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Thrips

Garden pest · Thysanoptera

Description​

Thrips are tiny, slender insects in the order Thysanoptera. Many species feed on garden plants, including vegetables, fruit, and ornamentals, although some thrips are predators of other small insects. Plant-feeding thrips scrape cells and suck out their contents, leaving pale speckles that can merge into silvery or bronzed patches. Feeding on buds and young growth can distort leaves and flowers; feeding on developing fruit may leave rough, corky scars. Some species also spread plant viruses, notably tomato spotted wilt virus. Thrips often hide deep in flowers, folded leaves, and growing tips, so damage may be more obvious than the insects themselves. Their populations can rise quickly in warm, dry conditions. Adults can fly or be carried on wind or new plants, while immature stages remain close to feeding sites. The severity of damage depends on the thrips species, the plant, and how early feeding begins.

Symptoms​

  • Pale speckles or stippling
  • Spots on leaves
  • Curled or cupped leaves
  • Distorted new growth
  • Stunted growth
  • Flowers or buds dropping
  • Insects visible on the plant

How to Identify​

Look closely at flowers, leaf undersides, and tender shoots for narrow, fast-moving insects, usually about 1–2 mm long. Adults have slender, fringed wings; young thrips are wingless. Tap a flower or shoot over white paper to make them easier to see. Silvery feeding scars, distorted petals or leaves, and tiny black fecal specks are useful clues. Spider mites can cause similar pale speckling but may leave fine webbing; aphids are broader-bodied and often produce sticky honeydew. Sunscald and nutrient problems do not leave insects or black fecal specks. Identify the species if possible, since some thrips found on plants are beneficial predators.

Prevention​

Inspect new plants, especially flowers and growing tips, before bringing them into the garden or greenhouse. Remove weeds and old crop debris that can shelter thrips, and avoid keeping heavily infested plants beside healthy ones. Maintain even watering to reduce plant stress, but do not rely on watering alone to prevent infestation. Monitor susceptible plants regularly: tapping flowers over white paper can reveal thrips before damage becomes extensive, while sticky traps can help track flying adults. Encourage natural enemies by growing a variety of flowering plants and avoiding broad-spectrum insecticides. In a greenhouse, insect screens and prompt removal of infested material can help limit spread. Where thrips-borne viruses are a concern, remove infected plants promptly; controlling thrips after infection will not cure the plant.

Treatment​

Start by checking how widespread the infestation is. Remove badly damaged flowers or shoots, and dispose of them away from the garden; existing scars will not heal. A firm spray of water can dislodge thrips from sturdy plants, especially leaf undersides. Recheck often because insects hidden in buds may escape. In greenhouses, suitable predatory mites or minute pirate bugs can suppress thrips when introduced early; use a supplier’s guidance for the crop and conditions. If needed, apply insecticidal soap or horticultural oil thoroughly to feeding sites, testing a small area first and following the label. These products work mainly on insects they contact, so repeat applications may be necessary. For persistent infestations, a labeled spinosad product is an option, but it can harm bees while wet: never spray open flowers or when pollinators are active. Avoid routine broad-spectrum spraying, which can kill predators and encourage resistant thrips.

Plants Affected​

Anthurium, Basmati Rice, Carnation, Chives, Daylily, Freesia, Garlic, Gladiolus, Indica Rice, Kalijira Rice, Leek, Lisianthus, Onion, Petunia, Shallot

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