Blister Beetles

Blister beetles do not have a toxic bite or sting, but if you crush one of these pests you can wind up with small blisters on your skin several hours after contact due to the secretion of cantharidin (a toxic compound in their bodies).

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Grey blister beetle (top left), Black bister beetle (top right)-photos United Agri Products


Blister beetles have very long thin cylinder-shaped bodies with large heads. They are about 2 cm long (from ½ to 1 inch in length) and relatively easy to identify because of the distinct “neck-like” section between the body and the head. They usually fly around in groups and there are many types of them. They are grey, black and striped with some species shiny black-blue, or black-green.


Blister beetles are found in most parts of the US and most parts of Canada. It is the adults that cause most of the damage. Fortunately however they don’t stay around an area too long so the best control is to let them run their course unless infestation is severe. They overwinter as semi-pupae in the soil and emerge in the spring and molt. Adult blister beetles emerge in the summer months.

Life cycle of blister beetle
Life cycle of blister beetle-NC State University

Diet & Damage
Blister beetles eat the leaves and flowers of most plants… peas, beans, potatoes, turnips, tomatoes, many other veggies and flowers. They can defoliate plants in no time. The larva have been known to eat grasshopper eggs so they are somewhat beneficial. In some cases where these beetles are severe on alfafa, farmers must take caution when cutting as their livestock can die from ingesting dead blister beetles. The condition that affects livestock after eating grains infested with these beetles is called Cantharidiasis

How to Control Blister Beetles Naturally

  1. Hand Pick – Be sure to wear gloves or use tweezers as they can release a substance that causes blisters on the skin. Drop them in hot soapy water. Be sure not to touch them even when they are dead as they can still cause painful blisters on your skin.
  2. Keep Weeds Low – Weed around edges of your garden attract blister beetles because of grasshopper eggs. Eliminating the weed problem will help control infestation.

* A word of warning, killing them is not a good option unless you dispose of the bodies. Their poison stays in their bodies long after they are dead.

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  1. Melissa says

    i have black oil blister beetles on three rocky acres with little grass. I have sheep and horses. These things are gone all summer and return in fall. Been here two years. Thousands. I have tried ^&%%% dust and dawn with water no luck. Now I hand pick each day. There is little grass on property. They just don’t seem to follow the norm. What would you do to get rid of them. Have lost a pony to them.

  2. Hercy says

    The following method eradicated the beetles:
    Beetle story began yesterday. Unwittingly, squished the blister beetles on the tomatoes with bare hands.
    Today the population had quadrupled. Uncheerful about the beetle assault. Need to turn the invasion around.
    To the medicine cabinet. Scissors, tweezers, latex gloves, listerine. Next under the sink: Dawn Soap and Baby oil. Fridge: Garlic oil & Liquid “C”. Teaspoon. or so, of each ingredient, mixed into a large spray bottle of water.
    Previously ticked: Mosquito interference. Garbed in boots, jeans, & white long sleeve shirt.
    Prayer: God promised dominion over wild life. Want a 1 day war for victory.
    Little pause for wisdom and blessing.
    1st did implement others Blog tips (Thanks John and Melvin): Removed mulch and obtained a sturdy (field) weed.
    After spraying and cutting off the heads of captured beetles – Checked tomato plants couple hours later…Result No beetles. Checked later in day, A handful of hiding beetles appeared. Cut their heads off and left them as an example on the tomato leaves. 2nd morning one sick beetle. P.M. No beetles. Plants unscathed by the spray. Greatly appreciate the blessing.

  3. Sandra Robinson says

    Thanks for these ideas. We grew two different types of potatoes, red and brown. They ruined my red potatoes first and now have moved on to the brown ones. I’m so tired of them that I started cutting the stems to soil level and putting them in a large black contractors trash bag, tying it up quickly.. It is only July and hope we have some potatoes to show for all the hard work we put into them since early spring. I did not use mulch, just kept mounding up soil as they grew.

    I never seen a blister beetle before this summer. A few years ago, we started a small potato patch and it did get weedy a bit and the plants just disappeared. Now I know what happened to it. Didn’t grow any again until this year. Did a big patch and it has been nothing but a blister beetle nightmare!!

