Blister Beetle Infestation in a Garden

Mylabris pustulata (arian.suresh via Wikimedia Commons, CC BY 2.0)

Blister beetles are a common pest in gardens and agricultural fields, causing damage to crops and ornamental plants. They belong to the family Meloidae and are known for their ability to secrete a toxic chemical called cantharidin. This chemical not only causes skin irritation and blistering in humans and animals, but also makes the beetles unpalatable to predators. Blister beetles feed on leaves, stems, flowers, and even fruit of various plants, and their feeding can result in significant defoliation and plant damage.

Blister beetles are often attracted to gardens and agricultural fields during the warmer months, when they are in the adult stage of their life cycle. They can be found on a variety of plants, including vegetables, fruits, ornamental flowers, and shrubs. In addition to causing direct damage to plants, blister beetles can also serve as vectors for plant diseases, making their control and management a priority for gardeners and farmers.


  • Leaves and flowers with holes or ragged edges from feeding
  • Significant defoliation of plants, leading to stunted growth or even plant death
  • Irregularly shaped or missing plant parts, as blister beetles feed on the entire plant including stems, leaves, and flowers
  • Presence of adult beetles on plants or in the soil, as they are often seen on the plant during feeding or resting
  • Wilted or discolored plants, as blister beetles can introduce toxins into the plant that can affect its growth and health
  • A sticky or gummy substance on plants or in the soil, as blister beetles release a chemical called cantharidin when they are disturbed, which can cause skin irritation and blistering in humans and animals.

It is important to regularly inspect plants and the surrounding soil for signs of blister beetle infestations, and to take action promptly to prevent further damage.

What is a Blister Beetle

Blister beetles can be easily identified by their unique appearance, and it is important to be familiar with their characteristics to prevent infestations and protect plants in the garden.

  • Typically 1/2 to 1 inch in length, with a range from 6-25mm
  • Oval or oblong in shape, with a somewhat flattened body
  • Wide range of colors, including black, gray, striped, and brightly colored in shades of red, yellow, or metallic green
  • A distinguishing feature is the elongated head and narrow neck, which sets it apart from other beetles in the same family
  • Some species of blister beetles have a pronounced thorax with distinct markings, while others are uniform in color
  • They have six legs, two antennae, and prominent eyes that are usually large and round

Treating a Blister Beetle Infestation

To prevent blister beetle infestations, it is important to maintain a clean and well-manicured garden, removing weeds and debris from around the area. Monitoring for adult beetles on plants and in the soil, and taking prompt action to control infestations can help reduce the damage caused by these pests. It may be necessary to use a combination of methods to effectively control blister beetle infestations in a garden. Cultural practices, such as crop rotation and companion planting, as well as chemical control methods, can be used to manage blister beetle populations and protect plants in the garden.

Cultural Control

  • Remove weeds and debris from around the garden: Weeds and debris provide habitat for blister beetles and can serve as a source of food and shelter. Removing these areas can help reduce the population of blister beetles in the garden.
  • Monitor for adult beetles on plants and in the soil: Regularly inspecting plants and surrounding soil for adult beetles can help identify infestations early and prevent further damage.
  • Crop rotation: Blister beetles lay their eggs in the soil, and rotating crops can prevent the beetles from laying eggs in the same area year after year.
  • Companion planting: Planting certain plants, such as dill, fennel, or tansy, that are less attractive to blister beetles can help reduce their populations in the garden.
  • Maintaining a clean and well-manicured garden: Keeping the garden free of weeds and debris, and maintaining healthy and vigorous plants, can help reduce the attraction of the garden to blister beetles.

Physical Control

  • Hand picking and removing adult beetles from plants: This method can be effective in small gardens or for early detection of infestations. Simply remove the beetles by hand and dispose of them in a sealed bag or container.
  • Using sticky traps: Placing sticky traps near infested plants can help capture adult beetles and reduce their populations.
  • Vacuuming beetles from the soil and plant surfaces: This method is useful for removing beetles from the soil and hard-to-reach places on plants. Vacuum the beetles and dispose of them in a sealed bag or container.
  • Covering plants with protective covers or screens: Covering plants with protective covers or screens can prevent beetles from accessing the plants and feeding on them.

Chemical Control

  • Using insecticides to kill adult beetles and larvae: Insecticides, such as carbaryl, pyrethroids, or spinosad, can be applied to the plants and surrounding soil to kill adult beetles and larvae.
  • Treating plants and soil with insecticides to prevent eggs from hatching: Preventive treatments with insecticides can be applied to the soil and plants to prevent eggs from hatching and emerging as larvae.
  • Using botanical insecticides, such as neem oil or pyrethrin: These natural insecticides can be used to control blister beetles without the use of synthetic chemicals.

Biological Control

  • Encouraging the presence of natural predators: Encouraging the presence of birds and beneficial insects, such as ladybugs, lacewings, and parasitic wasps, can help control blister beetle populations by feeding on them.
  • Using parasitic wasps: Parasitic wasps, such as Tetrastichus julis, can be introduced into the garden to control blister beetle populations by laying their eggs in blister beetle eggs or larvae.
  • Using fungal pathogens: Fungal pathogens, such as Beauveria bassiana, can be used to infect and kill blister beetles by targeting the larvae in the soil.