Monday, August 01, 2011

Garden Journal 8/1/11: Attack! Using Organic Diatomaceous Earth on Blister Beetles and Other Pests in the Garden and Around the House and Farm

This was supposed to be a short post about the blister beetles, but once I get started talking about diatomaceous earth it's hard for me to stop because it has so many great uses. Even if you're lucky enough to not know what a blister beetle is, you may still want to read on.

A blister beetle sighting in the garden is always distressing.

Realization of the Day:
We've reached that point in the growing season where the fact that I (once again) didn't get around to planting everything I wanted to in the spring has actually turned into a good thing.

As in, it's a good thing all these raised beds aren't full, or I'd be spending a lot more time standing out here in the blazing sun watering (although I am loving my new 150 feet of super lightweight Water Right garden hoses—and wish I'd bought these awesome brass quick connectors 17 years ago).

Or, it's a good thing there isn't more stuff out there for the blister beetles to eat.

It's a twisted way of looking at the bright side that usually works for me.

The blister beetles—who seem to prefer hot, dry weather—have arrived, and they are hungry. So far I'm mostly seeing them in the pepper and tomato beds, and sometime while I wasn't paying attention during the last 48 hours, they managed to devour an entire small pepper plant and decimate several large tomato plants. And their disgusting black droppings are everywhere.

Unfortunately I'm not the only one being attacked; one of the most popular posts on In My Kitchen Garden over the past few weeks has been How To Deal with Blister Beetles in the Garden: Organic Pest Control Methods.

Lots more below. . .
If you're wondering what to do about blister beetles, you may want to check out that post. And don't miss the comments section, where other gardeners share their tips and experiences getting rid of these horrible, ravenous creatures. One reader explains that blister beetles nest in the ground (not something I was thrilled to learn) and tells how she used boiling water to flush them out.

Kelly, a master gardener in New Jersey, recently posted on the Farmgirl Fare Facebook page (where I announce all new In My Kitchen Garden posts) that a friend of hers sprayed the blister beetles with an organic product that contained spinosad, then followed up with the lime/flour mixture I mentioned in my blister beetle post, and they haven't seen any blister beetles since.

I wasn't familiar with spinosad, but it sounds like interesting stuff. I found several organic spinosad sprays available, and they're supposed to work on ants, beetles, fleas, leafminers, tent caterpillars, codling moths, squash vine borers, bagworms, spider mites, thrips, Colorado potato beetle larva (ooh!) and more.

Apparently spinosad, which must be ingested by the insect to kill it, is a naturally occurring soil dwelling bacterium that was discovered in an abandoned Caribbean rum distillery in 1982. Have you ever used it?

I was just out in the garden rustling some of the pepper plants and then stomping on the blister beetles that ran out from under them. This works on small swarms—and your aggression—although if the ground is soft you have to stomp really hard or they'll just get back up and start running after you lift up your boot.

There were only a few of them visible on the big attacked tomato plants (do they mostly eat at night?), but I went ahead and sprinkled the plants and the ground liberally with food grade diatomaceous earth, which I've been meaning to write about for ages because it's such wonderful, versatile stuff. I also sprinkled it all around the base of the pepper plants and smaller tomato plants.

I'm hopeful, as other gardeners have mentioned that they've successfully used it to kill or repel blister beetles. Update: It worked! But the trick is to liberally douse the plants just as soon as you start seeing a few beetles, before you have a bad infestation. Read my July 2012 blister beetle update here.

It should also take care of the voracious tomato hornworms I have so much trouble finding, despite their enormous size, because they're amazingly good at camouflaging themselves among the tomato leaves.

Fortunately right now the blister beetles only seem to be eating the tomato leaves, though I've seen them chomp their way through the fruits, too. It's worse when they attack things like Swiss chard, because what they eat is what you eat.

Food grade diatomaceous earth isn't 'earth,' but the fossilized remains of microscopic shells created by one celled plants called diatoms. This fine powder, which looks like glass shards under a microscope, is 100% natural, organic, and safe.

It kills by physical action, not chemical, by puncturing the insect's exoskeleton with its sharp edges and absorbing its body fluids, so an immunity to it can't be built up. It's safe for people, pets, and the environment.

Food grade diatomaceous earth can be used to combat all sorts of garden pests, including both hard-bodied creatures—it works great on sow bugs, also called rolypoly bugs—and soft-bodied creatures, like cabbage worms and slugs. And hopefully blister beetles. Apparently it's also an excellent way to naturally kill bed bugs, and many people use it indoors on earwigs, silverfish, and cockroaches.

