How to Get Rid of Blister Beetles
A long, soft-bodied beetle with a narrow neck that feeds on flowers and vegetable foliage. Its body contains cantharidin, a chemical that raises blisters on skin. If you are seeing them in gardens and on plants, the steps below will help you clear them out and keep them from coming back.
Quick answer
- Knock beetles into soapy water with a gloved hand instead of crushing them
- Keep weeds, especially pigweed, cut back around the garden
- Cover susceptible crops with row covers during midsummer
Handling or crushing blister beetles can cause painful skin blisters, and hay contaminated with them can poison horses.
Confirm you have blister beetles
Start by confirming the bug. Blister Beetles have a few features that set them apart. Adults measure 8–25 mm (up to about 0.98 in) and are usually black, gray and orange. Look for these features:
- Long, soft, cylindrical body with flexible wing covers
- Head wider than the narrow neck behind it
- Often black, gray or striped orange and black
They are most often confused with firefly. See the full blister beetle profile for side-by-side details.
Why you have blister beetles
Blister Beetles are drawn to the specific plants they feed on and multiply quickly in warm weather. Planting the same crop in the same bed each year makes outbreaks worse. Broad-spectrum sprays can kill the predators that would otherwise keep them in check. They are most active in summer, so expect to see more of them then.
When you'll see blister beetles
Blister Beetles are most active in summer. Summer heat speeds up development, so populations can grow quickly.
Typical places to check: garden or plants.
Step-by-step: getting rid of blister beetles
Step 1: Knock beetles into soapy water with a gloved hand instead of crushing them
Knock beetles into soapy water with a gloved hand instead of crushing them. Combine this with the other steps rather than relying on it alone.
Step 2: Keep weeds
Keep weeds, especially pigweed, cut back around the garden. Combine this with the other steps rather than relying on it alone.
Step 3: Cover susceptible crops with row covers during midsummer
Cover susceptible crops with row covers during midsummer. Repeat this for at least two to three weeks, since eggs and hidden insects keep appearing for a while.
Natural and low-toxicity options
These methods work well alongside the steps above and keep chemical use to a minimum:
- Hand-pick pests or knock them into a bucket of soapy water.
- Use floating row covers as a physical barrier.
- Attract beneficial insects with flowering herbs such as dill, yarrow and alyssum.
- Try insecticidal soap, neem oil or Bt products labeled for this pest, following the label.
If you do use a pesticide, choose one labeled for this pest and the place you're treating, and follow the label exactly. The label is the law.
When to call a professional
Most home gardens can handle blister beetles without a professional. Contact your local cooperative extension office if damage is severe or you can't confirm the pest.
How to keep blister beetles from coming back
- Rotate crops and clean up plant debris at the end of the season.
- Inspect plants weekly, especially leaf undersides.
- Keep plants healthy with proper watering and spacing.
- Encourage birds, ladybugs, lacewings and parasitic wasps.
Safety notes
Handling or crushing blister beetles can cause painful skin blisters, and hay contaminated with them can poison horses.
Call 911 right away if someone has trouble breathing, swelling of the face or throat, dizziness or a racing heartbeat after a bite or sting.
About beetles
The blister beetle is one of the beetles. Beetles go through complete metamorphosis: egg, larva (grub), pupa and adult. The larval stage often does the most feeding and damage, and it can last from a few weeks to several years depending on the species. Adults protect their flight wings under hard wing covers called elytra, which is why most beetles look armored and meet in a neat line down the back.
Look closely at larvae as well as adults. Grubs in soil, fuzzy larvae in closets and small worms in flour are all beetle larvae, and finding them tells you where the problem is centered.
Frequently asked questions
What is the fastest way to get rid of blister beetles?
Knock beetles into soapy water with a gloved hand instead of crushing them. Most people see a clear drop in activity within one to three weeks when they combine this with sealing entry points and removing whatever attracts them.
Are blister beetles dangerous?
Handling or crushing blister beetles can cause painful skin blisters, and hay contaminated with them can poison horses.
When are blister beetles most active?
Blister Beetles are most active in summer.
What do blister beetles look like?
Long, soft, cylindrical body with flexible wing covers. Adults measure 8–25 mm (up to about 0.98 in).