Monday, July 17, 2006

How To Deal with Blister Beetles in the Garden: Organic Pest Control Methods

Striped blister beetles on Straight 'N' Narrow bean leaves

June 2011 update: The other day I saw my first blister beetle of the year. Ick. Our last few springs have been wetter than normal, and this has apparently kept the blister beetles from appearing in their usual droves (hooray!).

If they start destroying the garden this year, I'll be liberally dousing them and the plants they're attacking with food grade diatomaceous earth. This amazing stuff is 100% natural and organic and very safe.

We buy this brand in economical 50-pound bags and use it all over the farm: we feed it to our livestock as a natural wormer and wellness supplement, dust the dogs with it to help with fleas and ticks, sprinkle it in water troughs to keep algae from forming, and have 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.

Food grade diatomaceous earth will last indefinitely (keep it dry) and can be used to combat all sorts of garden pests, including both hard-bodied (like sow bugs) and soft-bodied (like slugs and cabbage worms). Apparently it's also an excellent way to naturally kill bed bugs. It will not harm earthworms, but avoid sprinkling it directly on flower blooms, as it can kill beneficial pollinators.

August 3, 2011 update: Last week the blister beetles arrived in force in the pepper and tomato beds, and the diatomaceous earth is working beautifully! I liberally sprinkled it around the base of the plants and on some of the leaves, and by the next day they were almost completely gone, with no more visible damage.

You can read more about blister beetles and the many uses for diatomaceous earth in my new post, Garden Journal 8/1/11: Attack! Using Using Organic Diatomaceous Earth on Blister Beetles and Other Pests in the Garden and Around the House and Farm.

Be sure to read through the comments section below for lots more information on how to control blister beetles. And if you've had success getting rid of blister beetles in your garden, please let us know how you did it!

Realization Of The Day:
The blister beetles have arrived. What to do?

If you don't know what these horrid little creatures are, please take a moment right now to feel very, very grateful. If you are all too familiar with them and their treacherous acts of decimation in the battlefield we foolishly call our gardens, then you have my sympathy. And if the blister beetles have not declared war on you yet this year, right now you're probably taking a moment to pray to whatever or whomever it is you pray to about these kinds of things. Me? I forgot to pray.

Blister beetles devouring my Swiss chard

Last year I happened to mention blister beetles on a Farmgirl Fare post about, of all things, chocolate cake. Okay, it was about farm emergencies in general, which is why the blister beetles came up.

Anyway, a reader named Emily left me the following comment:
"Since you mentioned blister beetles, could I ask how you deal with them? We have tomato plants in our backyard garden (in Kansas), and those nasty things wiped out an entire plant in one day!

We had never heard of them before, but our extension office identified them, solving the mystery of what happened to the plant as well as my poor husband's leg. Yikes, those blisters are vicious. Any advice you have would be most appreciated!"

And this was my reply:
I was so sorry to hear about your blister beetle invasion. You're right; they are vicious—and ravenous. They can destroy your entire garden in a couple of days.

For those fortunate readers who are not familiar with blister beetles, here is a little background information on them, taken from one of my very favorite books, Organic Plant Protection, published by Rodale Press:

"The black blister beetle, also known as the Yankee bug and just plain 'blister beetle'. . . is a fairly long (up to 3/4") and slender beetle, with soft, flexible wing covers. The entire body is black or dark gray, and the covers may be marked with white stripes or margins.

Another species, the margined blister beetle, is distinguished by a narrow gray or yellow margin on the covers. Blister beetles are very active, and frequently appear in large numbers in the latter part of June and through July.

Handpicking is effective in controlling this pest, but you should protect your hands with gloves, as the beetles discharge a caustic fluid that is harmful to the skin. Some growers achieve control by dusting with equal parts lime and flour. This should be done at the warmest time of the day.

Blister beetles are usually found in swarms or colonies feeding on the blossoms and foliage of any of a number of garden and field crops—vegetables, vines, trees, and flowers."

We have both species mentioned here—the black/grey and the lighter striped ones. Last year both were out in force, and it was terrible. What they don't completely devour, they ruin with their icky black droppings.