We buy this brand in economical 50-pound bags (if you can find it locally, it may cost less since it's heavy to ship) and use it all over the farm as well as in the garden: we feed it to the livestock and dogs as a natural wormer and wellness supplement (and once it passes through the animals' systems, it's supposed to keep flies from laying eggs in their manure), dust the dogs and cats with it to deter fleas and ticks (be sure to keep the dust away from their faces), put it in water troughs to keep algae from forming, sprinkle it around pet food bowls to keep ants away, dust the bottom of garbage cans with it, and spread it on donkey manure piles to keep to keep fly larvae from developing.

We also sprinkle it inside chicken coops, nesting boxes, and where the chickens like to take their dust baths.

We've even started taking small daily doses ourselves (up to 1 Tablespoon, mixed in water or juice), as it's supposed to help with everything from joint pain to detoxification. Start with just 1/4 teaspoon and work up to a larger dose.

You can use a duster to apply diatomaceous earth in the garden, and although we have two of them, I usually just sprinkle it by hand, which is easier but less efficient. After you water or it rains, it must be reapplied.

You can also mix diatomaceous earth with water and spray it (we use a small sprayer like this), which is a good way to completely cover your plants and keep from inhaling the dust. Mix 1/4 to 1/2 cup diatomaceous earth and 1 teaspoon of liquid soap per gallon of water. It coats the plants and starts working once it dries. This is supposed to be an excellent way to kill aphids.

There are dozens of other uses for diatomaceous earth around the home and garden, including many that I haven't tried, like spreading a paste on tree trunks to keep off insects, mixing it with water to make a metal polish, cleaning sinks and faucets with it, using the paste as a face mask, adding it to stored grains (both in the pantry and on the farm), or using it to soak up carpet stains or oil on a garage floor. Some people even brush their teeth with it.

When we were building our new house, we sprinkled diatomaceous earth inside the walls to deter insects; this barrier will last indefinitely. You can also use it in attics and basements and around the perimeter of buildings.

Be sure to buy 100% pure food grade, not the diatomaceous earth sold in pool supply stores. Check the label to make sure nothing else has been added. Look for food grade diatomaceous earth at farm stores, some garden centers, restaurant supply houses (it's used to filter deep fryers), or order it online from

Larger bags are a much better buy; I've seen one-pound boxes selling for $10, compared to $20 for 10 pounds including shipping. It will last indefinitely if you keep it dry.

Food grade diatomaceous earth will not harm earthworms, but avoid sprinkling it directly on flower blooms, as it can kill beneficial pollinators.

Are there blister beetles in your garden this year? What plants are they attacking? Anything they don't seem to like to eat? Do you successfully control them using organic methods? Do you use diatomaceous earth for anything?

We're all in this fight for our homegrown food together, so do tell!

©, heading back out to continue the battle.


  1. I've seen them on my Swiss Chard (when it started going to seed), but so far, not on my tomatoes like they were last year! I came to your post last year and ended up using the lime/flour solution...they eventually left.

  2. Yikes, those guys sound horrible! I haven't seen blister beetles in CT, but did just find a tomato hornworm the size of Texas eating my aconcagua pepper plant (thanks for the great suggestion :)) almost to the ground! Strong sucker, sooo gross! Susan, my fabulous husband did discover those brass hose connectors about 25 years ago and we love them. Terrific investment. I am too cheap to invest in your cool hose, so far. Thanks as always!

  3. Was reading an article about bed bugs and this was mentioned. First time I had ever heard of it. Very interesting.

  4. The only place we could find locally that stocks diatomaceous earth was the local wholesale food place, the kind of place where they buy huge amounts of things and re-package it to sell cheaply in a no-frills store. It's sold there as a human health product, but only in small amounts. Nowhere else has it--not the farm store, the garden centers of the big box stores, or even the fancy garden center and nursery that has everything else. Annoying.

  5. Hi Hannah,
    The blister beetles in my garden LOVE Swiss chard. I only have it growing in the greenhouse right now (where I've thankfully only seen a few blister beetles so far), which I figure is another one of those 'good things,' as I'm sure any in the raised beds outside would be history. ;)

    So glad you're enjoying the Aconcagua peppers - they're still my favorites. Your comment about the tomato hornworm the size of Texas made me laugh. They really are too big, like they're out of James and the Giant Peach or something.

