Your Guide: How To Get Rid Of Blister Beetles In Garden

Blister beetles can quickly cause damage in your garden. They show up in groups and eat plants fast. These beetles also carry a harmful chemical called cantharidin. This chemical can cause painful blisters on your skin if you touch the beetles. It is also very bad, even deadly, for animals like horses if they eat hay with dead beetles in it. Getting rid of blister beetles needs quick action to save your plants and stay safe.

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What Blister Beetles Look Like

Knowing what blister beetles look like helps you find them early. This helps stop problems before they get big.

Here is what to look for:

• Shape: They have long, narrow bodies. Their heads are wider than their bodies right behind the head. This makes them look a bit like they have a neck.
• Size: They are usually about 1/2 inch to 1 inch long.
• Colors: They come in many colors. Some are solid gray, black, or brown. Others have stripes of gray and black. Some look shiny blue, green, or even black with yellow edges. Different kinds live in different places.
• Hard Wings: Their hard outer wings (elytra) are soft and bending. They are not stiff like the wings of many other beetles. The wings do not fully cover the sides of their body.

You often see them walking slowly over plants or eating flowers and leaves. Learning what they look like is the first step in identifying blister beetles.

Signs Blister Beetles Are Eating Your Plants

Blister beetles eat leaves and flowers very quickly. They often feed in groups. When they eat, they can strip a plant down to just the tough parts of the leaves. This looks different from how other bugs eat.

Look for these blister beetle damage symptoms:

• Ragged Holes: They chew big, uneven holes in leaves.
• Leaf Edges Gone: They often eat the edges of leaves first.
• Flowers Destroyed: They love to eat flower petals and pollen. They can ruin flowers fast.
• Skeletonizing: In some cases, they eat all the soft parts of the leaf, leaving just the veins. This makes the leaf look like a skeleton.
• Plants Die Back: If many beetles feed on a small plant, they can kill it. Larger plants can look very thin and weak after a visit from these beetles.
• Sudden Damage: The damage often appears very quickly, sometimes overnight, especially if a group of beetles arrives.

Finding these signs means you likely have blister beetles. You need to act fast.

Learning About Blister Beetle Life Stages

To control blister beetles well, it helps to know their life story. The blister beetle life cycle stages are different from many other bugs. This difference is important for how we fight them.

Blister beetles have what is called complete metamorphosis. This means they go through four main stages: egg, larva, pupa, and adult. But their larval stage is special. It has several forms. This is called hypermetamorphosis.

Let’s look at the stages:

• Egg: Female beetles lay groups of eggs in the soil. This often happens near the base of plants. They might lay hundreds of eggs.
• Larva (Special Stages): This is the most complex part.
  • First Stage (Triungulin): The tiny larvae that hatch from eggs are called triungulins. They are active and have legs. They move around to find food. For many kinds of blister beetles, this food is grasshopper eggs. The triungulins dig into the soil to find grasshopper egg pods. This is actually helpful for us because they eat a garden pest!
  • Later Stages: Once the triungulin finds a grasshopper egg pod, it eats and grows. It changes form several times. It loses its legs and becomes a soft, grub-like larva. It eats the grasshopper eggs.
  • Pupa-like Stage: After eating enough, the larva enters a stage that looks like a pupa but can sometimes still move a little. It stays in the soil.
  • Another Larva Stage: Sometimes, the beetle can go back to an active larva stage if conditions are not right.
• Pupa: After the special larval stages, the beetle becomes a true pupa in the soil. In this stage, it changes into the adult form.
• Adult: The adult beetle comes out of the soil, usually in summer. This is the stage that eats your garden plants. This is the stage you see and need to control.

Knowing they spend most of their life cycle hidden in the soil, often eating grasshopper eggs, changes how you think about control. It means focusing on the adult beetles when they appear on your plants.

What Plants Do Blister Beetles Eat?

Blister beetles are not picky eaters, but they do have favorites. Knowing their common blister beetle host plants helps you watch these plants closely.

They often like:

• Vegetables:
  • Potatoes (a major favorite)
  • Tomatoes
  • Eggplants
  • Peppers
  • Beans
  • Peas
  • Corn
  • Alfalfa (a big problem for hay fields)
• Flowers:
  • Asters
  • Chrysanthemums
  • Zinnias
  • Dahlias
  • Other composite flowers (flowers with many small petals like daisies)
• Other Plants:
  • Some weeds
  • Various garden plants

They tend to gather on these plants and eat them down fast. If you grow these plants, be ready to check them often for signs of beetles.

