Identification: Blister beetles have elongated, narrow bodies and can be black, brown, striped, or metallic green in color.
The larvae overwinter in the soil and emerge in spring to feed. Adults are active in midsummer. There are typically one or two generations each growing season, depending on your region. Blister beetles are found throughout North America.
Damage: These long-bodied beetles feed on leaves and flowers of garden crops such as tomatoes, potatoes, melons, carrots, cabbage, peas, squash and eggplants. When they’re present in force, they can defoliate plants entirely. But blister beetle larvae are gardener’s helpers, because they dine on the eggs of a different garden pest — grasshoppers.
Control: Options for control/elimination include:
- Mow grasses before they flower. These flowers attract adult blister beetles.
- Because of the beneficial role that blister beetle larvae play, it’s best to leave small infestations of adult blister beetles alone. If you’re concerned that beetle populations are increasing, don a pair of garden gloves (when crushed, blister beetles exude a substance that can burn your skin) and handpick the adults. Drop them into a bucket of soapy water. Picking is easiest in the morning when the beetles are sluggish.
- In midsummer, cover plants with insect netting to prevent beetles from feeding.
- Rose Rx 3-in-1 Wards off spider mites, whiteflies, lily beetles and Japanese beetles. Also controls black spot and powdery mildew. It works for all flowers and ornamentals; safe for houseplants and food crops, too.
- Summerweight Garden Fabric Fabric cover screens out Japanese beetles, potato beetles, cabbage worms, leaf miners, carrot flies and most vine borers. Transmits 85 percent of the light to plants without allowing heat build-up.
- Insect Pop-Up Nets Protect your crops from insects with this net, designed to fit on a raised bed.
- All Seasons Spray Oil Unlike heavy “dormant” spray oils that can only be used in early spring, this lightweight oil can be used year-round on vegetables and ornamental plants to control many insect pests, including aphids, mealybugs, red spider mites and scale.