Thrips are very common garden pests for most indoor and outdoor plants and can be very difficult to eradicate once they’ve taken hold in your garden.
They commonly affect a wide variety of herbaceous ornamentals and woody plants, including azalea, dogwood, gardenia, and hibiscus. Thrips are also known to eat up fruit trees and vegetables, such as citrus, olives, onion, squash, pepper, carrots, strawberries, and grapes.
If you find that you have a thrips infestation, there are several ways to tackle it:
- Prune heavily infested limbs and dispose of them properly.
- Blast the thrips off infested plants with a strong stream of water.
- Treat infested plants with a Neem oil solution.
- If the Neem solution doesn’t work, treat infested plants with a Pyrethrin solution.
Note that a Neem oil solution can be used weekly in a preventative manner. It is better to use Neem oil than pyrethrin solutions because Neem solutions are less harmful to beneficial insects.
“Thrips” is the singular and plural term applied to very small, slim insects you may find in your outdoor garden or among your wide range of houseplants. You may also hear them referred to as “Thunderflies.”
Female thrips, which are bigger than males, usually lay eggs in the host plant. They can produce and deposit eggs without a mate in the plant tissues, making adult females harder to control.
Because thrips are so very small, you may be unaware of their presence until their numbers have become very great and they have done a lot of major damage.
These nearly microscopic bugs may be either friends or foes. Some plant predators use their rasping mouthparts to hack through leaves, buds, and flowers in search of sap.
Some slightly larger thrips are beneficial thrips that feed on the smaller thrips and many other minuscule insect pests.
In fact, there are approximately 5000 different kinds of thrips. Of these, only a couple of hundred thrips species are pests. The remainder is beneficial.
Thrips Can Be Damaging To Your Plants At All Life Stages
When pest thrips attach to your plants, both the adult and nymph varieties can cause great harm by physically injuring the plants and sucking out the plant juices.
When this happens, the undersides of leaf may have a speckled, silvery appearance with black spots. Buds and flower petals will become discolored and distorted. Thrips predation may also spread bacterial and viral plant diseases.
In addition to causing direct damage to plants, adult thrips also make a mess and potentially starve plants of sunlight by producing great quantities of hard, brittle excrement.
This substance collects over the plant’s leaves, stems, buds, and blooms in an unsightly and unhealthy manner and may cause sooty mold to develop. Moreover, they are also known to spread fungal spores and plant viruses.
Inspect Carefully For Thrips
It’s a good idea to check your plants frequently for thrip infestation. To recognize these common pests, get out your magnifying glass and have a look.
They are slender insects, about the size of a grain of wild rice, very long and thin (1/20th of an inch long), and may be rust-colored, black, or white.
Most species of thrips are winged, but they do not fly well. Instead, they use their wings hang-glider-like to help them blow about purposefully in the wind. In addition, certain varieties of thrips have vestigial or fringed wings that make them poor fliers.
Test To See If Your Plants Have Thrips
To check your plants for adult thrips, go into your garden with a sheet of white paper and a magnifying glass. Hold the white paper under the host plant you suspect is infested and shake its limbs.
If there is the presence of thrips on the plant, they will fall onto the paper. Then you can examine them under the magnifying glass and identify them.
It’s well worth noting that this is a good way to reveal and identify many different kinds of tiny plant pests. Even if your problem isn’t thrips, shaking the pests onto paper and scrutinizing them closely is an excellent step toward identifying and dealing with your insect enemy.
Another way of isolating and identifying thrips is to occasionally set up sticky yellow traps to find out what insects are in your garden. It’s not a good idea to use sticky traps on an ongoing basis because they catch beneficial insects and pests.
Furthermore, they are not really effective in controlling pest insects. They are just a good, occasional identifying tool.
Watch For Symptoms Of Thrips
Because they are so small and tend to hang out on the underside of leaves, you may not know you have a thrips problem until it becomes a big problem. Thrip damage to your indoor plants is easy to identify.
Watch for:
- Falling or deformed leaves
- Bleached or yellow leaf spotting
- Stunt plant growth
- Deformed or stunted blooms
- Varnish-like excrement coating the plant
Other tell-tale signs of thrips are the distorted leaves and “thrips poop” or the dark deposits they leave behind. The black spots are usually combined with wrinkled infected leaves.
If the damage you find is mostly isolated to new leaves, thrips are the most likely culprit. You may have aphids if the damage is more concentrated on infested leaves and stems. It’s possible to have both. Aphids are also tiny, active, green, white, or cream-colored, and have soft, oval bodies.
