Grain Mites in Horse Feed

Have you ever had the following situation happen to you? You go out to feed your horse and notice a fine dust on the outside of the feed bag. You look closer and realize the dust is moving! Yes, you can see all those little bugs bustling about, in search of food and other little bugs to reproduce with. Yuck! Where do they come from? Is the feed safe to give to your horse? Can they harm you?

Magnified image of grain mites

It turns out that these little critters are grain mites (Acarus siro L). Grain mites are common and exist in all grains, but only thrive and appear when the conditions – temperature and humidity – are just right for reproduction and growth. Their ideal environment is warmer than 77 degrees F, and over 85% humidity. Hence, you would have more problems with them in the warmer months of the year. Temperature changes, condensation, and poor ventilation may produce areas with enough moisture to encourage mite infestation.

If you have infested feed you should not feed it to your horse. These mites can contaminate the feed with allergens and can also transfer nasty germs. Infestation can negatively affect palatability and when animals are fed infested products the results can be decreased intake, inflammation of the intestines, diarrhea, impaired growth and allergic reactions. The good news for you personally is that these mites do not bite humans.

To help reduce your incidence of mite outbreaks:

  • Store your feed in a cool, dry place
  • Use your oldest feed first
  • Keep no more than a two week supply of feed on hand (especially in hot weather) to ensure freshness
  • If you store your feed in a container, clean it regularly between fillings to prevent buildup of fines
  • Keep your feed area clean and neat
  • Air movement, such as from a fan, can help prevent outbreaks

If you do have an outbreak in your feed room, remove affected feed from the room immediately and thoroughly clean the area. Pyrethrin can be applied to the area with a hand held fogging machine or aerosol spray can.

40 Replies to “Grain Mites in Horse Feed”

  1. The best feed bin I have used is an old (but not rusty) chest freezer. I find them at used appliance stores . I cut the broken compressor out of them so it is not so heavey. They are insulated and have a sealed lid which stays open while you scoop out your feed and closes easily. My feed stays cool in the summer and does not get hard (sweet feeds) in winter. Bugs and mice stay out and my feedroom floor stays cleaner. A fifteen cubic foot chest freezer will hold ten bags of feed and a seven cubic ft. Chest holds four bags of feed. I also like to divide them into two or three sections using strips of trim and 1/4inch finished plywood (no splintrrs). The interior is smooth and easy to clean. I use a square plastic scoop to get the last pieces of feed out in each section before I pour fresh feed in.

  2. I have an abundance of squash from my garden, and was wondering if I could give some to my horses?

    1. Hello Vicki,

      Interesting question! There is some information available about feeding squash to horses. Appears that there is nothing toxic about squash, pumpkins or melons as long as they are introduced gradually and fed in moderation. Also must not be fermented or moldy.

      Like any feed, best not to introduce too much at one time or overfeed. You may also want to consider getting the squash analyzed for nutrient content if you are introducing it as a major dietary component to ensure that your horse’s diet is balanced. If it is used as a low volume treat, analysis is less important.

      There is some indication that raw potatoes & vines are not recommended. Also, cruciferous vegetables are not recommended. Do not get your horse hooked on broccoli, kale, Brussels sprouts etc.

      Roy J.

  3. I might have grain mites…. My feed bags are very dusty looking and it is very dusty by the seams of the bags as well. What should I do with those bags? I do get rid of grain mites?


    1. Hi Stacey,
      Great question! First, I would make sure that what you are seeing is, in fact, grain mites. If you watch the dust closely do the particles move? If it’s mites you should be able to see them crawling around. You may want to grab a magnifying glass and check to make sure that it is mites and not just dust. If you do find that these are mites we recommend that you do not feed it to your horses for the reason listed in the article, including digestive upset and allergic reactions. Instead, dispose of the feed and clean your feed storage area completely by sweeping up any stray feed particles, and cleaning every nook and cranny that the bugs could reside in. You may also want to spray the area with a bleach/water mixture. Start over with a fresh bag of feed and keep a limited supply on hand to help stop infestations of mites – usually a two week supply is recommended, especially in hot and humid conditions.
      Hope this helps!

  4. I was given bad advice and fed my horse some Stud 14% with grain mite in. What do I do now?

    1. Hi Madeleine, thank you for reaching out. If you’ve already fed the feed, then all you can do at this point is keep an eye on his health and behavior. If you see anything unusual, contact your vet immediately.
      Thank you ~ Gina T.