I didn't know about that lime/flour solution until reading it just now. It sounds interesting. I would start with that as it is totally safe. Look for lime at a feed/farm supply store or nursery or garden center; it's very inexpensive.

I have read various other 'folk tale' remedies—like that they won't cross wide, empty spaces so you should either leave wide rows between plantings or once they have invaded, clear out the surrounding weeds, grass, plants, etc.

I've even read about people yelling at them to scare them away. Who knows. When I'm desperate, I'll try some pretty crazy sounding things myself.

I've never gone the hand-picking route, as there were always way too many of them—hundreds and hundreds last year. They also run fast! But that would be your best bet if you only have a few to contend with. I hope this helps. Good luck!

She came back and said:
"Thank you kindly for the information! Those terrors seem to be gone for now, but we'll know what to do next time. We thought we had gotten rid of them once, but they showed up a second time. It's good to know some natural remedies to try. Much appreciated!"

Bean and chard bed that has been hit the hardest (taken yesterday afternoon)

I saw two blister beetles in the garden yesterday morning. By the afternoon the troops had arrived and they were in full munching mode, happily making dirty lace of that poor, struggling Fordhook Giant Swiss Chard that had up to this point been eaten down to practically nothing by deer and then attacked by worms.

I snapped some photos, started getting depressed, and readied myself for total decimation by morning. A quick garden tour this morning assured me that the blister beetles were showing no signs of having filled up their small but seemingly bottomless bellies—I suppose because they immediately empty them with all that black yuck.

Attacked chard sprinkled with flour/lime mixture

I searched through Farmgirl Fare, located the above information, and decided that I had nothing to lose with the flour/lime dusting suggestion. I used all-purpose flour and limestone ('granular calcium carbonate for livestock and poultry') that I bought two years ago in a 50-pound bag at the farm supply store for under two dollars (to add to the water of the two bottle lambs I had at the time to help control scours and some other stuff).

Since it was 95 degrees F in the shade, I figured this qualified as 'the warmest time of the day' and simply sprinkled the mixture all over the plants and the surrounding soil.

I checked back later and only saw a few blister beetles, but there also weren't any in evidence on the bean plants they had been all over earlier. I wondered if they were all simply taking a siesta. I also wondered if this was such a wise idea. If I succeeded in getting them to vacate my already ruined chard, what would they attack next?

What's left of the Oriole Orange chard.

Another round of surveillance just moments ago revealed a few on the chard, a few on the Nero di Toscana cabbage in the adjacent raised bed (which had already been half devoured over the past few days by Cary and cabbage worms), and the scary remains of what had once been Oriole Orange Chard that I had missed seeing being attacked earlier.

In between these checks I launched a fairly exhaustive search on the internet for any helpful information in beating the blister beetles. I didn't find much. The highlight was definitely this incredibly significant and yet ridiculously obvious statement I found on a Texas Cooperative Extension site: Mouthparts are for chewing. At least it made me laugh.

Here's some more information about blister beetles I came across:
--The 'caustic fluid' blister beetles discharge/secrete is called cantharadin and is toxic to people and animals.

--Most of the sites I found focused on controlling/dealing with blister beetles in alfalfa hayfields, as potential injury to horses (and less commonly to cattle and sheep) is possible if they ingest blister beetles with harvested forage (the poisonous substance stays remains active in dead beetles).

--Larval stages feed on grasshopper eggs or are predaceous and are thus considered to be beneficial, although a few species feed in nests of solitary bees.

--I read more than once that blister beetles supposedly do little or no damage to backyard gardens (Ha. Ha ha ha ha ha. Oh please.).

--Those sites that did admit to the terrible destruction they are capable of usually had nothing helpful to tell gardeners to do except to practice "diligent hand picking" while of course always wearing gloves to protect your skin from the cantharadin. Or you can simply knock the beetles directly into a can of soapy water.

--The National Garden Association suggested using pyrethrum on them, and a site called Natural Pesticide In The Garden suggested sabadilla (something I've read about before but am still not sure where/how to obtain).

--A thread on the Garden Clinic Forum on was started by a woman in Southwest Missouri who said, "I am having the same problem with blister beetles.I had never seen them before. They have almost completely devoured my potatoes and were starting on a tomato plant. I've sprayed several times with rotenone. It kills them but more just keep on coming." Nobody was able to offer her much help.

