Blister beetles
Long, narrow, soft-bodied beetles that swarm over leaves and flowers, and release a chemical that causes painful blisters on skin.
Also known as: Epicauta beetles
Symptoms and identification
Leaves and flowers are chewed in patches and can be stripped quickly by groups of beetles. The beetles are slim, 1 to 2 cm long, and black, grey, striped or metallic, with a narrow neck and soft wing covers.
Causes
Adults feed on foliage and flowers in summer, often in swarms, while the young feed on grasshopper eggs in the soil. Numbers vary from year to year and are higher where grasshoppers are common.
Organic treatment
Wear gloves and long sleeves, and brush beetles into a bucket of soapy water. Do not crush them on skin, as they release cantharidin, which blisters skin and is poisonous to horses and other animals.
Prevention
Check plants in midsummer, and keep weeds under control, since many beetles breed in and move from them. Cover small plants with fine mesh.
Chemical treatment (use with care)
Use an insecticide labelled for blister beetles on that crop, following the label.