What, if anything, kills blister beetles?

I may have asked this before, and if so I apologize, but since this is THE perennial problem in our gardens, I thought I would try again. Blister beetles are the most destructive garden pests I have ever encountered -- capable of wiping out an entire crop overnight (of ANYTHING! They don't seem to care what they eat as long as they never have to stop eating!) One minute there is no sign of them and the next day, BAM, your whole tomato patch is just skeletonized.

Does anyone know of a predator that actually eats blister beetles? (Or an organic way to kill the boogers?!) Our chickens won't touch them, and in fact, from everything I have read about them, they can actually kill livestock (especially horses) that accidentally ingest them. Nothing short of hand picking them by the thousands has ever worked, and that is just too time-consuming for practicality. (Plus, you have to wear gloves or get severe chemical burns from handling them.) We have been fighting these guys for so many years, we sometimes think we are going to have to build a completely enclosed greenhouse garden and truck in all new soil to avoid them! Not even squash bugs come close to this scourge!

I had an outbreak of blister beetles last year on my yellow pear tomatoes that was greatly diminished after several praying mantises showed up. I didn't witness them hunting the blister beetles, so coincidence is a possible explanation,

Striped or black?
We have only had the striped ones twice in the forty years we've gardened in arkansas. they came by the thousands to many in this county the same week a couple summers ago....very dry and hot weather. I panicked and tried all kinds of things......from pans of soapy water to a shop vac and really nothing made a dent in them. They came, they ate, and they left??? on their own time...with in a week. They ate all but the purple tomatoes vines, most of the peppers and hid in but did not eat the sweet potato vines....I can't remember anything else that they did or didn't eat....but it wasn't everything or even all of anything. I was able to replant much of it.

The black ones are worse though, I think...once you notice them they never seem to leave and spread from plant to plant...we don't have them very often but try to always watch for those first ones and kill them. I use my bare hands to knock them into soapy water but have also squished and never been 'blistered'. If we are able to catch them early though they aren't a problem.

I thought the guineas that we had briefly were eating squash/stink bugs for sure and wondered if they might eat blister beetles, but we had none to test them with. We liked having guineas in the garden once the plants were big enough to be walked on and around, they don't scratch or go for fruit like chickens do.

Dan Boone wrote:I had an outbreak of blister beetles last year on my yellow pear tomatoes that was greatly diminished after several praying mantises showed up. I didn't witness them hunting the blister beetles, so coincidence is a possible explanation,

We have lots of mantids so either the population of blister beetles is simply too great for them to handle or they don't eat them. Anyway, I doubt they could make much of a dent in the thousands we get.

Judith Browning wrote:Striped or black?
We have only had the striped ones twice in the forty years we've gardened in arkansas. they came by the thousands to many in this county the same week a couple summers ago....very dry and hot weather. I panicked and tried all kinds of things......from pans of soapy water to a shop vac and really nothing made a dent in them. They came, they ate, and they left on their own time...with in a week. They ate all but the purple tomatoes vines, most of the peppers and hid in but did not eat the sweet potato vines....I can't remember anything else that they did or didn't eat....but it wasn't everything or even all of anything. I was able to replant much of it.

The black ones are worse though, I think...once you notice them they never seem to leave and spread from plant to plant...we don't have them very often but try to always watch for those first ones and kill them. I use my bare hands to knock them into soapy water but have also squished and never been 'blistered'. If we are able to catch them early though they aren't a problem.

I thought the guineas that we had briefly were eating squash/stink bugs for sure and wondered if they might eat blister beetles, but we had none to test them with. We liked having guineas in the garden once the plants were big enough to be walked on and around, they don't scratch or go for fruit like chickens do.

We get both the black ones and the striped, Judith. I do what you do -- knock them into soapy water (I keep a few lidded coffee cans around the garden with soapy water in them so I can catch them as soon as I spot them.) And the blistering doesn't bother me much either though I will get blisters once in awhile when I am in the thick of plants that are really covered -- mostly on my arms and bare legs. They never seem to do much on my hands. It really seems to get to my husband though. I guess some people are more sensitive to them than others. I don't get poison ivy either. (However Rue once raised so many blisters on my legs that I looked like I had poured scalding hot grease over them -- even left scars for a couple of years!)

I keep hoping there is a miracle cure though -- either a simple spray of some kind (old, weak coffee is still the best remedy I have found so far) or a critter that actually likes to eat them. I would be afraid of letting the guineas eat them if I were you though. The chemical they release is apparently extremely toxic and even if it doesn't kill the guineas, it might pass make them really sick. (By the way, we decided not to have guineas because they are very hard on indigenous reptile and amphibian species and will even eat baby birds or eggs. Which is too bad because otherwise they are great to control pests like ticks.)

I don't garden like I did when my Grandmother and Mother were still around, so the following is either from memory of what we did, odd notes, and what I have picked up along the way in discussions with other gardening over the years. Hope it helps.

Meloidae are a large family within Coleoptera, and other than the massing and eating our gardens, many varieties are a beneficial as the larva eat grasshopper eggs, while others may be a parasitoid during certain stages.

One of the common of methods control is to place a container of soapy water under the blighted plants and then shaking the plant to induce thanatosis (feigning death) in the beetles, which many Coleoptera species use as a first line defense mechanism. WHERE GLOVES!

A "trap crop" if coordinated with known times of the beatles appearance can be very effective in depleting the population before hand. Pigweed (Amaranthus sp) has worked for this.

Diatomaceous earth was also very effective in reducing their numbers when properly applied.

The following I have use on limited occasions, but have received in discussion good feedback to their effectiveness.

