Thrip Infestation in a Garden

Thrips, eggs, and nymphs (via Wikimedia Commons, CC BY 2.0)

Thrips are tiny, slender insects that can infest gardens and cause significant damage to plants. They feed on the sap of leaves and flowers, causing discoloration, distortion, and reduced growth. In severe cases, thrip infestations can lead to plant death.


  • Discoloration or silver-colored streaks on leaves
  • Distorted or curled leaves
  • Reduced growth or stunted plants
  • Wilting or yellowing of leaves
  • Black, sticky residue (honeydew) on leaves and nearby surfaces
  • Tiny, dark, moving specks on leaves and flowers
  • White, cloudy, cobweb-like material on leaf undersides
  • Flower petals with brown or black discoloration
  • Stunted or distorted flower growth

Note: These symptoms may also be caused by other environmental factors or pests, so it’s important to accurately identify the source of the issue before taking action.

What is a Thrip

  • Small (1-2mm in length)
  • Slender and elongated body with a narrow waist
  • Dark brown or black in color
  • Two pairs of wings, held roof-like over the body
  • May have stripes or patterns on the wings or body
  • Translucent or partially translucent wings
  • Triangular head with large compound eyes
  • Mouthparts located at the front of the head and designed for piercing and sucking sap from plants.

Treating a Thrip Infestation

It may be necessary to use multiple methods to effectively control thrip infestations in a garden. For example, cultural controls such as promoting healthy plant growth and removing infested plant parts can help reduce stress on plants and prevent infestations. Meanwhile, physical controls such as using row covers and high-pressure water spray can help prevent thrips from reaching and feeding on plants.

Cultural Control

  • Maintain healthy garden conditions: Provide adequate moisture, light, and nutrients to plants to promote growth and reduce stress, which can make them more resistant to thrips.
  • Remove infested plant parts: Regularly remove and dispose of infested plant parts to reduce thrip populations.
  • Avoid overcrowding: Space plants properly to promote good air circulation, which can help prevent thrips from establishing themselves in large numbers.
  • Use sticky yellow cards: Hang sticky yellow cards in the garden to monitor thrip populations and help detect infestations early.

Physical Control

  • Use row covers: Cover plants with row covers to exclude thrips and prevent them from feeding on the plants.
  • Use high-pressure water spray: Spray high-pressure water onto plants to knock thrips off their foliage and disrupt their populations.
  • Use vacuuming: Vacuum thrips from plants using a handheld vacuum or shop-vac.
  • Use sticky bands: Place sticky bands around the trunks of trees and shrubs to trap and remove thrips before they can reach the foliage.

Biological Control

  • Encourage natural predators: Promote populations of beneficial insects such as lacewings, ladybugs, and predatory mites that feed on thrips.
  • Use predatory insects: Release commercially available predatory insects such as pirate bugs, minute pirate bugs, and predatory thrips to feed on thrip populations.
  • Use nematodes: Apply beneficial nematodes to the soil to control thrip larvae.

Chemical Control

  • Use insecticidal soaps: Apply insecticidal soaps to the foliage of infested plants to kill adult thrips.
  • Use horticultural oils: Apply horticultural oils to the foliage of infested plants to smother thrips and their eggs.
  • Use insecticides: Apply insecticides such as neonicotinoids, pyrethroids, and carbamates to the foliage of infested plants to control adult thrips.
  • Rotate insecticides: Alternate between different types of insecticides to reduce the risk of thrip populations becoming resistant to a single product.