Thrips is a common pest on houseplants. The insects are so small that they are difficult to see with the naked eye. Do you notice your plant turning yellow or even spotty reddish-brown? If so, you could be suffering from a thrips infestation! Use a magnifying glass to check the leaves, including their undersides, and the stems. If the thrips plague is already in an advanced stage, you may also see white flies. With this pest it is important to act quickly! Fortunately, you do not have to be alarmed, you can easily fight these pests. Before you start it is good to know something about the life cycle and distribution of thrips.
What are thrips?
Thrips, also known as thunderflies, are small insects that feed by sucking sap from leaves. They are long, slender insects about 1 to 2 millimeters in length. Yellow, black or brown are the most common colors for adults, but the larvae are usually yellow or green. The insects fall into the Thysanoptera order of insects. This difficult name is a Greek compound of Thysasos (frayed) and Pteron. The latter means wing and makes it immediately clear why a thrips pest is so dreaded
There are over 4500 species and although there are many varieties that can cause great damage to a plant, there are also species that are very useful. These useful species will attack other insects, including other thrips. Unfortunately, it is difficult to tell the good ones from the bad ones, so most choose to control thrips anyway.
The life cycle of a thrips consists of five distinct phases. From egg to larva, pre-pupa, pupa to adult. Female thripses live about 30 days and lay about 2 to 10 eggs per day. The eggs are inserted into soft plant tissues such as the leaves, stems or flowers. The larval stage consists of two stages that feed and develop on the leaves. The pre-pupa and pupa stages usually complete their development on the potting soil, but pupation can also occur on the leaves of the plant. The pupa is the stage where the wings are formed. Depending on the temperature in the room, an egg develops into an adult in up to 19 days. Normally, male larvae are born from unfertilized eggs in most insects, while a fertilized egg becomes a female. Many thrips species can reproduce even when there are no males around. In this case, an unfertilized egg also produces a female larva. These are actually almost clones of the mother thrips.
An adult thrips has wings, but cannot fly very well. They make short flights from leaf to leaf or between plants. Still, they can spread quickly by taking advantage of wind currents. A draught or someone walking by causes wind currents which they can use to hitch a ride. They can also be spread at all stages by clothing, pets, plant tools or by another plant.
How do I recognise thrips?
If you suspect you have a thrips infestation it is recommended to take a magnifying glass with you, because these insects are extremely small! Thrips are almost impossible to see with the naked eye. Without a magnifying glass, they look like little black stripes or dots. An adult thrips is brown to black in color and has a length of 1 to 2 mm. Baby thrips or thrips larvae are about 1 millimeter in size and yellow or green in color. Their slender bodies are reminiscent of an inimini grain of rice.
And yes, it is one thrips, two thrips. The singular and plural of the name are the same! And it might as well always be plural, because where there is one, there are usually many more unfortunately....
Thrips have sucking mouthparts that pierce the surface of leaves and stems, slurping in plant juices. This feeding results in stippling, discoloration and scarring on stems, leaves, flowers and buds. Tissue deformation and even growth retardation can also occur. The damage done by thrips can be confused with that of other sucking insects and mites that cause stippling.
Laying eggs results in scarring and yellow spots. This is because they lay their eggs in the soft plant tissues. When they inject enzymes, silver or bronze speckles may appear. As if that wasn't enough, they also leave behind pathogens and small grains of black insect poop! Not a pretty sight and certainly not pleasant for your plant. Besides this external damage, the chances of fatal damage are super slim. The biggest threat to your plant are thrips that carry viruses and infect your plant with the virus while feeding.
How do thrips damage my plants?
Thrips, as well as their eggs or larvae, are often brought in through new plants, clothing or pets. They are not good fliers, but with their short flight they can spread quite a bit!
Thrips have sucking mouthparts with which they cause the greatest damage to plants and flowers. First they rasp open the cells and actually cause a kind of wound on the leaf or stem. The wound exudes plant sap where the thrips insert their snout and absorb plant juices from the damaged cells. The leaves are eventually so affected by this that they turn yellow or brown and will eventually fall out. Your plant will slowly deteriorate and may eventually die if you don't start fighting the infestation in time.