Neem Oil, Spinosad, and direct attack with some form of organic pyrethroid spray or dust has proven of worth for some gardeners as well.

Note: The toxins (Cantharidin*) in dead beetles can lead to a condition known as Cantharidiasis if ingested by horses and perhaps some other livestock. So bury in safe location and/or burn them in small brush fire as their poisons stay active in their bodies long after they are dead.

*Note these beetles and the organic chemical Cantharidin compounds they produce have been used in folk remedies of several forms for thousands of years from "specialized poisons," dermal treatments (burns off warts), to the aphrodisiac "spanish fly," which is illegal to sell and administer in most areas due to potential of overdosing. Symptoms of cantharidin poisoning generally is blistering of the dermis (skin.) If ingested the first sign if in large does is burning of the mouth lining, then dysphagia, nausea, hematemesis, gross hematuria, and dysuria. Mucosal erosion and hemorrhage is seen in the upper gastrointestinal tract.

Jay C. White Cloud wrote: A "trap crop" if coordinated with known times of the beatles appearance can be very effective in depleting the population before hand. Pigweed (Amaranthus sp) has worked for this.

Unfortunately, for us, this doesn't work. Our blister beetles seem to love everything that grows. They would just eat the amaranth and move on to the next course.

Jay C. White Cloud wrote:Diatomaceous earth was also very effective in reducing their numbers when properly applied.

We tried DE as well. It was a definite no go. In fact, we have tried DE on several problem insects in the past (including once when our dogs got a flea infestation) and it has never really worked for anything. I honestly do not know why it has such a reputation for insect control. About the only thing we have ever found that works -- even remotely -- on blister beetles is soapy water. Coffee sprayed on them works too, but much slower, and the down side is that you have to soak each one individually to kill them, so you may as well pick them off and drop them in the soapy water. Neem oil is okay too, (we did try it at one point and found it about as effective as coffee -- and with the same problem that you have to make a direct "hit" on each bug to kill it) and way too expensive an option for us, since our gardens are huge.

I guess there really is no other viable option. I keep hoping for a miracle, but it looks like old-fashioned hard work is the only answer.

I once worked as an intern on a market garden, I would wake up right before sunrise, with a flash light to go on slug controll. The particular flashlight I had was also a stun gun. I would zap slugs and beetles on my early morning patrols. We did the soap and neem sprays, but just like everyone mentioned, direct kill was the most effective. There was a noticeable difference when our wasps hatched and ate the eggs, and when predator insects were in season in general. I've heard using a 'stirup' or 'sc/huffle' hoe in early fall, exposes the eggs to the sun and destroys them. Without tilling hard. I have heard rumors of making ground level potato skin beetle traps. Never used them. Not a problem near me. Thankfully

I am being plagued by a bug. It turns leaves yellow and then into swiss cheese. Only seeds planted before the last frost survive (peas) and purple plants (red lettuce). Is it the blister bug from your thread? Because at this point, its even destroying the zucchini. I covered the garden in coffee grounds and its not helping. Dish soap is next. Its been this way for several years. The robins aren't interested in it.

I realize that this is an old post but since there were no tried and true solutions offered, I thought I would let you know what we do for dealing with blister beetle infestations. Might help someone else who is encountering them for the first time!
We get three different kinds of blister beetles. They come in waves. The black and grey ones, then the tan ones and then sometimes the bigger solid black ones. They are all voracious eaters and can decimate plants in hours if we are not paying attention. Around here they mostly go for our bolting spinach( hard to save seed around here), chard, potatoes and lambs quarters and amaranth which I leave growing as a trap crop.
The first time we saw them we were freaked out! We had never seen anything like them. There were thousands of them on each plant! Caused a few nightmares. We used a small shop vac to suck them up but dragging a cord around the huge garden got tedious.
We discovered that dish soap works well to kill them. About 1-2 TB per spray bottle of water. We use a natural brand and go through several bottles of dish soap in a season of BBs. They have to be sprayed directly and we enjoy watching them writhe for a few minutes before dropping to the ground dead. Some of them die still hanging on the plant. Of course, then we can't eat the plant or feed to the goats, in the case of the weeds that are sprayed, but after the infestation is over, we will cut back the damaged leaves and new ones grow back.

What natural soap are you using and how big of a spray bottle? I don’t know whether to use a 16 oz or a 32 oz to get the correct mixture.
These dang beetles are in our pig pen on the tomato plants. Plus the plants are growing through the fence where the goats or cows could possibly eat them. I need to end it right now before it kills something besides a tomato plant.

This is an interesting topic and it appears that there is not a one size fits all remedy.  Because I was not sure what the blister beetle is, I did a web search and found this information which may be useful as a background or guidance document:  https://morningchores.com/blister-beetles/ Big take home message is ensure that you have good quality PPE when dealing with these beetles.  It has not been said but perhaps the affected plants could be put into a black bag and exposed to the sun to kill the beetles by cooking.  Diligence is the key to control.

Hi Lavenia,

Welcome to Permies.

I know this is an old, very old post. But I recently stumbled on it while seeking a solution to the invasion of hundreds of ash gray beetles, that stripped my garden to stems in a week. Based on something I read here, I put about 1/4th-1/2 cup 7th generation liquid dish soap in a 1 gallon pump sprayer of water and began my war. Within 3 days I have virtually zero. This has beaten the bastard beetles back, with no harm to the host plants and no residual pesticide. The larvae live on grasshopper eggs, so if you have a high grasshopper year, ( as I did in 2021) get ready for  and explosion next year.