Why Blister Beetles Are Risky: Cantharidin

As mentioned, blister beetles are not just plant pests. They are also dangerous because they carry a poison called cantharidin. This is how they get their name – they cause blisters.

Here is what to know about cantharidin poisoning blister beetles:

• What it is: Cantharidin is a strong chemical. The beetles make it for defense. It is in their blood (hemolymph).
• How you get exposed:
  • Touching: If you squash a blister beetle on your skin, the cantharidin can cause red, painful blisters. This happens within hours.
  • Eating: If the beetles are eaten, the poison is much more dangerous.
• Danger to Animals: Cantharidin is a big problem in hay. If alfalfa or other hay is cut and dried with blister beetles in it, the cantharidin stays active. Horses are very sensitive to it. Eating even a few dozen beetles can make a horse very sick or even kill them. Other animals can also be affected, but horses are most at risk.
• Danger to People: It is very unlikely a person would eat enough beetles to be seriously harmed. The main risk to people is skin blistering from contact. However, cantharidin is toxic if swallowed.

Because of the risk of cantharidin poisoning blister beetles, you must be careful when handling them. Do not touch them with bare hands. Wear gloves. Also, be careful about them getting into animal feed.

How to Get Rid of Blister Beetles

Getting rid of blister beetles often needs a mix of methods. Since they appear quickly and eat fast, you need to be ready.

Steps for Stopping Blister Beetle Problems

Taking steps early can help a lot. Preventing blister beetle damage is easier than dealing with a big group eating your plants.

• Check Plants Often: Look at your plants daily, especially favorite host plants, starting in early summer. Check leaves and flowers. Finding just a few beetles lets you stop them before they lay eggs or a large group arrives.
• Manage Weeds: Some blister beetles eat weeds. Keeping weeds down in and around your garden can make it less attractive to them.
• Cut Hay Carefully: If you grow hay (especially alfalfa), cut it carefully to avoid crushing beetles. Use equipment that has a crimper/conditioner turned off. Avoid driving over cut hay. Harvest before the beetles are most active (late morning/afternoon).
• Check Hay: If you buy hay, check it for dead beetles. They look like dark specks among the hay stalks.
• Grow Different Plants: Planting a mix of plants instead of large areas of just one type can help. This makes it harder for pests that like only one kind of plant.

These steps can lower the chance of a big problem.

Removing Blister Beetles By Hand

One simple way to get rid of a few beetles is to pick them off the plants. This is called handpicking blister beetles.

It is important to do this safely because of cantharidin.

Here are the steps:

1. Wear Gloves: Always wear thick garden gloves. Do not touch the beetles with bare skin.
2. Use a Container: Hold a jar or bucket with soapy water under the beetle.
3. Knock Them In: Gently tap the plant part the beetle is on. The beetle should fall into the soapy water. The soap helps break down the cantharidin and kills the beetles.
4. Check All Plants: Walk around your garden and check all affected plants. Blister beetles often group together, so you might find many on one plant.
5. Seal and Dispose: Once you have collected the beetles, seal the container. Dispose of the dead beetles safely. Do not leave them where pets or other animals can find them. Pouring the soapy water down a drain or burying the sealed container is best.
6. Clean Up: Wash your gloves and hands well after you are done.

Handpicking works best when you find the beetles early and there are not too many. It needs you to check your garden often.

Using Methods That Are Natural and Organic

Many gardeners prefer to use methods that do not involve strong chemicals. There are organic methods blister beetles that can help.

• Row Covers: You can put fine mesh row covers over your plants. This is a barrier that stops the beetles from landing on the plants to eat. Put them on as soon as plants come up or are planted. Make sure the edges are sealed well so beetles cannot crawl under. This works best for plants like beans, peppers, and eggplants when they are young.
• Sticky Traps: Some gardeners use yellow sticky traps near plants. Blister beetles are attracted to yellow. While traps can catch some beetles, they also catch helpful insects. Use them with care and know they might not catch all the beetles.
• Diatomaceous Earth (DE): This is a fine powder made from tiny fossil shells. It feels soft to us but is sharp to insects. If beetles crawl through it, it cuts their outer layer, and they dry out and die. Apply food-grade DE to plants and the soil around them. It needs to be dry to work. Reapply after rain. Wear a mask when applying it so you don’t breathe it in. DE can also harm helpful insects, so use it carefully.
• Neem Oil: Neem oil is a natural plant oil. It can stop insects from feeding and mess up their growth. Spray neem oil on plants where you see beetles. It works best on young beetles, but can affect adults too. Apply it late in the day to protect bees. Follow label directions carefully.