In years past, I've simply admitted defeat as soon as the battles with the blister beetles began. Their surprise attacks come without warning (is that redundant?) and are short, messy, and full of horrific damage. But they usually seem to disappear just as quickly as they arrived, and I have never had them decimate my entire garden.

Once again, I won't pull up either of the patches of chard (even the Oriole Orange that is simply painful to look at right now), the Nero di Toscana cabbage, and anything else they decide to devour in the next day or two. At least some of these plants should recover and reward me with edible bounty once the blister beetles are only a hazy nightmare.

If you have any experience with blister beetles, especially if you've figured out a way to win the war with them, I (and probably many other frustrated gardeners) would love to hear about it.

But right now I'm forcing the blister beetles out of my mind so I can concentrate on cooking up the beautiful beets I harvested earlier to go with the garlic and herb encrusted leg of lamb that I just pulled from the oven.

And for the person in this household who doesn't care for beets (yippee, all for me!) there will be crispy pan-fried new potatoes (in homemade lard), along with salads for both of us made with any greens I can scrounge up in the garden and topped with slices of rosy red tomatoes that will no doubt still be warm from the sun.

Oh, the dragonflies arrived in swarms yesterday, too. That almost made up for the blister beetles. They're glorious.



  1. Oh jeez, we're having a beele year aren't we? Me with my Cucumber Beetles and you with these Blister Bastards.

    I'm soooooo frickin' tired of beetles!

    As we speak, my Kentucky Wonder's leaves look like lace because of the Japanese Beetles.

    Beets and leg 'o lamb? I am sooo there!

  2. I hear you and feel your pain. No beetles (yet!) here, but I'm slowly losing 2 pear trees to Fire Blight. I even sent away a sizeable piece of branch to our local extension service to verify my suspicions. Not much to do about it (it's caused by a bacterium). This is the down-side of growing things, but logically should be expected, no? "The Lord giveth, and the Lord taketh away," and all that.

    BTW, my extension service said that they have seen more Fire Blight in the past few years than they ever had in the past. Their explanation for it? Global warming. Time to take better care of our earth!

  3. I've got the Japanese beetles still, plus potato bug larvae (and man, they poop and eat alot!), the cucumber beetles, and the occasional squash bug. I'll have to watch for these blister beetles...wouldn't be surprised if I have those as well. :(

    Since you live SO FAR out in the country, there's probably no harm in trying the stranger tactics like yelling at them! ;-)

  4. Urg, I don't have blister beetles but I am swamped with those stupid striped cucumber beetles. Evil little things. Hand picking does not work on them either.

  5. Susan,
    Put that shuffle hoe to good use. The beetles lay eggs in the soil for next year. Keeping the soil hoed will help decrease the amount of insects in your garden next year. Mixing the top layer of soil exposes eggs to the sun,wind ,and birds. I have used a shuffle hoe in my garden for 20 years. I used to have serious problems with beetles and cutworms, but no more. Also each year leave one raised bed barren. Amend the soil, cover with black plastic, and let it bake all summer. This will kill all eggs and garden cooties:) In the early fall,remove the plastic and plant with a good cover crop. In the spring till the bed,plant, and keep non flowering veggies covered with a light row cover to keep the bugs out. Each year I do one section of my garden like this. The section gets to rest and bake for one year. It will be many years before that section gets done again. But no more bugs, and I grow an amazing amount of veggies,herbs, and flowers.

  6. Hmm, nobody mentioned dianthus sea shells and yes I probably butchered that name. I used to get them from Organic Garden magazine. You sprinkle them on the ground under the vegetable plant. The theory is that even though they do not harm us, the bugs and worms find them extremely sharp and painful (take that evil beetles!). One other thing I would do is cut the plant to the ground, feed it to the chickens (Yay!) and let it start up again hoping for a fall crop. Yes, sooner than you think. I would sooner turn the flock of chickens loose in the garden (yes, there will be loss, but you can prepare for some of it.) and let them eat bugs rather than hand pick. Yuck!

    1. chickens will not eat the beetles they run away squawking.

