Thrips

Thrips are very small, elongated, piercing-sucking insects, 1 to 2 mm (about 0.04 to 0.08 in) long. They pierce surface cells on leaves, flowers, or stems to suck out their contents, leaving characteristic silvery patches. The thrips treatment explains how to break their life cycle.

An uncontrolled infestation distorts new shoots, weakens the plant, and can transmit viruses.

Signs to check

• Silvery streaks or spots on leaf surfaces that do not come off when cleaned.
• Numerous tiny black dots (droppings) on affected areas, often on the undersides of leaves.
• Mobile, elongated yellow, brown, or black insects, 1–2 mm (about 0.04–0.08 in) long, visible to the naked eye when inspecting the plant.
• Distortion, discoloration, or stunting of new leaves and flower buds.

What you may see

• Distorted or bumpy fruit · Fruit has an irregular shape, with bumps, hollows, or visibly asymmetric growth on its surface.
• Distorted or twisted leaves · Leaves grow abnormally, appearing curled, swollen, twisted, or unusually small on the plant.
• Black dots (droppings) · Tiny, dry black dots, often round and slightly raised, are scattered over leaf surfaces.
• Yellow stippling and fine webs · Tiny yellow or white dots scatter across leaves, giving them a stippled appearance, often accompanied by fine spider-like webs.
• Silvery patches and streaks · Shiny, silvery marks or patches appear on leaf surfaces, making them look discolored in places.

What to do now

Thrips treatment

1. Isolate the infested plant immediately to prevent spread to others. Adult thrips can fly short distances.
2. Shower the plant thoroughly. Use a stream of lukewarm water to physically dislodge as many adults and larvae as possible from both sides of leaves.
3. Spray a black soap solution. Mix 15 to 30 mL (about 1 to 2 measuring tablespoons) of liquid black soap into 1 liter (about 1.06 US qt) of lukewarm water. Apply generously over the whole plant, including the undersides of leaves.
4. Install blue sticky traps. This color is particularly attractive to adult thrips and helps reduce the flying population while monitoring the infestation.
5. Repeat the black soap treatment every 3 to 5 days for at least 3 weeks. This frequency kills newly hatched larvae and breaks the life cycle.

Rinsing foliage

1. Place the plant in your shower or bathtub. If it is too large, tilt it outdoors.
2. Wrap the base of the pot in a plastic bag to avoid completely soaking the potting mix.
3. Set the water to moderate pressure and a lukewarm temperature. Water that is too forceful or too cold could damage the foliage.
4. Rinse each leaf thoroughly, focusing especially on the underside, where pests like to hide.
5. Do not forget stems and leaf axils, where leaves join the stem.
6. Let the plant drain completely for at least 20–30 minutes before putting it back.
7. Ensure good air circulation around the plant so leaves dry quickly, helping prevent fungal diseases.

Prevention

• Quarantine every new plant for 2 to 3 weeks before placing it near the others.
• Carefully inspect the undersides of leaves every week when watering.
• Maintain high ambient humidity by misting your plants or using a humidifier, because thrips dislike humidity.
• Clean leaves regularly with a damp cloth to remove dust and any pests.
• Inspect the undersides of leaves once a week for early signs.
• Shower plants that tolerate it once a month to remove dust and any pests.
• Maintain high ambient humidity above 50% to discourage spider mites, which thrive in dry air.