  5. Our daughter had her horse feed in the garage.
    during the December holiday we have noticed mites in the living area. It is a small hard little bugger. At first we thought it was fleas, but I tried to squeeze the little thing and it was so hard that I had to really press down hard.
    Can I presume that it is mites? Now they are in the house.
    We have cleaned the area, but I presume not to good as they will hide in cracks etcetera.

    How do we get rid of them? Is it a hazardous thing? Will these mites go into our clothes, cupboards etcetera. Please help as I am at my wits end.

    Thank you

    1. Hello Marlize, Thank you for contacting us. Mites are generally harmless to people, pets, furniture, etc – they are simply annoying. Wherever they are, you can apply Pyrethrin spray with a hand held fogging machine or aerosol spray can. You may want to check with a local pest company for assistance or further guidance, particularly if they are in your kitchen area.
      Thank you ~ Gina T.

  6. It sounds like Marlize van Zyl may have something other than mites, they may want to check with a Pest Control specialist. If it looks similar to a flea it could possibly be bedbugs!

    1. Sounds like Weevils actually. Sadly what I’m dealing with. I had the 20 bags of Rice Bran fogged and all of the weevils died. I am now finishing up the bags with the dead weevils since I shipped them all the way from Germany. Problem is, she has skin issues like crazy (recent). I am now thinking this may be connected…. Is this possible ?could the load be too much for her system and cause what looks like Sweet Itch?

  7. I found little white worms in the feed didn’t notice till I feed him he has been wormed bit will that little hurt him

    1. Hi Richard, While it’s unlikely that a single instance will do much, we recommend keeping an eye on your horse for 24-72 hours after the feeding, and if he displays any unusual symptoms, contact your vet immediately.
      Thank you ~ Gina

  8. Hello, I just bought a few bags of feed from my local feed store, after only 2 days of being at my house, I opened the bag to pour into my container and noticed a few clumps of moldy feed….there wasn’t too many clumps, but I don’t know how many is too many…is this ok to feed to my horse if I remove the clumps before feeding? Also, there is what appears to be a date on the bottom of the bag, and I think I’m reading 5 June 09 does that mean this feed was made in 2009 and is that old? how old is old? thanks!

    1. Hello MC, Thanks for the question! When in doubt, don’t feed it! And in the case of mold, we would definitely recommend not feeding it. It would be better for your horse to simple go without grain and only eat hay for a day or two if you can’t get right back to the store for fresh feed, than to possibly consume moldy feed.

      As for the date on the bag, that is more likely from June 9th of 2015 than the other way around, but if you are unsure, ask your feed store to help you interpret the date to be sure. As for how long it is good for, feed does have a definite shelf life – it’s perishable just like milk or bread from the grocery store. Pelleted feeds last a little longer than sweet feeds since they are lower in moisture and thus less likely to mold, but we typically recommend using any feed within 3-4 months at most of the manufacture date. Vitamins and amino acids will start to break down after about 6 months. Ideally though, for optimum freshness and palatability, you would want to feed a product within 30 to 60 days, though.

      Hope that helps! Thank you ~ Gina T.

  9. I got mites in my feed all my feed. Chicken. Potbelly pigs.. Horse.. Cat..and Rhea feed I use metal cans to hold my feed someone told me to just spray the lids and inside of cans with horse fly spray and will kill them and its ok to feed to all animals. What u think

    1. Hello Cheryl,

      You will need to clean and wash out the feed bins, and then a spray that is a Pyrethrin spray is what will kill mites. Check at your local feed or farm store, and they should be able to point you in the right direction.

      Thank you ~ Gina T

  10. Hi iv just come across these horrid little mites all over my feed bags, iv cleared the room out of all 6 bags of feed and we are just cleaning the room now with vinegar /water. Do you know how I stand with getting my money back as there are 6 bags wasted ????Thanks Helen

    1. Hello Helen,
      Thanks for the comment. We always encourage you to visit with your feed store, as they also likely are dealing with the mites. If you are able to return the feed, or work with them to get refunded, we at Nutrena will always take care of the retailer from our end. If your retailer is unwilling to work with you, and the product in question is a Nutrena product, you can contact us via our website, and we will work with you to help you out!
      Thank you ~ Gina T.

  11. Hi Gina, Tiffany, and company. The photo in this article is not of grain mites. It is psocids, also known as booklice. Psocids are very tiny insects – although not as small as grain mites – and can be recognized by a large “buck tooth” on the front of their head. The pests in the photo also have an insect type body shape, not a mite body shape. The rest of the information you give is great. I still wouldn’t feed psocid infested feed to a horse, and psocids do like the higher humidity. First in, first out, sanitation, and proper storage go a long way to keeping our food pest-free.