  7. i just *knew* you eat those sheep!

    honestly, i have often wondered. myself, i would love a source for organic lamb. your dinner sounds marvelous!

    blister beetles: oh yeah, this year was my first experience with them, though their sinister form is vaguely familiar and i somehow knew not to touch them when i first caught them eating my chard. hand picking is working for me for now. i might try the lime flour mix if the heat wave ever ends.

    i use dishgloves and flick them off the plants where i stomp them. it does wonders for my mood.

    so far they have been caught eating chard, beet tops, and tomato leaves.

    most of my reading has been like yours- hand pick, wear gloves, etc. my chickens, for the record, will not eat them. they seem to know.

    i am sorry to see the decimation in your garden. the chard should survive if it has enough to drink.

    tabitha, not karl

  8. Paint brush poet is talking about diatomaceous earth. It's the fossilized remains of marine organisms and can be used for a lot of pests. Neem spray would probably work as well..

  9. My condolences. something is still eating my basil and zucchini leaves too, but I have no idea what it is. Thankfully the other plants are ok.

  10. I had an invasion last year and the onlyh thing I knew how to do was drop them one by one into a cup of water I held below the leaves. While it didn't save the flowers, it stopped them on the tomatoes.

  11. I don't know if this would work with the blister beetles (which I am now extremely thankful I've never had to deal with), but I've had some success controlling cucumber beetles by using my dustbuster to vaccuum them up. It's definitely faster than hand-picking, and once the canister has a bunch of beetles in it I just open it up and dump them into a bucket of soapy water. I suspect you could also get results with a wet/dry shopvac, just put a little soapy water in the canister, than vaccuum to your heart's content. Very satisfying!

  12. i've seen those horrendous bugs for the first time this year, too!! they've completely ruined my garden :( this morning i put some DE with pyrethrin on them and I hope they're all dead by the time I get home.


  13. One thing that I have found to work on most garden pests is real easy to make at home, and it may help with deer.
    I found that mixing 5 cloves of garlic, 4 tablespoons of red pepper flakes, 1/4 cup of dish soap and 2 gallons of water in a garden sprayer work quite well. I use all natural dish soap which is detergent free and organic garlic and red pepper flakes. I have not used this on any tomato plants. I have a certified organic farm and there for I am very cautious about what goes into and onto my produce. The only real draw back to this is that you have to wash all produce, no more walking threw the garden and grabbing a piece of lettuce or green bean.

  14. At first I thought deer were eating my autumn clematis....until I saw blister beetles covering the blossoms. I have used SEVIN which seems to have "run them away" but where did they come from and where are they going? I see some (I think) eggs on a crape myrtle nearby....and wondered if I should spray things nearby prophylactically. Would love suggestions/info. Thanks!

  15. The person who referred to dianthus sea shells meant Diatomaceous Earth(DE) which is made from fresh water diatoms (fossil flour)and is an organic way to control insects. It is a white powder that you sprinkle similar to the lime/flour mixture only you should take care not to breathe it.

  16. Hi Suzanne,
    A scuffle can be a very handy tool to have in the garden. You'll find photos and read all about how they work at my previous post, I Can't Live Without My Scuffle Hoe! : )

  17. Yikes, saw those blister beetles yesterday when I was weeding the garden. Didn't think much of it because they weren't eating anything but this evening went out to move the water in the garden and they had desimated(sp?) my beet plants, thousands upon thousands of those grey nasty things. So I am going to try the garlic, peppers, and soap, tomorrow. My poor son who is four and has taken such pride in the garden and is using it as his first 4-H project bawled his eyes out at the sight of our beautiful beet tops. Poor little booger. I picked the beets and am now searching for a pickling recipe. I HATE BEETLES! btw when I was little we knew them as velvet bugs because they are soft to touch.

  18. A friend just told me that she handles blister beetles with her wet/dry shopvac. A little soapy water in the bottom (the soap breaks surface tension and makes the little buddies drown, instead of just climbing out of the water!) and sucks 'em up straight from the garden each evening until gone. I don't have a shop vac but I do have a handheld vaccumn with a reusable/washable filter. I've already seen some this year and plan to use the mini vac and dump the beetles in a bucket of soapy water. Good luck!