    I LOVE my new hose connectors. Unscrewing hoses is one of those little things that drives me nuts, and for years I wondered why somebody hadn't invented such a thing. Who knew? ;)

    As for the Water Right hoses, I totally recommend them. A 50-foot, 1/2" hose weighs just three pounds, and I no longer destroy plants while yanking 100 feet of heavy hose around the 4'x8' raised beds - yay! My stress level is down, too, LOL. Definitely one of the best birthday presents I ever received.

    Unfortunately pure food grade diatomaceous earth can be hard to find. Do you have a restaurant supply house in your area? You might check with them.

    Otherwise, I would definitely go ahead and order some online. Even with shipping, a 50 pound bag is still only about $60, and it should last you quite a while.

  6. Hi Susan. I 'discovered' diatomaceous earth a number of years ago and have been an avid user ever since. We don't have blister beetles here, but we do have cucumber beetles, who love green beans, and they are handily dispatched with the earth. Great post!

  7. Susan,I had no idea blister beetles were so bad in the garden. I don't have a problem here thank goodness. We worry about them for a different reason. They seem to like alfalfa hay ALOT. We don't feed our horses alfalfa, but if a horse ingests even a part of a blister beetle, it will most likely kill the horse. Horse people fear blister beetles! ~ liz

  8. Hi,
    My first post, as I am a new subscriber to your site.

    Does diatomaceous earth, help to eliminate small inside ants? I have tried numerous products. Nothing works longterm.

    Thank you.

  9. Wonder if I sprinkled it on the lawn (I have three dogs and lots of flies in the summer, might it keep flies down or stop the little buggers??????

  10. Hi Christine,
    It's great stuff, isn't it? Thanks for letting us know about the cucumber beetles!

    Hi Liz,
    Yikes, that's scary. I know when I was first researching how to deal with blister beetles back when I wrote that original post in 2006, most of the info online was about controlling blister beetles in alfalfa fields.

    Hey Anon,
    Welcome to the farm and garden! I've used diatomaceous earth on ants - and in fact right now I have thick circles of it sprinkled around the dog food bowls on the covered porch off the kitchen, around the cat food bowls on the kitchen floor, and around the garbage can in the kitchen.

    Sometimes it works really well, and sometimes the ants crawl right over it - I think it depends on the type of ants. It's definitely worth a try, especially since there are no toxic chemicals involved. And if it doesn't work, you know there are all sorts of other things you can do with the rest of your d. earth! :)

    Hey Gramps,
    It's always nice to hear from you. If the fly problem in your yard is due to dog doo, you can sprinkle diatomaceous earth right on the doo. That's where the flies tend to breed (and in wet areas), so spreading it all over your lawn probably isn't necessary.

    You can also feed d. earth to the dogs. Besides being good for their overall health, it will help against internal parasites, and the d. earth that comes out in the doo will help keep down the flies as well.

    Mix up to 1 Tablespoon per day into food (you can even sprinkle it right on dry kibble) for smaller dogs and 2 Tablespoons per day for dogs over 50 pounds.

    Besides using d. earth, we've found two ways to combat flies on the farm that work really well for us. The first is all natural traps. I've been using Rescue disposable traps for over 15 years, and they work better than any of the other traps I've tried. They come in two sizes: the regular size (click here for more info and/or to order online) holds up to 10,000 flies, and the big bag (click here) holds up to 40,000 flies.

    They do have a strong odor (that gets stronger when the trap starts to fill up), but it usually doesn't waft very far from the traps - and it's definitely better than flies. :)

    For the past several years, we've also been ordering bags of fly parasites from Kunafin. They work GREAT. We scatter the first bag in early spring and order a bag each month through summer and sometimes into fall, depending on the weather and the fly situation. Using these tiny parasitic wasps (which you release before they hatch) has dramatically cut down our fly population.

    Hope this helps!

  11. Hi... just "found you" ... love this info!
    Tried to post a month ago and ,... duh, my kids call me a techno
    dork ... couldn't figure out how to post a comment..
    so hope this works.

  12. I seriously need to invest in some diatomaceous earth! Bugs devastate so much of my garden. Annoying.

  13. I've never heard of, nor seen a blister beetle, but here(Ontario)the Japenese beetles are the terrors. Our newly planted mini orchard has been totally consumed and now they are on to the pole beans, once those are done, they will finish off my basil plants. I've tried all the oil/soap/hot pepper solutions, they seem to spice things up for them,I've tried hand picking them into soapy water, but they out-number me. We hung sticky fly tape but they caught every bug know to mankind, but not one Japenese beetle. The actual Japenese beetle traps that they sell, with the sex hormone in them, well that just seemed to attract them for a big orgy.