How To Get Rid Of Thrips In Your Garden
1. Prune and dispose of it correctly.
Use a very sharp, sterilized pruning implement to prune away all damaged, infested foliage, stems, and branches. Burn the infested foliage, limbs, and stems of the infected plants immediately.
Avoid allowing the pruned vegetation to lie on the ground in your garden. Put it into a bin to transport it to the fire.
If you cannot do this, put the branches right into black plastic bags to be sealed and set out with the trash. The heat from the sun will kill the thrips in the bags.
Note that you may be better off completely disposing of heavily infested plants, roots, and all, rather than trying to save them through pruning.
2. Drown remaining thrips.
After you’ve pruned, blast your garden plants with strong blasts of water from your garden hose. Be sure to get leaf tops and bottoms.
If you are treating indoor plants, you can rinse them in the sink or shower. Follow up with thorough spraying with a solution of one gallon of water mixed with a couple of teaspoonfuls of dishwashing liquid soap (not detergent) or horticultural soap.
This mild solution will kill off any remaining thrips but will not keep them away. You can treat weekly with a Neem oil solution (step 3) to prevent thrips’ return.
For outdoor plants, use insecticidal soap and thoroughly apply it to all parts of the plant. Using this solution will kill thrips while keeping the environment friendly.
3. Neem oil is a good treatment and deterrent.
You can purchase a commercial Neem spray solution or make your own by adding four teaspoonfuls of Neem oil concentrate to a gallon of water and the dish soap recipe mentioned in step 2.
This all-natural treatment contains (Azadirachtin) which is a natural pesticide and one of the recommended organic pesticides. It disrupts the pests’ life cycle and interferes with their desire to mate and eat.
After you’ve pruned and water-blasted thrips in your garden, follow up with a Neem oil spray to kill any stragglers. It will not kill them instantly but prevent them from thriving and reproducing.
However, neem oil has some residual effect, so a weekly treatment will help keep thrips, aphids, and many other pests off your plants without harming beneficial insects that do not eat plant matter and drink plant sap.
Neem oil can harm honeybees and other pollinators if they encounter it right after spraying it. For this reason, it’s best to apply Neem products at dusk so that pollinators do not come in direct contact with them in liquid form.
Related: Learn about Western Flower Thrips Damage and Control
4. If all else fails, use Pyrethrin.
Although Pyrethrin is a fairly natural pesticide made using chrysanthemum flowers, it can harm beneficial insects. It’s another effective way to disrupt the thrip life cycle.
If you’ve faithfully applied all of the thrip control methods above for a couple of weeks but still see thrips and their damage, you may need to treat them with a Pyrethrin spray.
Typically, you should provide two applications four days apart. Be sure to follow the packaging directions carefully.
Once your thrips problem is under control, you can go back to using vigilance and Neem oil solution as preventative measures.
What about pyrethroids?
Pyrethroids are synthetic chemical pesticides. They can damage beneficial insects and soil-dwelling fauna, such as earthworms. Additionally, thrips can easily become resistant to pyrethroids with repeated applications.
You are far better off using a combination of natural coping and preventative methods and encouraging a healthy population of natural predator insects in your garden.
Prevention Is The Best Cure
It’s a lot easier to prevent a heavy infestation than to battle one. The steps needed to keep thrips out of your garden really boil down to good stewardship.
Follow these steps to discourage thrips and quite a few other garden insect pests:
- Keep your garden clean and tidy, especially around vulnerable plants. Prune away dead and damaged vegetation regularly and dispose of it promptly. Dead leaves and branches, plant debris, crop debris, leaf litter, spent flowers, and damaged vegetation provides hiding places, egg-laying territory, and overwintering possibilities for garden pests.
- Encourage beneficial insects to control the thrip population. Predatory mites, lacewings, and minute pirate bugs are well-known predatory insects of thrips. In addition, learn to identify the bugs in your garden and do not harm the natural enemies of thrips, such as predatory cucumeris mites, Trichogramma wasps, minute pirate bugs, lacewings, ladybugs, and more.
- Plant aromatic herbs among your garden plants. Herbs such as basil, oregano, rosemary, catnip, and the like are repellent to thrips. Members of the Allium family (e.g. onions and garlic) also repel thrips.
Thrips are just a fact of life for most gardeners. They multiply rapidly and move from plant to plant by crawling, flying, and being blown in by the wind.
A combination of vigilance and prevention is the best way to prevent thrips damage to your herbaceous plants and garden.