Are your chickens suffering from mite infestations? Roost mites (also called red mites, nest mites, chicken mites, or even dermanyssus gallinae) are a problem that can happen to any flock, especially a free-range flock, since the mites are spread by wild birds. If left unchecked, they can cause a lot of suffering.
Because the mites are so tiny and have such a high reproductive rate, they’re hard to notice until things are getting out of hand. Knowing what to look for and what to do will make control a lot easier.
Does Your Flock Have Roost Mites?
How can you tell if your chickens have a mite infestation? Some indicators:
If you pull out a handful of nesting material, it exposes a mass of little reddish moving thing, you have roost mites. Ditto for when you lift a roost and look at its underside. (Roost mites mostly hide during the day, preferring dark little cracks and crevices.)
- If you have a crawly sensation in your arms or legs after visiting the chicken coop, you have roost mites. Eww! (They only mostly hide during the day. When a potential victim comes near, they jump aboard.)
- If some eggs have reddish-brown spots or smears, you probably have roost mites. Though some eggs have reddish-brown speckles naturally. (Mites drink blood from chickens and swell up like balloons, then wander off. If they happen to be in the wrong place at the wrong time, they’ll be squashed by a newly laid egg, and the stolen blood marks the eggshell.)
Do You Have to Treat Roost Mites?
Yes. They are sometimes enough to kill chickens outright, and can easily cause pain and suffering.
Treating Roost Mites
Since this is the Internet, there’s a lot of bogus information about treatment, reflecting a variety of fads and superstitions. (When in doubt, look at research summaries, which in the US can be done with good results by adding “edu” to the search string.)
Remember, health fads rely on the miracle of the placebo effect, which guarantees that almost any kind of quackery works to some degree on humans. (In areas where our treatments don’t work very well, the placebo effect is often stronger than the therapeutic effect.) Sadly, chickens aren’t sophisticated enough to benefit from placebos, so you should treat chickens with workaday practicality.
All effective treatments reduce the mite population to near-zero, and some keep it there for a long time. Many methods that kill adult mites have no effect on their eggs, and these methods need to be repeated more often.
Ways of eliminating roost mites:
- Heat. Heat will kill both mites and eggs. Milo Hastings recommended boiling water in his 1909 book, The Dollar Hen (which I have republished under my Norton Creek Press label). Given the limitations of the tools available on a 1909 farm, he specified using a dipper to fling boiling water from a pot onto the infested areas. A hot-water pressure washer would be a fancier modern method.
- Smothering with oil. Mites breathe through microscopic pores, and suffocate if covered with a film of oil. This also kills their eggs. For decades, the traditional mite-control method of US poultrymen was to paint wooden roosts and nest boxes with used motor oil thinned with kerosene. You can get the same effect with linseed oil thinned with turpentine, which smells better and doesn’t contain any funny chemicals. The surface of the wood will become dry almost at once, but the cracks and crevices that harbor the mites remain oily enough to continue killing them for months.
- Laceration. Wood ashes and diatomaceous earth in a dust bath can lacerate mites to death. Of course, the roost mites don’t actually live on the hens, so this is a bit indirect, and it has no effect on the eggs. In my experience, wood ashes and diatomaceous earth place in the nest boxes are also ineffective. I expect these methods may prevent some outbreaks, but aren’t strong enough to stop them once they’re established.
- Poisoning. Just about any insecticide works on chicken mites. My personal preference is for insecticides that (a) are much more toxic to mites than birds or mammals, (b) have low persistence, so they’ve broken down into something harmless long before next season, (c) have a zero withdrawal time, so I don’t have to throw out, say, a week’s worth of eggs after treatment, and (d) are inexpensive. I typically have to use insectides 2-3 times per year, compared to oil, which I use once or twice. Probably this is due to mite eggs being more pesticide-resistant. Some candidate pesticides are:
- Permethrin. Basically a synthetic pyrethrin insecticide, permethrin has a longer half-life than I find ideal, but I can actually find it in local stores, and that’s something. I’ve used permethrin in dust form with good success.
- Lime-sulfur. This is a traditional miticide. It smells like rotten eggs, but is pretty effective and it main environmental effect is that it’s a pretty good fertilizer. I’ve used lime-sulfur spay. Powdered lime-sulfur is also supposed to be good, but I haven’t tried it.
- Pyrethrin. A natural insecticide made from flowers, I’ve found this very effective in mite control. For some reason it’s getting hard to find in my area. I mostly use pyrethrin dust in a one-pound shaker can.
- Malathion. Malathion is a synthetic insecticide that resembles pyrethrin in its low persistence, low toxicity to birds and mammals, and general means of use. It’s very inexpensive. The brands available locally aren’t labeled for use on poultry anymore, for some reason. I’ve had good success with both malathion dust and malathion spray.
What results have you obtained with mites? Leave a comment below!