    So this year we got ducks and chickens to do the job for us, pick the larvae out of the dirt so that they might not be here next year. Built them a coop that cost way more than the fruit trees, and a duck pond, but now they will not go out there because we have a hawk that is circling and has already gotten two chickens. So we can either sit out there with a gun like the Clampetts and protect the birds doing there job or have to figure out some way of fencing them in and around the trees, even from the top.

    Has anyone had any luck with this d. earth on Japenese beetles???? because right now, $60 for a 50 pound bag sounds pretty good. At least the birds are giving us eggs and an endless supply of manure, because the bugs still rule around here.

  14. Hang the traps far from the trees you want to protect. Yes, it does attract Japanese beetles. De is probably best bought online for the best deal. Granaries and places with hay and alfalfa stored use DE. Yes, your beans have DE sprinkled on them. Maybe you could contact one near you to find a source.

    I just posted on my blog about DE a few hours ago.

  15. We use Diatomaceous Earth to filter our wine. Lots of wineries do. I thought it was only a product used on wines. Good to know all these new uses.

  16. Here in Spain on a eco gardenblog there´s a hefty discussion going on between a representative of the firm that is going to sell DE to private buyers and a longterm eco gardener who used DE in his garden and didn´t see just the bad bugs disappear, but each and every bug on the spots where DE was used. He is very concerned about earthworms. How can the product repell slugs and not repell earthworms? With every watering or rain DE will sink further into the ground and with tilling will be mixed in as well.
    Would love to hear from anyone with experience longer term use of DE in a veggie garden.

  17. Hi Everybody,
    Thanks for all the great comments! :)

    I've used diatomaceous earth in my current organic kitchen garden for 10 years, and the soil is full of earthworms. It's also teeming with all kinds of other insects - both good and bad. :)

    It's my understanding that earthworms' bodies have a different kind of makeup than other worms/parasites, and so the d. earth won't kill them. And it also won't kill microscopic beneficial organisms in the soil.

    Apparently many earthworm farmers use d. earth to treat their worm beds for parasites, fungus gnat larva etc.

    What you don't want to do is sprinkle d. earth directly on earthworms.

    You should also avoid sprinkling it directly on blossoms, as it can be harmful to some beneficial pollinators.

    A Google search for 'will diatomaceous earth harm earthworms' or 'diatomaceous earth is safe for earthworms' will give you all sorts of results you might find interesting.

  18. Nicole,
    I haven't tried d. earth on the Japanese beetles, but a quick Google search for 'organic japanese beetle control diatomaceous earth' looks promising, though some sites just mention it working on the grub stage of the beetles.

    I would definitely give it a try!

  19. I am so glad that you posted this when you did. I had been looking everywhere on the internet to try and find what these 'black and orange striped beetle hordes' were, for hours! Eventually I gave up and decided to read some blogs, and lo and behold, you had a picture up of the unknown little bugger.

    Fantastic! Under your advice, I picked up a bag of DE from amazon from your link (hope you get some commission from that!). I am happy to say that all of the beetles have vacated.

    It works so-so on the hornworms... I still go out and pick some off, but there are significantly less since spreading DE over the tomatoes and peppers.

  20. I have used DE for years and last year used it on my roses and Filbert tree for Japanese beetles. It worked wonders. I did reapply it every time it rained or I watered, but it killed the beetles. DEAD.

  21. Happy to see a post on DE. I bought food grade DE from a local nursery past weekend. I live in Seattle, and slugs are a big problem here in PNW. I had read somewhere that DE can help get rid of slugs. I sprinkled some in my garden as soon as I came home. I haven't seen any signs of slug activities near my lettuce starts since then.


March 2013 update: My apologies for the inconvenience - I know word verification is a pain - but I've had to turn it on to help stop the ridiculous number of anonymous spam comments I've been getting every day. Thanks for your understanding.

Welcome to! Thanks so much for taking the time to write. While I'm not always able to reply to every comment, I receive and enjoy reading them all.

Your feedback is greatly appreciated, and I especially love to hear about what's going on in your own garden. I know, too, that other readers also delight in reading about your garden successes, failures, helpful tips, and lessons learned. Feel free to leave comments on older posts!

I try my best to answer all questions, but sometimes it takes me a few days to get to them. And sometimes, I'm sorry to say, they fall through the cracks, and for that I sincerely apologize.

I look forward to hearing from you and hope you enjoy your visits to my kitchen garden!