    1. Hello, May I ask, do you think a horse could be susceptible to parasite overload from eating weevil-infested rice bran? She ate the bran with live weevils for several months, as we were told it was just protein. Then I decided they spread to an extreme amount in the 20 bags I had left. So I had them fogged and now the weevils are dead in all the bags. To prevent Re-infestation, the bags were moved to an extremely cold room with AC running 24hrs. My question is, regarding my horses recent skin-related health condition. She has had severe itching all over the body. To the point of having to medicate her and give her double doses of Ivermectrin to rule out Neck Threadworms etc. All the while still eating the fogged-dead weevil infested bran…. Could this feed cause a horse to Itch that badly ?

  12. This is what my grain bags had. I baught them from( tractor supplies) went there again today to pick up grain to find grain mites infested in all the grain they had. Told woman working about it and she tried to say it was safe to feed my horses this. For someone whose taken equine nutrition classes I would know what’s ok for my horses to eat . Not getting my grain from tractor supplies company any more .

  13. Can grain mites infest wheat bran? One of our horses was diagnosed with grain mites in its stool. We don’t see grain mites anywhere in the feed. We only saw something that looked like little mealy bugs in the wheat bran.

    1. Hello,
      Yes, grain mites can infest wheat bran. The good news is that the mites are a nuisance, but are not harmful to horses.
      Good luck,
      Roy J.

    1. Hi Janice,
      The good news for you personally, is that these mites do not bite humans. The main concern is the results caused to your feed and feed room. If you do have an outbreak in your feed room, remove affected feed from the room immediately and thoroughly clean the area. Pyrethrin can be applied to the area with a hand held fogging machine or aerosol spray can.
      Best of luck!

  14. I live in Sitka Alaska, I have these horse mites,inside my home. I mostly find them in my beading containers. How do I get rid of these?

    1. Hi Victoria,
      Yikes! First off, it would probably be best to confirm that they are grain mites that you are dealing with in your home, and not something else. It might warrent a visit from an exterminator to further define what you are dealing with, and then plan a course of action.

      Best of luck!

  15. I had feed mites on my bags of feed that where on pallets. I disposed of the feed but do I need to also dispose of the pallets or is it safe to reuse the pallets?

    Thank you


    1. Hi Elizabeth,
      Sorry to hear about your feed mites. You probably don’t necessarily have to dispose of the pallet, but make sure the entire infected area is cleaned properly. Pyrethrin can be applied to the area with a hand held fogging machine or aerosol spray can.

      Best of luck!

    1. Sue: how did you get rid of the grain mites? I’m infested in my home w them. Thank you.
      S. Stewart

  16. Do grain mites infest hay? My hay was put up at 14.5% moisture into an old bank barn mow in small square bales. The entire mow became full of a fine white dust, penetrating deep into the stacks. The humidity was very high for 6-8 weeks in August and September last year. Any thoughts?

    1. Hi Karen,
      Thank you for your question regarding hay stored at 14.5% moisture with some high humidity in August and September. Grain mites would not be expected to infest hay. That said, there are some mites that do infest hay and straw. The conditions you describe would also favor development of mold and mildew on the hay and in the environment. You may want to consider sending a sample of the hay in to a testing lab for examination and confirmation of what you are dealing with. Moldy hay should not be fed to horses, so it would be good to get confirmation of what you are observing.

      Best wishes,
      Roy J.

  17. What should I do about the tractor supply in Lebanon, PA? As they have a severe infestation of feed mites. I now have to travel much further to get my proforce fuel and safe choice Maintence. I’ve tried contacting corporate as well as the DM’s. No change or action taken. But all of the nutrena and other feeds there are contaminated with mites so badly that the bag looks like it’s moving.

    1. Hi Liz,
      We are so sorry to hear you are having an issue. If you are willing to share your contact info with us via private message on our Facebook page, we would be happy to get you in touch with a local sales rep.

  18. I Have two cans that I use for feed. One is for Safe Choice Mare and Foal, the other for haystack special blend pellets.
    I put a couple new bags of Mare and Foal and had to leave town for a few days. My son called me and told me he hasn’t been feeding it to the horses because there are bugs in it. When I got home sure enough, there are thousands of mites all over the inside of the can. But when I looked int he special blend can, right beside it, there are absolutely no mites in it. So I have to assume I bought the bags already infested and brought them home. I purchased two bags from another store but really hate the fact that I wasted over $40 on grain… Is there a way to get coupons to replace the bags?

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