    I have used gloves to hand pick off bugs and throw them in a bucket of soapy water (along with all the other beetles bugs our garden.. There is just so many of them. I read all of the responses here and like the vacuum idea with old panty hose. I don’t like grabbing them by hand, some times they crawl up my glove, and I start freaking out.. Not fun.. Although the rest of the family finds it funny.. I will also spray with pepper and garlic sprays if they move to other garden plants. I will use my pump sprayer, easier than hand sprayers.
    I just graduated from Lansing Community College with a degree in Horticulture Landscape. We learned about landscape plants, not to much about fruit and veggie gardens. I do self study every chance I get. Which is often. Thanks so much, Sandy

  4. John says

    An update on my post of July 4…

    We’ve had 4 invasions of blister beetles this summer. 2 were major, 100s or 1000s of bugs, in repeated waves, lasted for several days — turned parts of the garden to sticks within a few hours; and 2 invasions were minor (maybe fewer than 100 beetles) and quickly wiped out. I’ve now seen 3 species of blister beetles: (a) one that’s mostly grey with a little black, and these come in herds; (b) one that’s black with small orange triangles on the abdomen behind the wing covers, and these are ‘solitary’ — just a few at a time; and (c) one that’s yellow & brown striped on it’s back; these were the most common in Missouri when I lived there; I’ve seen only a few of them late in the summer here in Arkansas.

    …about the Pyrethrins: The brand is “Bonide” concentrate, 1% pyrethrin. We ordered this thru the local Ace Hardware — $20.99 for 8 ounces — and now the local health food store carries it in their garden section. Since then, I’ve Googled “Bonide pyrethrin”; found for about half that price, but haven’t bought any yet.

    But Bonide is VERY expensive compared to the “Safer” soap: $94.00 + shopping for 2-1/2 gallons from American Arborist Supplies… for the Safer soap, that works out to $0.73/gallon of mix; for the pyrethrin, $3.77/gallon of mix. Buying the Bonide from the Web (at about $12 for 8 oz) would make it be ~$2.25/gallon of mix….

    Anyway, the pyrethrin takes out the bugs pretty quick — perhaps faster than the soap, and seems to take only a minor contact to kill them. The pyrethrin appears to be a nerve poison – when sprayed, the bugs become disoriented, ‘clumsy’, and lay there and twitch until they die.

    Summary: I use the soap whenever I can because it’s much cheaper; I resort to the pyrethrins when it’s all-out war!

  5. Bob says

    For organic control I have had success using a rotenone / pyrethrin solution. Barely soapy water helps as a medium. Frequent pm showers frustrate since the insecticide breaks down so easily. Will remove weedy areas from deer netting surrounding garden area and report later. Am located in Shen. Valley of Va.

  6. Pam says

    I’ve had infestations in the past and they are always located where the weeds are the thickest. Keep your plants weeded and you will be able to see right away when they come a nibblin’. In the past I’ve used insecticides and it did work, but I’m trying to grow insecticide free this year, hand picking bugs daily. Unfortunately with the heatwave(117 degrees) and drought this year I let a small area grow weeds and well, I’m sure you know what happened. So the last couple of days I have been killing all the bugs by hand. I thought the danger was getting bit by these things and learned the hard way yesterday that is not the case. I apparantly touched my chest at some point and in no time at all I started having a severe buning sensation when touched, ignored it and continued picking bugs. Last night when I was getting ready for my shower I brushed against my chest and the pain was severe. When I touched the area again(to examine the spot) it burst open with the slightest touch and ‘water’ ran down my chest, it burst like a water balloon. Well, I learned the hard way and hope someone will read this and benifit from my experience. I will definately wear gloves from now on!

  7. John says

    In NW Arkansas, SW Missouri. I’ve fought “biblical infestations” of various varieties of blister beetles for some years.

    Ways that I’ve controlled them:
    (1) first of all, get rid of any loose mulch, dead leaves, stalks, etc., on the ground under and around the plants — bug’s main defense is to drop off the plant and hide in the mulch. They’re harder to kill when you can’t see them! When they’re hysterically running around on bare ground, you can spray, stomp, cuss, whatever.
    (2) Various things work to poison them: (a) Safer insecticidal soap: 2.5 oz/gal of water (b) Joy dish soap: mix in about the same proportion; I prefer this to Dawn because it seems to contain fewer perfumes, etc. You have to get the bugs thoroughly ‘wetted’ with the soap water — the ‘fumes’ or lite spraying aren’t sufficient (c) Pyrethrin (brand still unknown): we’re just starting to experiment with it — email from my neighbor this morning says it kills quick; 3 Tbs/gal of water — don’t yet know the strength of the pyrethrin itself.
    (3) mechanical harvesting years ago: on my swiss chard and beets, I placed a Fiberglas restaurant tray on each side of the row, bumped a few plants, bugs fell on the trays, slid the bugs off into a 5-gal bucket of soap water. Drowning in plain water won’t kill them; I let some float in water for nearly 24 hours and then dumped the bucket on the ground. Eventually about 80% of them recovered and walked off…
    (4) mechanical harvesting #2: I once had a potato patch that was heavily infested. These potatoes were grown by placing seed potatoes on the yard grass, covering w/ 12″ to 18″ of hay mulch. To harvest the potatoes, I slowly rolled up the mulch, potato vines, and blister beetles (‘slowly’ to give the beetles plenty of time to re-hide in the mulch). Then I covered the whole pile of mulch/vines/beetles with a big tarp and piled dirt all around the edges to ‘seal’ the bugs underneath — I could hear ’em scratching to get out; eventually things got quiet…

