What are thrips?
Thrips (Thysanoptera), also known as fringed-wing insects, are pests that primarily infest houseplants. As they feed on plant sap, they can cause significant damage to plants.
How to identify thrips
Thrips look like small dark streaks on the leaves. The tiny insects, up to three millimeters in size, are usually yellow to dark brown and very slender. Adult thrips have striped, narrow wings on their backs, which is why they are also called fringed-wing insects. Their larvae look like small yellow, light green or whitish worms and are usually found in the soil or on the undersides of leaves.
Signs of thrips damage on plants
Since thrips are hardly visible to the naked eye due to their size, an infestation often only becomes apparent when the plant looks sickly. In particular, silvery, white spots on the upper side of the leaves and on the flowers indicate a thrips infestation. In addition to these feeding marks, tiny brown dots, which are the insects' excretions, as well as the light-colored larvae, can often be seen on the underside of the leaves upon closer inspection. Infested plants often show stunted growth and new leaves look deformed. By extracting the plant sap and nutrients, the affected plants are significantly weakened, which in the worst case can lead to the death of the plant.
- Feeding marks: silvery spots on the leaves
- Growth disorders: low to stunted growth or deformed leaves
- Weakened plant: overall sickly-looking plant
Fighting thrips: Home remedies or chemical?
There are various ways to combat thrips. Often, simple home remedies are sufficient, especially if the infestation is detected early. However, with a stronger infestation, it may be necessary to resort to chemical means. In principle, it is advisable to first try natural methods. Regardless of which method you use, there are some basic steps you should take beforehand to get rid of the thrips:
- Isolate the plant: Plants with a thrips infestation should be separated from others to prevent spreading. Thrips do not tolerate humid and cool conditions well. If the weather is appropriate, you can also temporarily place the plant on the balcony or terrace.
- Shower: Thoroughly rinse the infested plant with cold water to wash off some of the thrips. Cover the surface of the soil with cling film or a plastic bag to prevent the pests or larvae from being flushed into the substrate.
- Replace substrate: Since thrips larvae often live in the soil, it is advisable to renew the soil anyway to prevent spreading.
- Spray: There are various chemical or natural remedies against thrips that you can regularly spray on the plant to get rid of them.
Home remedies against thrips
Before resorting to chemical agents, it is advisable to first use proven home remedies against thrips. These are generally gentler on the plant, less harmful to the environment, and also pose no health risk to you. You can prepare various mixtures yourself and spray them directly on the affected plants.
- Neem oil: Mix one tablespoon of neem oil with water and thoroughly spray the thrips-infested plant, especially the underside of the leaves. Alternatively, you can dab the larvae directly with a few drops of neem oil.
- Olive oil and dish soap: Take one liter of lukewarm water, add two tablespoons of olive oil and a few drops of dish soap, and spray the plants twice weekly with the mixture.
- Soap: Alternatively, mix a solution of water and soft soap and thoroughly spray the plant.
Using beneficial insects against thrips
The use of beneficial insects is an environmentally friendly method for controlling thrips. Natural enemies such as predatory mites, nematodes, and lacewing larvae have proven particularly helpful against thrips infestations, as they specifically feed on the pests and their larvae.
Blue sticky traps against thrips
Blue sticky traps are an effective addition to reducing infestations, primarily in combination with other control methods. Thrips are attracted to the blue color, stick to the traps, and die.
Chemical control of thrips
If you can't get rid of the infestation, it may sometimes be necessary to control thrips chemically. In specialized stores, you can find specific insecticides that are effective against sucking pests. Be sure to follow the manufacturer's instructions when using them. Wear gloves if possible and avoid inhaling the product; a mask may be useful, especially indoors. You should also ensure the plant is well-ventilated during treatment. Chemical agents are often very effective against thrips, but should always be used only as a last resort.
Thrips on Monstera, Orchid, and Co.: These plants are particularly susceptible
Houseplants such as Monstera, Calathea, Fiddle-leaf fig (Ficus lyrata), and orchids are among the particularly susceptible species to thrips infestation. Other ornamental plants such as palms or poinsettias are also frequently affected. Regular checks of these plants are important to detect and combat an infestation early.
Preventing thrips infestation
Thrips can be spread by wind or introduced through potting soil. Although an infestation cannot be completely avoided, there are some tips to prevent one:
- Increase humidity: Since thrips thrive in dry heat, you can increase humidity by regularly spraying the plants with water.
-
Regular checks: Especially in summer and at the beginning of the heating season, plants should be regularly inspected for signs of infestation.
-
Apply neem oil preventively: The oil is known for its insecticidal effect and helps as a preventive measure to keep thrips away. You can therefore regularly spray your plants with a neem oil mixture.