  19. What is the all natural potion for killing the cucumber beetle??

  20. I just used the garlic/soap/pepper flakes concoction on the beetles....I decided to boil the stuff & make a "tea" as I didn't want the particles to clog my sprayer. I threw in some onion for added "yuck" flavor. WOW! They curled up & died immediately! I am impressed--but also concerned: if it worked this well, could there be any adverse affects for the plants/ good bugs?
    Thanks for the tips!

  21. Blister beetles!!! We used DE and they all did disappear fast but that is not the end of them. They nest and breed in the ground around whereever they are chowing. Medina Orange oil and water will kill them but again there is the breeding ground. Since this was a raised bed we howed around edges and they came out in the hundreds. Creative thinking. We got out the turkey fryer/propane tank and set up the pot
    with water next to the bed. Pour about six pots of boiling water on the infected area which was chard. So far we haven't found any more beetles and we are hoping the boiling water killed the eggs etc.

    We often use boiling water on ant beds although we boil it on the kitchen stove. Usually takes three to four gallons of boiling water for a major ant bed. Put a rock/stone over the bed after the water is poured on to keep the steam in. Their beds are deep. Another remedy for ants is Twenty Mule Team Borax mixed with a little sugar around the opening of the ant bed. ( mix is about twenty per cent borax to sugar and usually put a half a cup on the top of the bed) Twenty Mule Team is high in boron which is toxic to the little devils. It does not take care of them 100% but usually they move on...takes a couple days to work.

  22. The folks at Arbico Organics suggest using beneficial nematodes. Apparently these tiny guys feed on the larva of ground dwelling garden pests, including blister and other beetles. Unfortunately, I didn't get a chance to try it this year and now those bottomless pits have moved into my garden by the many thousands... SO, i am now stuck having to resort to something else. I like the vacuum cleaner idea, but don't have electricity close enough... Last year i had a much smaller garden and only a limited number of the nightmares, so hand-picking was an option. Not so this time.

  23. Malathion will knock them down. Not organic, but it does do the job and quick!

  24. Hi Everybody,
    Thanks for all the tips and info to help in our battles against the blasted blister beetles! :)

    6/13/10 Anonymous,
    Woohoo! Great news about your organic victory. An no worries - garlic, soap, pepper, and onion shouldn't harm your plants at all. This is a very common and popular concoction because it can work well against so many large and small pests in the garden.

    7/3/11 Anonymous,
    Wow - I didn't know about blister beetles nesting in the ground - though I have wondered where they come from. Thanks for the great organic tips.

    7/30/11 Anonymous,
    Malathion is an EXTREMELY TOXIC POISON that is easily absorbed through the skin has been banned in many places because it is so dangerous. I would NOT recommend using it anywhere in the garden. Saving a few plants isn't worth poisoning everything - and everyone - in the vicinity.

    I strongly urge anyone reading this NOT to use malathion in your garden.

    You can read more about the dangers of malathion here:

  25. I used Home Defense Max (from Walmart) and it worked nicely. The side of our house where we store the water hose was crawling with these nasty things. And I mean the whole ground look to be breathing because of the sheer mass of them. My husband sprayed Home Defense Max on the ground, side of house, and in the small holes where they laid their eggs and by morning there were nothing but a million dead carcasses lying around! Victory!!



  27. Gardening in Kansas: have had striped, black and brown blister beetles on potato and tomato over the years. Find that Sevin dust produces near 100% dead beetles in a couple of hours. Find that Malathion is slow acting and much less effective and saw no dead beetles. No luck with Rotenone. Thanks to this forumn will be experimenting with DE, vaccume cleaners, light traps and neem. Thanks.

  28. I know I'm a little late to this discussion, but I wanted to tell you guys about how to get rid of these horrible bugs. They destroyed my huge, beautiful hostas before I could even find out what they were. I used chunks of original Irish Spring soap. (found this tip online) You can grate it, but rain dissolves it faster, so I chunked mine up (not too big tho). Then sprinkled pieces in the flower beds. Worked like a charm. Only had to do it once. I did it again the next year for good measure. I've never seen another blister beetle (I had the black ones) in my yard.


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!