’m sure it was happening). And I gladly don’t live in traditional bear country, so many of the blink-and-miss-it / catastrophic problems weren’t an issue.

    What I DID have a problem with this year was vandals. Which I did not see coming. Previous beekeeping years I lived out and far enough away that passerby’s would be near impossible. This year in a new part of the state, I’m in a more human-habitated area. The hive in question is still a good walking distance away from other properties (closest property is 1/5 of a mile away as the crow flies) and the hive is tucked away where I was pretty confident that it wouldn’t be visible unless you were right on top of it. (Assumptions, but a lot of time was spent in choosing the location!)

    I had visited the hive just to observe from the outside on the 11th and then returning on the 19th for another check, I found the hive had been knocked to the ground. Two deeps and a medium super, towards the end of summer, so quite heavy with brood, honey, etc. I was really baffled (after the shock and dismay wore off a bit). We hadn’t had any storms or any wind at all. I searched for animal signs and tracks. Nothing. I looked for fallen tree limbs or something that may have hit it, even though there are no overhead trees. Nothing.

    Eventually, I had to draw the conclusion that the wreckage was human-caused. The biggest proof was lack of other causes (like wind storms), lack of immense damage (the frames weren’t torn apart or open like I might have expected from raccoons?). But the biggest red flag for me was finding a very large stick that couldn’t have come from any of the nearby small trees and shrubs, and parts of a nearby empty hive which were among the wreckage and couldn’t have moved there on there own.

    What it looked like to me was the large stick had been used to tip the hive over from a distance, and the parts of the empty hive (outer cover, large rock weight, empty super) had been thrown at it to also try to knock it over without getting too close.

    Luckily, there was minimal damage, I was able to put the hive back together, and it survived the rest of the summer and is now working on making it through winter. (My last proof it couldn’t have been wind even if I somehow missed a freak gust, is we just had a huge blizzard with 60+ mph gusts. The hive didn’t even budge.)
    In response to this incident, I did put out a remote trail camera but never caught anything more sinister than a visiting rabbit.

    My question is — have you heard of other keepers having this problem? Are there preventative measures that work best that others use? I could strap them down, put up signs, etc., just wondering what might be the best protection? (Other than 50,000 stinging insects)

    • Stephanie,

      I’m sorry to hear about your experience, but vandalism is extremely common. What you describe here sounds like the teenage-boy type. Read my prior post on vandalism for some ideas to help reduce it. There are more ideas in the comments section, too.

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