Thrips are tiny insects that feed on the leaves, flowers and young growth of many indoor and greenhouse plants. They can be difficult to spot because of their small size, but the damage they leave behind is often much easier to recognise.
Identifying a thrips infestation early gives you the best chance of protecting affected plants and preventing the insects from spreading throughout your collection or growing area.
WHAT DO THRIPS LOOK LIKE?
Adult thrips are small, slender insects with narrow bodies. Depending on the species and stage of development, they may appear yellow, pale brown, dark brown or almost black.
Most thrips are only around 1–2 mm long, making them difficult to examine without a magnifying glass. Adults have narrow wings edged with fine hairs, although these details are rarely visible to the naked eye.
Young thrips, known as larvae, are usually smaller and paler than the adults. They may appear cream, yellow or light green and can often be found feeding on the undersides of leaves or inside flowers.
WHAT DOES THRIPS DAMAGE LOOK LIKE?
Thrips feed by piercing plant tissue and removing the contents of individual cells. This creates distinctive areas of damaged tissue rather than large holes in the leaves.
Common signs of thrips damage include:
- Silvery or pale streaks across the leaves
- Bronzed or discoloured patches
- Small black specks of insect waste
- Distorted or curling young leaves
- Brown marks on flower petals
- Damaged buds that fail to open properly
- Stunted or misshapen new growth
Heavy feeding can cause leaves to become dry, scarred or distorted. Flowers may develop streaks or brown patches, while badly affected plants can lose vigour over time.
WHERE DO THRIPS HIDE?
Thrips tend to shelter in narrow, protected parts of a plant. This can make them difficult to find during a quick inspection.
Check the following areas carefully:
- The undersides of leaves
- Inside open flowers
- Between tightly folded young leaves
- Around flower buds
- Along leaf veins
- Where leaves join the stem
Some stages of the thrips lifecycle may also develop in the growing medium or among plant debris, so inspecting the foliage alone may not reveal the full extent of an infestation.
HOW TO CHECK A PLANT FOR THRIPS
Hold a sheet of white paper beneath the leaves or flowers and gently tap or shake the plant. Any dislodged thrips will be easier to see against the white surface.
Look for tiny, narrow insects moving quickly across the paper. A magnifying glass can help you distinguish thrips from soil particles and other small insects.
You should also inspect damaged foliage closely. Silvery feeding marks combined with small black specks are a strong indication of thrips activity.
HOW BLUE STICKY TRAPS CAN HELP
Blue sticky traps are especially useful for catching adult thrips. The blue surface attracts flying thrips, which become caught when they land on the adhesive.
Positioning traps close to plant height can help you catch adult insects and identify where activity is concentrated. This is particularly useful in greenhouses, conservatories, grow tents and larger indoor plant collections.
Sticky traps will not catch thrips eggs or every immature stage living on the plant. They should therefore be used alongside careful plant inspection and appropriate control measures.
THRIPS OR SPIDER MITES?
Thrips and spider mites can both cause pale or silvery damage, but there are some important differences.
Spider mites usually create fine webbing around leaves and stems. Their feeding often appears as many tiny pale dots across the leaf. Thrips are more likely to cause irregular silver streaks, scarring and small black specks.
If you can see fine webbing, spider mites are the more likely cause. If the plant has silvery scratches and narrow insects are found inside flowers or beneath leaves, thrips are more likely.
WHAT TO DO IF YOU FIND THRIPS
Move an affected indoor plant away from other plants where practical. Thrips can fly or move between neighbouring plants, allowing an infestation to spread.
Remove severely damaged leaves and spent flowers, provided this will not harm the plant. Check nearby plants carefully and position blue sticky traps around the affected area to catch flying adults.
Continue inspecting the plants regularly because newly developing thrips may appear after the first adults have been removed. Where additional treatment is required, always select a product suitable for the plant and follow its label instructions.
FREQUENTLY ASKED QUESTIONS
Can thrips fly?
Adult thrips have wings and can move between plants, although they are not usually strong long-distance flyers. Air movement can also help carry them through a greenhouse or indoor growing area.
Are thrips visible without a magnifying glass?
Adult thrips can be seen without magnification, but their small size makes them easy to miss. They may look like tiny dark or pale lines moving across a leaf or flower.
Do thrips live in houseplant soil?
Thrips mainly feed on foliage and flowers, but some species pass part of their lifecycle in the growing medium or plant debris.
What plants do thrips attack?
Thrips can affect a wide variety of ornamental plants, houseplants, vegetables, herbs and greenhouse crops. Flowering plants and tender new growth are particularly vulnerable.
Can sticky traps get rid of thrips?
Blue sticky traps catch adult thrips and can help reduce their numbers. However, they will not catch eggs or every immature thrips on the plant, so established infestations may require additional control measures.
