Tag Archives: safety

Bti honeypot traps for killing mosquito larvae

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An easy way to kill thousands of mosquitoes each summer is to drop some Bacillus thuringiensis israelensis (abbreviated to “Bti”) into containers filled with stagnant water. The photograph below shows one fashioned out of a litter box, but any large container will work. Then just lob in a Mosquito Dunk (made by Summit) or any equivalent product that contains live Bti spores, and repeat every three weeks so that there is a fresh supply of bacteria. Over the summer months, hundreds or thousands of females will find the container and oviposit onto the water surface as well as any objects such as wood and terracotta pots placed inside. When the larvae begin to feed they’ll be killed by the toxins produced by the bacteria.

Tips

As you can see from the photograph, I’ve covered the container with chicken wire. This prevents birds from drowning but also serves to prevent dogs, foxes, deer, and raccoons from draining the water, which they do quickly in my yard.

To increase the attractiveness of the water, add a handful of leaves or grass, which decompose but emit distinctive volatiles (not CO2, fyi) that attract gravid females.

I’ve also added a board that is partially submerged so that Asian tiger mosquitoes have something wet and rough to oviposit onto (they don’t oviposit onto the water’s surface like many other species). I set the board at an angle so innocent insects might be able to climb up out of the water when they fall in. Terracotta pots are another excellent option because the entire surface stays hydrated, something that mosquitoes love. Even some dry leaves floating on the surface will do the trick.

Finally, I recommend adding some sort of white object (like a yoghurt lid weighted down with a rock) that allows you to easily view larvae wriggling around; if you see them you need to add a fresh Mosquito Dunk or equivalent.

When siting your honeypots (the more the better) opt for locations that don’t get direct sunlight, are near vegetation, and are at the bases of larger trees. And it’s totally OK and even preferable to have each of your honeypots set up in a different way. E.g., if you live in an area with yellow-fever mosquitoes (Aedes aegypti), add some salt (0.25%) to increase oviposition rates. And other species of mosquitoes like large amounts of rotting vegetation. Your yard has dozens of different mosquito species so the trick is to identify your problem species and then design a honeypot that attracts them best.

PRO-TIP: If you don’t mind eye-sores in your yard, use tires. Asian tiger mosquitoes go bonkers for them. For slightly prettier traps you can cut tires apart and make ovillantas (“egg tires”). Smithsonian Magazine has a nice overview of these traps (just swap in Bti instead of the pesticide). You’ll need a Sawzall-type tool to cut through tires with metal reinforcements.

Purge your yard of standing water

Bti honeypot traps won’t do a thing if mosquitoes have plenty of other sites where they can dump their eggs. So get rid of all the objects that are accumulating water: kid toys, plastic tarps, saucers under plant pots, etc. And make especially sure that your gutters are free of clogs. If you’d like a visual guide to the places that accumulate water, see this page. The success of Bti honeypot traps will also be improved if you can somehow get your neighbors invested in removing their stagnant water, too. One trick for getting neighbors on board is to make sure one of yours is highly visible when you have people over for dinner. When they ask what that is, have one ready to gift them. The more neighbors participating, the better.

Are they working?

To determine whether mosquitoes are ovipositing, just look for egg rafts on the surface of the water. Eggs from Asian tiger mosquitoes (Aedes albopictus) are oviposited singly or in small groupings on the edges of the container or on pieces of wood. If there are eggs and no larvae, the Bti is doing its thing.

Raft of mosquito eggs (Culex sp.) next to a dead female mosquito.

Warning

After a few weeks the bacteria will die off, so you have to keep adding new Bti throughout the summer, approximately every three weeks. But as mentioned above I think it is a good habit to glance at your containers every several days to confirm that the Bti is doing its thing. If you are not vigilant about refreshing the Bti all those containers will start pumping thousands of mosquitoes into your yard every week and your neighbors with loathe you if they don’t already. So if you like to start projects but not maintain them, Bti honeypots are not for you. Here’s what mosquito larvae look like:

Are they safe?

Bti toxins are completely nontoxic to mammals, birds, and all insects except mosquitoes, black flies, and fungus gnats. For an excellent overview of the mode of action and safety, please see this report (PDF).

Sources of Bti

Other sites with similar information

Killing adult mosquitoes

If you also want to kill adult mosquitoes, please see my post on autocidal gravid ovitraps. Several companies sell them but you can make your own. I own a half-dozen of these traps AND a similar number of Bti honeytraps.

Autocidal gravid ovitraps made by Biogents and Springstar.

How to protect yourself from ticks

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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.