Flattened, silvery-white patches where the leaf has been hollowed out, scattered black specks of waste, and leaves that curl without dropping: this is thrips damage, caused by rice-grain-shaped insects of brown, grey or yellow. Catch it on the soft young tissue they attack first, and the infestation is still small and easy to treat.
Read on to discover what type of problems that result from thrips on plants. Included are images of thrips damage on fruit trees, flowers, and trees/shrubs. Damage can appear on leaves, stems, buds, fruits and flowers.
What parts of plants do thrips attack?
Usually, soft, young tissue is attacked first.
Also, buds, junctions and bends that are protected from wind, rain and predators are colonized early on.
Some species of thrips even attack roots underground.
Not all thrips are bad, however. There are some beneficial thrips that help eat up other pests and fungus!
The same feeding habit leaves a different mark depending on where the thrips are working. Use this to match what you are seeing on leaves, stems, flowers or fruits.
Thrips symptoms by plant part
Plant part
What the damage looks like
Colour
Other signs
Leaves
Flattened spots, lines and short trenches; the tissue below is hollowed out
Silver-white or yellow, later brown or rusty-red
Leaf loses its thickness and curls up; leaf drop is rare
Stems and leaf veins
Trench-like structures where the thrips feed
Brown rather than silver-white
Egg-nests show as light dots the size of a needle prick
Flowers
Wet-looking damaged spots or blotches on the petals, as if creased
Discoloured patches
Buds stunt and grow deformed when numbers are high
Fruits
Feeding marks on the outer skin only
Silvery-white, white-grey patterns
Cause of “silver banana”; the fruit is still safe to eat
Black dots that rub or shake off are the final confirmation: they are thrips waste, not fungal spore-sacs.
Damage to the whole plant
Leaves curl once the whole leaf is infected
With a magnifying glass, you can see the small insects crawling around.
Shake a leaf over a sheet of white paper.
Tiny specks will fall down on it.
If they’re a bit oval and long, shaped like a small grain of rice, they’re thrips!
They come in different colors, but usually brown, gray or yellow.
The main symptoms of a thrips infestation on a plant are the following:
leaves with spots that are silver-white or yellow, then turn to brown or rusty-red
leaf losing its thickness
as the entire leaf is infected, it curls up
leaf drop is rare
In some cases, thrips will trigger leaf galls (usually as part of the nesting/egg-laying process).
Damage to leaves
Flattened silver-white spots and lines on leaves
Skeletonised patches: cell contents gone, walls left
Telltale symptoms on leaves are that these spots often turn a silvery-white color. This may turn brown in time.
Thrips feeding spots turn white because the space below is hollowed-out. Contents like green chlorophyll are sucked out.
The skin and walls between groups of cells remain intact though. They form a kind of window that lets light through!
The botanical term is skeletonization – only the skeleton or structure of the plant leaf is left.
Typically, portions of leaves are flattened and aren’t as thick as the rest of the leaves.
Tissue collapses where the cells were drained
This is because thrips feed on the content of cells. Like mosquitoes, they drill beneath the surface or skin of the plant.
Thrips release enzymes that dissolve the inside of the plant into a nutrient-rich soup.
Afterwards, they suck the content up. This flattens the leaf in the area.
Patterns of damage are more like short burrows or trenches dug into the leaf and young stem.
They aren’t as long and twisted as leaf-miner damage, though.
As an individual or a colony advances, this can either resemble a line or a widening spot.
Black dots or tiny pellets are actually what’s left after thrips have digested everything. It’s their poo!
These black dots look a lot like the pycnidia spore-sacs on a plant that is suffering from leaf septoria.
Thrips egg-laying and larva damage
Lastly, depending on which species of thrips is attacking your plant, you may find damage due to “thrips nesting“.
As part of the thrips lifecycle, the female will lay eggs in a cut or on a leaf or stem.
These eggs hatch and the larvae secrete special chemicals to the plant around them.
Chemicals disrupt neighboring cells, making it easier for thrips to feed.
Sometimes damaged cells proliferate and form galls.
Symptoms of thrips on stems
On stems and on leaf veins, the damage has the same causes but may look a bit different.
Thrips feeding damage on stems
There are still trench-like structures where the thrips are feeding.
Usually the color is brown instead of silver-white.
Thrips nesting in stems
Egg-nests resemble dots that are white or light in color.
These spots are the size of the prick of a needle.
Learn more about thrips eggs and what they look like.
Symptoms of thrips on flowers and fruits
Young orange: skin marked, flesh still edible
Fruits contaminated by thrips
In citrus, banana, and other fruits, thrips will feed on the outer skin.
The skin will also turn silvery-white. This is the cause for “silver banana” disease.
Citrus fruits are also vulnerable to this. The skin is marked with white-gray patterns.
It’s still perfectly safe to eat the fruits, though.
Shown here is thrips on a young orange tree fruit.
Thrips on flowers
On aster, pollen feeders that sometimes attack petals
Usually, these thrips simply feed on the pollen and also help pollinate the plant. However, sometimes, they also attack flower petals.
Damaged wet spots or discolored blotches appear on petals, similar to when you crease or fold them.
Flower buds stunt and grow deformed if too many thrips are present.
How to tell Septoria damage and thrips damage apart
Mentioned above is Septoria, a fungus that infects many different types of plants.
Both have black spots, but those of Septoria are clustered together. They’re on the oldest spots. These spore-sacs don’t move when you rub your finger along.
Oppositely, black dots of thrips are their waste. They’re distributed more randomly, not only on the spots. They’ll fall off if rubbed or shaken.
Lastly, both Septoria and thrips result in flattened leaf portions.
However, edges around Septoria spots seem to swell and appear colored. This is because the plant is fighting the fungus back with an inflammation.
With thrips, portions of leaves that touch flattened spots seem very healthy. There is no swelling or change in color.
Another check you can do is verify whether your plant is prone to septoria infection or not.
About the same size as thrips is the red spider mite. However, its bright red color gives it away: not many thrips are as red!
Smart tip about thrips damage
As with most pests, take time every week to walk around the house or garden simply to admire your plants. Not only will this lift your mood, it will reveal thrips infestations while they’re still small and easy to treat!
Written by Gaspard Lorthiois | Loves helping out, especially when it comes to growing things. Worked in herbal medicine, runs a farm, and dabbles in tech. Master's degree and engineer.
My plant leaves have hundreds of tiny spots like they were sprayed with silver paint. The leaves are getting pale. My mungo pine leaves have folded up and are yellow.
Gaspard wrote on 7 April 2023 at 2 h 29 min
Hi Vicki, that might very well be thrips. Another possibility is spider mites.
Donna Walker wrote on 27 June 2022 at 7 h 59 min
What is wrong with my moonflower? It was doing beautifully. Had grown 5 feet tall and had 21 blooms one night. Suddenly, the leaves are skeletons. I would send u a pic.
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My plant leaves have hundreds of tiny spots like they were sprayed with silver paint. The leaves are getting pale. My mungo pine leaves have folded up and are yellow.
Hi Vicki, that might very well be thrips. Another possibility is spider mites.
What is wrong with my moonflower? It was doing beautifully. Had grown 5 feet tall and had 21 blooms one night. Suddenly, the leaves are skeletons. I would send u a pic.