These organic methods can help reduce blister beetle numbers without harsh chemicals. They are often part of a bigger plan to control pests.

Using Nature’s Help: Natural Predators

Nature has ways to help control pests. Finding out about natural predators blister beetles can be useful. However, blister beetles are not a favorite food for many animals because of the cantharidin poison.

• Birds: Some birds might eat blister beetles, but they might also learn that the beetles taste bad or make them sick. Their impact is likely small.
• Other Insects: Remember the larval stage of some blister beetles eats grasshopper eggs? This shows part of their life helps control another pest. But other insects are not known to be major predators of adult blister beetles. The cantharidin protects them.
• Praying Mantises, Assassin Bugs: While these bugs eat many insects, they may avoid blister beetles because of the poison.

Building a healthy garden environment that brings in helpful insects is always good. But do not rely on natural predators as your main way to control adult blister beetles because of their cantharidin defense.

Using Sprays to Kill Blister Beetles

Sometimes, if you have a very large group of blister beetles eating your plants fast, you might need to use insecticides for blister beetles. This should often be the last choice, especially in a home garden.

If you choose to use a spray, follow these important rules:

• Identify Correctly: Make sure you really have blister beetles before you spray.
• Choose the Right Product: Look for products that list blister beetles on the label. Common active ingredients include:
  • Pyrethrins: These are natural plant extracts or synthetic versions (pyrethroids like permethrin, bifenthrin). They kill insects quickly when sprayed directly on them. They break down relatively fast.
  • Carbaryl (Sevin): This is an older chemical insecticide. It kills a wide range of insects, including blister beetles.
  • Spinosad: This is a natural product made by soil bacteria. It is toxic to insects that eat it or touch it. It is often allowed in organic gardening under certain rules, but it still kills insects and can harm bees if used wrong.
• Read the Label: ALWAYS read the full label before using any insecticide. The label tells you:
  • What pests it kills.
  • What plants you can use it on.
  • How much to use.
  • How to mix it.
  • How to apply it safely.
  • When to apply it (time of day).
  • How long you must wait after spraying before you can harvest (Pre-Harvest Interval or PHI).
• Apply Safely:
  • Wear long sleeves, pants, gloves, and maybe eye protection or a mask.
  • Spray when there is no wind.
  • Spray in the late evening when bees are not active on the plants. Blister beetles are often active during the day.
  • Spray only the plants where you see the beetles. Do not spray flowers that are important for pollinators if possible.
  • Do not spray near water.
• Check Results: See if the spray worked. You might need to reapply if more beetles show up, following label directions.
• Consider Impact: Remember that insecticides can kill helpful insects too. Use them only when needed and target them carefully.

Using insecticides is a quick way to kill beetles, but it comes with risks to helpful bugs, water, and yourself.

Using Different Methods Together

The best way to handle blister beetles and other garden pests is often to use a mix of different methods. This is called Integrated Pest Management (IPM).

An IPM approach for blister beetles could look like this:

1. Watch Closely: Start by checking your plants often for signs of beetles or damage (prevention, identifying, damage symptoms). This is the first step.
2. Remove By Hand: If you see a few beetles, safely handpick them (handpicking).
3. Use Barriers: For certain plants, use row covers early on (organic methods, prevention).
4. Improve Garden Health: Keep weeds down (prevention, host plants). Encourage helpful insects, even if they don’t eat adult blister beetles, to keep the whole garden healthy (natural predators in general garden health).
5. Consider Sprays If Needed: If a sudden large group of beetles appears and is quickly destroying plants, and other methods are not enough, you might decide to use a targeted insecticide as a last resort (insecticides). Use it safely and follow directions strictly.

Using IPM means you are not just reacting to pests with one tool (like spraying). You are watching, planning, and using different methods to keep the beetles down while causing the least harm to your garden and helpful insects.

Keeping Yourself Safe

Dealing with blister beetles means being careful because of the cantharidin.

