Spanning from the Meloidae family, blister beetles are nasty little bugs with a chemical defense called Cantharidin. This chemical is toxic to humans and animals  and may cause haematemesis, dehydration, blisters, and even renal failure if swallowed.
If eaten by an animal, even one as big as a horse, it only takes around five to ten to be fatal . With this in mind, it’s imperative you properly identify these pests and get rid of them as soon as possible.
All blister beetles are medium to long, 1 to 2.5cm, with narrow bodies. They have large, rectangular-looking heads and long thread-like antennae that are beaded.
They also have two sets of wings; one set folds against its body and looks like body armor. Unlike other beetles, whose top wings are hard, these are soft and flexible.
They will also travel in large groups, and when disturbed during feeding, they will simply drop to the ground. It’s imperative any animals with you leave them alone, or they could get hurt.
Additionally, some people refer to them as stinging beetles though they do not have stingers.
How to Get Rid of Blister Beetles Naturally
Here are some natural and organic home remedies to eliminate these highly toxic and destructive pests, as well as their larvae, from your garden.
It’s best to wear gloves for this method. If you don’t grab it before it sees you, it will fall to the ground beneath the plants it’s feeding on or get lost in hay.
Make every effort to pick up the beetle from wherever it is and put it into a container or bucket filled with soapy water because they won’t be dead, only pretending to be.
Don’t squeeze it if you can help it else you could end up with cantharidin all over your gloves which, in turn, could transfer to bare skin.
Also, check your plants and handpick them off at least once a day, if not twice.
2. Diatomaceous Earth (DE)
This wonderful white powder is applied to the base of the host plants as well as around stones, and anywhere else you might think it would lay its eggs.
The silica in diatomaceous earth will tear up the underside of the beetle, killing it.
DE works like Sevin dust (only safer), keeping the beetles from laying their eggs on the soil where they would hatch and latch on to either ground bees or grasshoppers.
3. Oyster Lime Shell (OLS)
OLS is another natural powder, and this one is full of calcite. It won’t kill them as it’s more of a repellent, but it’s an excellent barrier for hindering them from laying their eggs.
Best when used before an infestation occurs. It also is good for enriching soil quality and raising its ph balance.
Many consider this as a chemical rather than a natural way to get rid of bad bugs in your garden. However, we included it on this list because that’s not the case.
Its ingredients break down and become inert in a couple of days after application. That’s because spinosad is derived through the fermentation process of a soil bacterium which makes it perfectly natural.
Spray this treatment directly on them during the heat of the day so as not to kill any bees. Besides, the product has to make direct contact with the bugs to work properly.
This is one of the best ways to get rid of blister beetles organically. Birds love beetles, and they’ll happily pick them off your plants all day long.
Attracting them is as simple as providing a source of water and an initial source of food until they discover the critters.
Certain plants and flowers like sunflowers and coneflowers will bring in the birds as well.
6. Row Covers
Row covers range anywhere from simple screens on frames to rolls of plastic sheeting stretched out over rows in the garden. Put them down right after planting but before the adults emerge from the pupa.
However, be sure to remove them when it’s time for pollinating. Having them down when the adults emerge will prevent them from feeding, and they will go elsewhere.
7. Weed Control
The black blister beetle loves weeds. They really like ironweed, pigweed, and ragweed. If you want to prevent them from lingering, get rid of the weeds in and around your vegetable garden.
Not just pull them either, you need to completely do away with them for the best results. Now that I’ve said that, there’s a caveat.
Some gardeners will keep pigweed around (trap crop) in the hopes the bugs will feed off of it and not on their crops.
8. Repel Grasshoppers
Blister beetle larvae make their meal out of grasshopper eggs, so getting rid of grasshoppers, preferably in a natural way, is highly effective in preventing an infestation of the little demons.
If you see a lot of grasshoppers in your garden or around the house, you most definitely will have these bad guys. A little research will tell you the best ways to get rid of grasshoppers.
If you want to keep away the critters without having to whip up DIY recipes, this is an excellent natural insecticide with its main active ingredient being an organic botanical.
Spray it directly on the bugs, but be careful not to soak the plant or the soil.
Bug Buster-O can be bought commercially. It is toxic to bees, so use with caution so as not to harm them.
10. Neem Oil
This lovely all-natural oil coats the body of the adult blister beetle and makes it sterile as well interfering with its biological need to feed. This will, eventually, get rid of the infestation.
Simply mix it in a ratio of 2 teaspoons (this brand) to one gallon of water with liquid soap like Castile. Shake well and spray directly on them.
If they fall off the plants, don’t assume they’re dead; they play possum.
Spray them until they are thoroughly coated, and don’t worry — over-spraying won’t hurt the host plants or the soil.
They have four larval stages and are known as Hypermetamorphic because of it. Other than that, they have four life stages just like other beetles: egg, larvae, pupa, and adult.
Eggs – they lay the eggs in the soil, under rocks, or on the host plant.
Larvae go through four basic stages; however, they can degenerate back or jump completely over any of the stages depending on their living conditions. They are in this stage during the winter months.
- Triungulin – the larvae have fully formed legs they use to take them to and attach themselves to bees or grasshoppers. These, in turn, will take them back to their hives or egg nest where the larva will feed on the occupants.
- Scarabaeiform – first grub stage — most of the growth takes place here
- Coarctate – the grub can become emaciated and puny with very low body function, depending on its living conditions, and it can remain alive in this state for up to 230 days if need be
- Scarabaeiform – second grub phase — recovers from the Coarctate stage and grows some more before creating its cocoon.
Pupa – remains in this stage for two weeks
Adult – emerges in early spring
Blister Beetles prefer to eat the flowery parts of plants, but they will eat the leaves if they have to. They will eat the leaves to skeleton form.
They eat the pollen and swallow the nectar of flowering plants like sunflowers, chrysanthemum, aster, dahlia, legumes, and members of the nightshade family up to and including tomato, potato, and eggplant.
Due to them eating nectar and pollen, the plants aren’t able to be pollinated or develop like they’re supposed to. This means they won’t produce vegetables or seeds.
In addition to ruining the crops in a garden, they also cause damage to livestock. When animals accidentally eat the beetles that are in their hay, they get sick, and they could die.
This is from the damage the cantharidin does to their digestive and urinary tracts. Even animals the size of horses can die from eating as little as five of these bugs.
Types of Blister Beetles
Found in the family of Meloidae, there are about 2500 species of Blister Beetle found in the world, and they are divided into four subfamilies .
The US is home to two of these subfamilies: Meloinae and Tetraonycinae. They come in a variety of colors — striped, ash gray, black, and one is even metallic green.
The other two subfamilies are: Eleticinae found mostly in Eastern Asia and parts of Africa, and Nemognathinaem found in Australia. Both of these subfamilies have bright colors and they are very common.
Blister Beetles are very prolific when breeding, and they like to travel in crowds. This means you’ll have a major infestation before you’re even aware there’s an issue.
By implementing the various prevention methods, you will lower your chances of providing the extremely toxic and destructive blister beetles with a home.
If, however, you do find the little demons in your garden or feed hay, the best natural control methods for repelling and killing them are also on the list.
Some of these methods are quite effective when used alone. Others, used in conjunction with some of the others, have done quite a bit towards keeping them out of the garden and feeding hay.
It all depends on how much work you are willing to do before, during, and after there’s a noticeable infestation.