Unfortunately, that's not the only way thrips causes damage to your plant. If you've hit it really bad, thrips may make your plant even sicker. Thrips are known to transmit plant diseases and viruses to the plant when they get their snouts into the plant. The two best known are Impatiens Necrotic Spot Virus (INSV) and Tomato Spotted Wilt Virus (TSWV). Both can seriously damage or even kill certain plants. Super important to keep infestations of these mini insects well under control!
Impatiens Necrotic Spot Virus (INSV)
The symptoms of this virus vary. Sometimes they are described as similar to brown chicken pox or ringed spots. By the way, if you see this it doesn't necessarily mean your plant is suffering from the virus, but the symptoms do indicate a problem!
Tomato Spotted Wilt Virus (TSWV)
This virus is especially harmful to fruit plants or trees. The symptoms of TSWV are primarily bronzed leaf surfaces, dead or brown spots, and sometimes deformed leaves that curl downward.
How can I prevent thrips?
Prevention is better than cure, but unfortunately you can't prevent thrips 100%. However, you can take a few precautions to reduce the chances of a nasty thrips infestation.
Water & humidity
Plants with a dry soil have a greater chance of being attacked by thrips. They don't like moisture very much! So keep your plants a bit moist and increase the humidity in your home with for example a humidifier. Always pay attention to the water requirements of your plant. One plant prefers a moist soil than the other...
A well cared for and healthy plant is the best protection against diseases and plagues. Make sure that your plant is in the right location, gets the right amount of light and water and give it some extra plant food once in a while. If it should happen that a thrips plague occurs, the plant is strong enough to survive this attack. Cuttings and young plants often do not have enough strength to withstand an attack on their delicate roots. If you suspect that you have an infestation of thrips, keep a close eye on it and intervene as soon as possible!
How can I control thrips?
It can be quite difficult to control a thrips infection, but luckily we have some tips that can help you get these pesky critters under control. Thrips like low humidity, so it helps to increase the humidity and water your plants regularly. You can also control thrips with biological control agents or natural enemies!
Fight thrips with neem oil
Neem oil is a natural essential oil that works wonders in treating and preventing pests! Because of its smell, it has lasting effects on the plant. This wonder drug is included in the PLNTSdoctor Kit. To ensure that the goodness "sticks" to the leaves of your plant, you mix the neem oil with water and natural detergent. Pour the mixture into a plant sprayer and apply it to the underside of the leaves. Reapply every few days until the thrips are completely gone. Also, be sure to remove any dead insects after the oil has done its job. Neem oil can also be used very well preventatively to protect your plant from pesky insects, pests and fungi. Just make sure you don't place the plant in direct sunlight afterwards. The oil can retain a little heat and can thus burn the leaves of the plant!
Ecokuur Leaf Insect Spray
This insect spray is an alternative to chemical pesticides. It is safe for humans, animals and the environment and therefore perfect for a simple way to combat your affected plant. Spray the product homogeneously over the plants where you have spotted the thrips. Do not forget to include the underside of the leaves, this is where the thrips usually are! Treat from the moment you see the first insects and spray twice a week, with one week in between.
Fight thrips with predatory bugs (biological pest control)
It is possible for you to fight off trips in a natural way, with biological pest control. These bugs are called ‘Amblyseius swirskii’ and are about 0.5 mm in size. So very difficult to see with the naked eye. They can eat 4 thrips larvae a day and protect your plant with this for approximately 6 weeks. If there is nothing left to eat, they die. Don't feel guilty, this exact process happens in nature.
This was a short explanation of our pest control against thrips, if you would like to know more you can read our blog: ‘Which natural and biological pest control against which pest?’.
PLNTS hacks against thrips
If you go online and look for the best way to combat thrips you will come across many options. It is good to know that there is not one specific method that works for everyone. For some plants one way works better than another. It's just a matter of trying it out!
Below you will find a number of alternative hacks that will help you recognize and combat thrips.
Mourning Fly Catchers
A solution to not give thrips a chance in their adult phase are our 'Mourning Fly Catcher'! These sticky insect strips ensure that the flying insects are attracted by the bright color and then stick to it! Cut the strips into several small strips so you can put them in multiple plant pots.
Fighting thrips with methylated spirits
Another remedy that is often used as a pesticide against pests is methylated spirit. Mix about 20 milliliters and 20 milliliters of biodegradable detergent with a liter of water. Spray the plant regularly with the soap mixture and the thrips will eventually disappear completely.