Squash Bug Infestation in a Garden

Squash bug nymphs (Pollinator via English Wikipedia, CC BY-SA 3.0)

Squash bug infestations can be a significant problem for gardeners who grow squash and related plants, such as pumpkins, zucchinis, and cucumbers. These pests feed on the sap of the plants, causing damage that can result in wilting, yellowing, stunted growth, and death of the affected plant. Squash bugs can also cause soft, water-soaked spots on the fruit that can become moldy and rot, rendering the fruit inedible.


  • Wilting or yellowing of leaves, starting at the bottom of the plant and gradually spreading upward
  • Discoloration and eventual death of leaves, causing leaves to become dry and brittle
  • Stunted plant growth, with reduced size and vigor of the plant
  • Brown or black discoloration on stems, caused by the bugs sucking sap from the plant
  • Soft, water-soaked spots on fruit, which can become moldy and rot, rendering the fruit inedible
  • Presence of eggs, nymphs, and adult squash bugs on the plant, often found on the undersides of leaves and near the stem.

Note: In addition to the above symptoms, it’s also possible for the plant to become infected with fungal or bacterial diseases as a result of the feeding damage caused by the squash bugs.

What is a Squash Bug

Squash bugs are persistent pests that can be difficult to control, as they have a long life cycle and are able to reproduce quickly. They overwinter as adults, hiding in leaf litter and other debris, and emerge in the spring to lay eggs on the undersides of leaves. The eggs hatch into nymphs, which feed on the sap of the plants and grow into adult bugs. This cycle can repeat several times in a growing season, leading to heavy infestations that can cause significant crop loss.

Treating a Squash Bug Infestation

Preventing and controlling squash bug infestations requires a multi-pronged approach that includes monitoring for the presence of eggs and nymphs, removing and destroying infested leaves and debris, and using appropriate insecticides. Early detection and quick action are key to preventing the spread of these pests and protecting the health of your garden.

It may be necessary to use multiple methods to effectively control squash bug infestations in a garden. For example, using a combination of cultural control practices, physical control methods, chemical control measures, and biological control strategies can provide the most comprehensive protection.

Cultural Control

  • Remove and destroy infested leaves and debris regularly, including any fallen leaves or plant material around the base of the plants. This will help to reduce the number of overwintering squash bugs and disrupt the life cycle of the pest.
  • Keep the garden clean and free of plant debris, as this is where the squash bugs will overwinter. This can be done by removing leaves, stems, and other plant material from the garden and disposing of it in a sealed bag or composting it.
  • Rotate crops to reduce the risk of repeated infestations. This means planting different crops in the same area each year, so that the pests do not have a continuous food source.
  • Maintain healthy, vigorous plants by providing adequate water and nutrients. This will help the plants to better withstand the feeding damage caused by the squash bugs.

Physical Control

  • Handpick adult squash bugs and nymphs from the plants and drop them into a bucket of soapy water to kill them. This is an effective method for small infestations, but may not be practical for large gardens or heavy infestations.
  • Place sticky barriers around the base of the plants to prevent the bugs from reaching the stems and leaves. This can be done by wrapping the stems with sticky tape, such as Tanglefoot, or by placing a shallow dish filled with soapy water around the base of the plant.
  • Use floating row covers to protect the plants from infestations. This involves covering the plants with a light-weight, permeable fabric that allows sunlight and water to penetrate, but keeps the bugs out. The covers should be removed when the plants start to flower to allow for pollination.

Chemical Control

  • Apply insecticidal soap or neem oil to the plants, paying special attention to the undersides of the leaves where the eggs and nymphs are most likely to be found. These products work by smothering the bugs and disrupting their ability to feed. They are generally safe for the environment and beneficial insects, but should be applied according to the label instructions.
  • Use a systemic insecticide that is taken up by the plant and provides long-lasting protection. These products work by spreading through the plant, killing the bugs as they feed. Some common systemic insecticides include imidacloprid and dinotefuran.

Biological Control

  • Encourage populations of beneficial insects, such as ladybugs and lacewings, that feed on the nymphs and eggs of squash bugs. This can be done by planting a variety of flowers that provide nectar and pollen for the beneficial insects, and avoiding the use of broad-spectrum insecticides that can harm these insects.
  • Introduce natural predators, such as the parasitic wasp Trichopoda pennipes, which lays its eggs on adult squash bugs. These wasps can be purchased from a supplier and released into the garden.
  • Use a biological insecticide, such as Bacillus thuringiensis, which is toxic to the larvae of squash bugs and other pests. This product is a bacteria that is toxic to the pests but safe for humans and other animals.