    The invasion is about over, but I’m experimenting with mulch the bugs can’t hide in — specifically coarse oak sawdust (not the fine stuff that’s more dust than particles). This has the benefits of hay mulch (my usual) — water conservation, weed control, etc, — but the bugs run on top of it instead of hiding in it. Stomping doesn’t work because the sawdust us too loose, but you can sure see and spray ’em easier!

  8. Jule says

    Our Missouri garden is under attack from Blister Beetles! We are in a drought this year and I am wondering if this extreme weather is playing a part in the infestation. Do they eventually move on and bother other gardens on their own? Does anyone know their habits? What months of the year do they tend to show up and when can I expect to see them GONE?? Is it only a frost that will kill them? Or will they only be happy and leave once they have eaten every vegetable and flower in our garden?? Hand picking them is not an option as their numbers are staggering! (on a par with a plague of biblical proportion!) Several websites have recommended the chemical (not organic). I would appreciate any advice on how to control/kill them…as they have arrived in large numbers…and all our hard work in the garden is being destroyed!

  9. Peter S. says

    Gosh, I didn’t know what they were and I’m so used to squishing Japanese beetles with my fingers, I did the same with these. They were the gray variety. I did not get blisters, though I killed many. I will be more careful next time, but for any who have been exposed at least you know the end results aren’t always bad. BTW: I’m very sensitive to lots of things, including poison ivy.

  10. Melvin Howerton says

    I just sprayed an infestation on my solarfire tomatoes, They were the grey species.
    A few years back I had an infestation in my potatoes,They were cleaning them out badly, I took a large weed from the field and beat the plants where they were and drove them out.This is the truth, try it cause I got a blister on the back of my knee joint and it like to never healed, so I don’t touch them. After I drove them out they didn’t come back, they have a herd mentality and will just keep going once driven out.

  11. karyn mcb says

    Hi, I’m a pest control professional in Arizona. For control, nothing beats having a knowledgeable professional providing the treatment. Find one that has Turf and Ornamental credentials, preferably. Unfortunately, response time is critical; your garden or ornamentals can be completely defoliated in a remarkably short period of time. As an emergency measure, and to buy enough time for a technician to arrive, mix up some dish soap (I prefer Dawn)and water in a Windex-type spray bottle and target them individually. I’ve also been known to put a nylon stocking over the end of a vacuum cleaner hose (sometimes with multiple extensions attached so I can reach further), suck a bunch onto it, tap periodically on edge of bucket with soapy water so they fall into it, grab more, repeat, repeat, repeat.

    For blisters, the exudate needs to be neutralized to begin experiencing relief. Being slightly oily, warm, soapy water will help start breaking it down, and I’m a big fan of Boric Acid Powder washes (can also be used as an eye rinse–FOLLOW LABEL DIRECTIONS!).

    Good luck to you all.

  12. Daniel says

    Last year we woke one morning to an infestation that was on par with a plague of Biblical proportions. We tried several things in a desperate attempt to save what we could and nothing seemed to work. Then as the day got hot they moved into my cucumber trellis, it is made from metal cattle panels so I took a weed burner to them. When it was over there was a layer almost an inch thick under the trellis and the rest moved out of the garden the following day. I at least saved the tomatoes.

  13. J.B. says

    We had huge infestation of blister beetles (ones w/yellow stripes) and we found that spraying the tomato plant down with soapy water worked in getting them off the plant but then when the soap bubbles went away, they scattered so you stomped on them. It would have been great to knock them into the soapy water but we had cages around the beetles. They destroyed our swiss chard, moved to the kale, almost destroyed our tomatoes, destroyed almost all the pepper leaves, on the sweet potatoes and okra. They love to hide so get rid of the straw or cardboard mulch. We also picked them off by hand at night since they were easier to pick off w/o harm, but my husband did get one on his collar and it gave him 3 blisters which they say will go away. We also sprayed a hot cayenne pepper spray at night which seemed to kill them, too. Good luck!

  14. Patsy says


  15. Kathy says

    My 2 year old grandson had horrible blisters on the right side of his neck and shoulder from this bug. His mom took him to the doctor and he popped them. They are about two inches long and an inch wide they look horrible. I have seen these bugs everywhere just didn’t know what they were. Thanks to this web site for the great information and hints on how to take care of him. Thanks to all.

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