Blister Beetle
A long, narrow beetle with a big head and a skinny neck, often striped gray and yellow or plain black. They arrive in swarms in late summer, chew leaves from the edges in, and can leave nothing but stems in a day or two.
Pest checklist
Four things to look for. If most of them match what you are holding, you are in the right place.
What gets rid of them
Gentlest option first. For most backyard cases the first one is enough, so try these in order and stop as soon as it works. If you do spray something, the product label tells you how — please read the notice further down.
1Knock them into soapy water
Wear gloves. Hold a bucket under the plant and sweep the beetles in with a stick or gloved hand rather than crushing them on the plant.
nitrile garden glovesTry this first2Cover the bed
Row cover over greens and chard in August and September keeps a swarm from landing on them at all.
floating row cover garden fabric3Deal with grasshoppers
Blister beetle grubs live on grasshopper eggs, so a heavy grasshopper year usually means a heavy blister beetle year the next one.
4Spray if the swarm is large
A spinosad or pyrethrin product labeled for the crop will knock them down. Check the days-to-harvest interval before spraying anything you are about to pick.
spinosad garden insect spray
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Which plants get blister beetle
Every plant we cover that gets blister beetle, grouped by type — tap any one to open its page. A note beside a plant came from that plant’s own entry, because the same pest can be a minor nuisance on one plant and a serious problem on another. Plenty of plants we do not cover get it too.
perennial1
Plant families hit hardest
Related plants often share the same problems, so if one plant in a family has it, check the others. The largest group here is Amaranthaceae, with 3 of the 10 affected plants.
- Amaranthaceae3 plants
- Solanaceae3 plants
- Brassicaceae2 plants
When to treat
Act the same day you find a swarm, and wear gloves: these beetles contain a chemical called cantharidin that blisters skin and is poisonous to eat, and it stays active in the dead beetles.
Timing only — the label is the law
This page tells you when to watch for blister beetle and when treating is worth considering. It is not a recommendation to apply any particular product. Read and follow the product label before you spray — under federal law the label is the legal instruction, and using a pesticide against it is illegal.
- Check the pre-harvest interval. Every product that’s cleared for an edible crop sets a minimum number of days between spraying and picking. Find it on the label before you spray anything you intend to eat.
- Check the re-entry interval before you or anyone else works in the treated area again, and use the protective equipment the label names.
- Confirm the product is registered for your crop in your state. This page groups many different crops together, and a product legal on one of them is not legal on all of them — state registrations differ too. Your state pesticide agency or local extension office can confirm both.
- Rates and mixing instructions come from the label, never from us. We don’t publish them because they differ by product and formulation.
Other problems on the same plants
If a plant gets blister beetle, these are the problems it most often gets as well, so they are worth checking for while you are out there. They tend to appear together; one does not cause another.