• Always wear gloves when working with plants that might have blister beetles, especially if you are removing them by hand.
• If you think you have crushed a beetle on your skin, wash the area right away with soap and water. Watch for blisters. If a large blister forms or it looks infected, see a doctor.
• If you use insecticides, follow all safety steps on the label. Wash clothes worn during spraying separately.

Safety for yourself and your animals is very important when dealing with blister beetles.

Putting It All Together

Blister beetles can be a real problem in the garden because they eat plants fast and have a dangerous toxin. But you can manage them.

Start by knowing what they look like and the signs they leave on plants. Understand their life cycle to know when you might see the adults. Know which plants they like to eat so you can check those first. Always remember the danger of cantharidin and handle beetles with care.

To get rid of them or stop them from coming, use a mix of methods. Check plants often. Remove beetles by hand when you see them, always wearing gloves. Use row covers on young plants to keep beetles off. Keep your garden clean. If you must use a spray, choose the right one, read the label carefully, and spray safely in the evening to protect bees.

By being watchful and using different safe methods, you can protect your garden from blister beetles and avoid their harmful effects.

Frequently Asked Questions About Blister Beetles

Here are some common questions people ask about blister beetles.

h4 What time of year are blister beetles a problem?

Adult blister beetles are usually seen in summer, often from late spring through early fall. This is when they come out of the soil after becoming adults and start feeding on plants. The exact time can change based on where you live and the weather.

h4 If I see one blister beetle, does that mean I have a big problem?

Not always. Seeing one might just mean they are starting to appear. But because they often feed in groups and can show up quickly, seeing one is a sign to start watching your plants closely and be ready to take action if you see more.

h4 Can blister beetles hurt my pets?

Yes, especially if your pet (like a dog) eats them. The cantharidin can make them very sick. Keep pets away from areas where you are dealing with blister beetles or where dead beetles might be. The biggest risk is to horses eating hay with dead beetles in it.

h4 How long do blister beetle blisters last on skin?

If you get cantharidin on your skin, a blister usually forms within a few hours. The blister can be painful and might last for several days or even a week or more before it heals. It’s important to wash the area right away and avoid breaking the blister if possible to prevent infection.

h4 Will praying mantises eat blister beetles?

While praying mantises eat many insects, they might avoid blister beetles. The cantharidin in blister beetles protects them from many predators, including some insects that would normally eat other beetles. So, you cannot rely on praying mantises to control a blister beetle problem.

h4 Are there different kinds of blister beetles?

Yes, there are many different species of blister beetles. They vary in color, size, and where they live. Some common ones include the striped blister beetle, the ashgray blister beetle, and the black blister beetle. They all carry cantharidin and can harm plants.

h4 Is Diatomaceous Earth safe to use?

Food-grade diatomaceous earth is considered safe to use in gardens. However, it is a fine dust. You should wear a mask when applying it to avoid breathing it in. It can also harm beneficial insects if they come into contact with it, so use it only where needed.

h4 How quickly do blister beetles eat plants?

Blister beetles are known for eating very fast, especially when they are in groups. A large group can severely damage or even strip plants in just a day or two. This is why finding them early and acting quickly is important.

h4 If I use an insecticide, will it get rid of the blister beetles for the whole season?

Maybe, but not always. An insecticide will kill the beetles that are on the plant when you spray. However, more beetles might fly into your garden later from other areas. You need to keep watching your plants and be ready to treat again if needed, following the product label for how often you can spray.

h4 Do blister beetles come back year after year in the same garden?

Yes, if the conditions are right. Adult beetles lay eggs in the soil in or near your garden. If there are grasshopper eggs for the larvae to eat, new adult beetles can emerge from the soil in the same area the following year. Using methods like checking plants early each summer can help manage this.

h4 Can I just leave the beetles alone?

Leaving blister beetles alone is not a good idea, especially if you have many of them. They will quickly eat your plants, causing serious damage. Also, they are a risk because of the cantharidin, which can harm you or animals if you come into contact with them. It’s best to take steps to remove them safely.

h4 Will rain wash away insecticides for blister beetles?

Most insecticides need time to dry after spraying to work well. Rain shortly after spraying can wash away the product, making it less effective. Check the product label; it often says how long the spray needs before it is rainfast. If it rains soon after, you might need to spray again later, but be sure to follow the label rules for reapplication times.