How to get rid of Thrips

thrips thysanoptera how to get rid of

Thrips are also commonly known as storm flies, storm bugs, thunderflies, thunderbugs, corn flies, and corn lice, and are small insects that belong to the order Thysanoptera. They feed on a variety of small animals and plants, which they puncture and whose insides they consume. Some species of thrips feed on insects that are labelled as pests, and so they are considered to be beneficial, while others feed on plants that have commercial value (i.e. vegetables such as onions, beans, carrots, squash, etc., and flowers such as gladioli, roses, etc.), and are thus considered to be pests.

thrips thysanoptera how to get rid of

What’s more, thrips can also be carriers of plant diseases, such as the Tospovirus, the Tomato Spotted Wilt Virus and the Impatiens Necrotic Spot Virus, easily spreading infections from plants to plants. Some species of thrips (e.g. Franklinielle tritici, Limothrips cerealium, etc.) may even bite humans; although these species do not feed on blood and do not transmit any diseases, they can still cause irritation.
With the right conditions, such as those in a greenhouse, both categories of thrips, those that are considered to be beneficial and those that are pests, can increase in population exponentially, forming large swarms that are more than a nuisance to people.

Signs of infestation

Detecting a thrips infestation in its early stages is key to subsequently tackling the problem successfully. Do not rely on simply sighting them, seeing as some species of thrips are not considered pests, feeding on things such as pollen, and thus do not require removal. Instead, it is extremely important to regularly inspect your plants; keep an eye out to observe damage (such as discoloration and deformities), as well as clusters of thrips in places where leaves are attached to stems. Pay especially close attention to the second suggestion; before deciding on a course of action, it is very important not only that you have identified the infestation, but that you have identified it correctly. Keep in mind that there are a couple of pests that cause similar damage to that of thrips (e.g. mites, lace bugs, etc.).
If you suspect thrips have come into your growing area, gently shake foliage/flowers over a piece of white paper to knock some of them off for closer inspection. You can also use sticky traps to monitor the thrips population, as it will help you see the level of infestation.

As they are almost impossible to maintain at bay completely, you must ensure that the population is strictly controlled by:

  • reducing the places where thrips may breed;
  • removing weeds and unnecessary grass;
  • removing plant debris while it is still green;
  • inspecting all the plants you buy before you bring and plant them into your garden;
  • removing spent blossoms;
  • providing good, constant irrigation to plants;
  • applying mulch;
  • using row covers, hot caps, or other kinds of cages with a fine mesh in order to keep thrips (and other insects) away from vulnerable vegetables or young plants; once the latter become larger, though, it is important to remove the covers, allowing them enough growing space;
  • if you have found an infested plant, you can prune and remove any areas that are injured; if the infestation is severe, though, we recommend that you get rid of the entire plant; place it in a trash bag, tie it securely, and only then place it in the bin.

Natural control methods

You can start tackling a particularly heavy infestation with ‘preliminary’ measures, such as knocking down the thrips with a pressurised water hose and setting sticky traps in strategic places.

Using natural predators is another option when it comes to taking preventive or controlling measures against these pests. In terms of biological control, it must be said that there are few predators that are effective against thrips. This is due to the small size and the high rates of reproduction that they have, which implies that predators not only have to be small and slender themselves, in order to penetrate all the cracks and crevices where thrips may hide, but they also have to pray extensively on eggs and larvae. However, there are options to choose from: the two families of parasitoid Hymenoptera (insects), the Eulophidae and the Trichogrammatidae, as well as aphid wasps, minute pirate bugs, mites, ladybugs, green lacewings, and even species of predatory thrips. What can be used more effectively are biological insecticides, such as Beauveria bassiana and Verticillium lecanii, both fungi that act as parasites to a number of species of insects, including thrips.

Another way of naturally fighting thrips is by using insecticidal soap, which is a neem based solution, that can be diluted and sprayed on infected plants, or poured around them. Neem oil can also help in getting rid of them at all stages of development, as it does not pose a threat to beneficial insects either.
Spinosad products are organic and unlike many other thrip pesticides, completely harmless to pets, children, and plants. They are based on chemical compounds found in the bacterial species Saccharopolyspora spinose, and can be used directly to kill thrips on contact, but can also be used when watering plants to systematically kill thrips via the roots. As it is an organic insecticide, spinosad effective for only about 24 hours after being mixed with water, so only mix as much as you will need per application.

Traps for Thrips control:

Traps are used to monitor or reduce the population of insects or other pests. They can be used against crawling, flying insects, mice, rats, cats, dogs, snakes or other pests. Glue traps are ideal for catching cockroaches, as they can also help in monitoring their population.

You can use sticky traps when it comes to attracting and catching the thrips. They are most attracted by blue coloured traps, which you can use by hanging them around the infected plants. You can gentle shake the foliage to dislodge the thrips, causing them to take flight and get stuck on the adhesive. This method uses no pesticides, poses very little threat to other wildlife, and is relatively weatherproof. It will require changing out the tape after it’s captured a lot of thrips, though.

Chemical control methods

The problem with aggressive chemical solutions when it comes to thrips is that they are very likely to also kill the insects that are beneficial. Systemic neonicotinoid insecticides, for example, can provide relatively rapid control, and can have low, moderate, or severe impacts on the surrounding environment, depending on the brand of the product, on the situation at hand, as well as the species and the life stage of beneficial insects that are unlucky enough to come in contact with it.
The same can be said about pyrethrin-based sprays, with the only advantage of these being the fact that they stop being toxic very quickly following application; beneficial bugs that may find their way into your garden after a couple of days, therefore, will not be harmed.

Thrips are also problematic because, as mentioned above, they are small, they move very quickly, and they also breed very quickly, with eggs and larvae largely protected against chemical actions. Therefore, a good chemical treatment depends on a number of different factors, such as timing of application, treatment of the right plants, adequate spray coverage of these plants, etc. Before you commit to a certain insecticide, we recommend that you do a bit of research on the species of thrips that the infestation is composed of and on the type of plants that are affected by it; once you have done this, you can pinpoint the right insecticide to use. Be sure to read the labels and the instructions in full to avoid encountering any type of problems.
Overall, we recommend that you do not immediately jump to an aggressive chemical solution unless the circumstances warrant it; the damage that the thrips have already caused to your plants will not go away, so the best that you can do is ensure that they are protected from then on, not damage them even more through the use of aggressive chemicals or, indirectly, through the disappearance of beneficial insects.

That being said, the chemical solutions that are most effective during a thrips infestation are contact insecticides, which do not leave permanent residues and do not harm other species of beneficial insects. These include: azadirachtin, insecticidal soaps (which you can find in commerce or make yourself, by mixing certain household soaps), and neem oil. These must be applied to completely cover every area of a plant where thrips are present. Unless the label gives you different instructions, repeat the application periodically, until all the pests have been killed.
You should use control strategies that include the least toxic insecticides along with making sure you use good cultural practices, such as providing consistent watering and cleaning up dead or diseased plant material. As we have seen, thrips are difficult to control successfully, without creating more damage elsewhere. The best strategy involves a mix of good gardening practices, natural enemies, and the least-toxic insecticides that are effective. It is very important to constantly apply preventive measures as well, and for more details regarding those, you can visit our article about ways in which to ‘Prevent infestation with Thrips’.

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