natural and biological pest control
5 minute read

No time to read the blog? Then watch our PLNTSdoctor video! In it, Tessa explains all about how to tackle the most common pests in houseplants.

Which natural and biological pest control against which pest?

Yes, unfortunately, this too is an aspect of being a PLNTS parent. No matter how well you look after your green friends, there is almost no escaping it. For example, you take it inside on your clothes, it blows in through an open window or there is something in your new potting soil or on the new plant (that you have kept in quarantine for too short a time, it turns out afterwards). We are convinced that there is actually one really good way of controlling the various plant pests and that is biological pest control. This means that you introduce the natural enemy to your plants and they will then go to work to save your beloved plants. We understand that this is exciting and that you want to know all the ins and outs, especially before you actually release these little creatures on your plants. That's why we love to write this blog to help you become a real natural pest control expert. We will help you through it one pest at a time. Let's get started!

Troubled by Fungus gnats? The Steinernema feltiae (felti) to the rescue!

How do fungus gnats damage my plants?

Fungus gnats, or rather the eggs or larvae of the fungus gnats, are often brought in via your new plants or in new potting soil. Eggs or larvae may already be present in the soil and eventually spread to other plants. They can also simply fly in.

Female fungus gnats find potting soil the perfect place to lay their eggs. It is a moist environment, with lots of organic substances where the larvae can grow well. Unfortunately, these larvae are also the biggest problem. They end up doing the most damage to your plants. The youngest larvae mainly eat the algae and fungi in the potting soil, but the older larvae will also target the roots of the plant. When the roots of a plant are affected, the health and resistance of the plant also deteriorate. It will weaken, making it more vulnerable to diseases and fungi. This can eventually lead to a plant that is beyond saving. Of course, nobody wants that!

Fungus gnats

The Steinernema feltiae (felti) superpowers:

Felti are microscopically small nematodes that occur in the soil in nature and they are the natural enemy of the fungus gnat. As many as 1200 species live in the Dutch soil alone. These tiny fighters penetrate the larvae of the mourning flies and then excrete a bacterium that kills the larvae within 1-3 days. The great thing is that they do not affect the plants in any way. In optimal conditions, after 1-2 weeks there are fewer or no pests present in your plant(s). That sounds like music to your ears, doesn't it?

Steinernema feltiae

How to use?

It is actually very easy! Follow the following 5 steps and your plants will soon thank you:

  1. Add the bag of saviours to a watering can completely filled with lukewarm and clean water. This sachet is enough for one full watering can, which is about enough for 10 plants. There are five million saviours in one sachet, Wow!

  2. Stir for about 1 minute so that the nematodes are well distributed in the water.

  3. Pour the solution directly on your plants, all around the potting soil. Give as much water as you normally give to your plants.

  4. Keep the soil moist for another two weeks, so that the nematodes do not dry out. They also need water/moisture to move through the potting soil.

  5. We advise you to repeat the treatment. So order two sachets and use one sachet on day 1 (the day you received them) and use the second sachet on day 6.


Have you decided to order these saviours? Super! We do really recommend that you put the Felti into the plant immediately after receiving them. Do you want to keep these saviours for longer? Then keep them in the fridge between 4 °C and 8 °C. The nematodes can be kept for 1 week after receiving them, provided they are cooled. Do not keep the solution in water (in water? this will become clear later on).

Last but not least!

A single application does not guarantee that the mourning flies will disappear forever. In case of an infestation of a larger scale, we recommend you to apply these saviours several times. Wait 1 or 2 weeks each time to really see if your plant(s) are free of these gnats. It is also good to know that these saviours are not big fans of direct sunlight. So make sure that the plant(s) you release these saviours on is/are in a place where the sun never shines too brightly.

Troubled by Mealybugs? The Cryptolaemus montrouzieri (crypto) to the rescue!

How do mealybugs damage my plants?

Mealybugs, and their eggs or nymphs, unfortunately spread very quickly and easily. This can be caused by air currents, such as draughts, but also by cross-contamination. You can even carry the mealybug on your clothes (yuck!).

The nymphs and females bite on nutritious spots and suck the plant juices. This stunts the growth of your plant(s) and causes leaf malformation and yellowing. The result is reduced photosynthesis, so that the plant can no longer grow nicely. Most mealybug species bite their way through the leaf into the veins of the plant. Here they feed on nutrients. They can also find a way to the roots and feed on them! This gnawing causes leaves to turn yellow or brown and eventually die. Moreover, harmful viruses can be transmitted. So mealybugs harm your plants in many different ways - intense, isn't it?


The Cryptolaemus montrouzieri (crypto) superpowers:

Cryptolaemus montrouzieri, the natural predators of mealybugs, to the rescue! These very young (larvae) and hungry ladybirds will protect your plant against mealy bugs (and very occasionally scale insects as well) for about a month. We also call these saviours wolves in sheep's clothing. After all, they look rather like mealybugs. They have a white fluffy back and are therefore easy to see with the naked eye. In optimal conditions, these rescuers can eat up to 250 mealybugs. Yes, they are truly hungry! These fluffy bugs only stay on your plants so don't be afraid to find them all over your house. By using these rescuers you are making use of the natural way of pest control, and that is a good thing!

Cryptolaemus montrouzieri

How to use?

We can imagine that you first want to know how exactly to apply/use the Crypto. We can reassure you and tell you that we supply a super handy box with these saviours. You can easily empty the contents of the sachet, about 30 young ladybirds, into the box and then hang the box in your plant that is suffering from mealy bugs. These saviours like to walk upwards, so hang the box low in the plant, but of course close to the pest. You need at least one sachet per 1 m2 of planted surface area.


Can't wait to buy these saviours? Understandably so! However, we would like to point out that these crypto should be used immediately after receipt. If, for whatever reason, you would like to wait a little while before placing them. You can do this for 1 to 2 days in a dark, ventilated place at 12°C-15 °C. Not in the fridge! Also remember to grasp the bag with the Crypto carefully and do not squeeze the bag. This can damage these saviours and you don't want that to happen.

Last but not least!

A one-time application does not guarantee that mealybugs will disappear from the plants for good. In case of a large infestation we recommend introducing a bag of these saviours every other month. In addition, they are most effective when kept in a room between 20 and 28 °C and on a plant that is or will be slightly misted. However, make sure that the bag never hangs in bright sunlight.

Troubled by spider mites? The Phytoseiulus persimilis (persi) to the rescue!

How do spider mites damage my plants?

A spider mite infestation can be subtle at first. It may seem as if the plant is just taking a break. Sometimes you will see small cobwebs that the spider mites stretch on and between the leaves. It is only when you look really closely that you will recognise the spider mites. They are incredibly small! With the naked eye, spider mites look like red, yellow, black or brown (yes we know, lots of colours) moving dots.

A spider mite lives off the nutrients that flow through the veins of your plant. The juices flow through the veins and a spider mite, as it were, drills a hole with its snout, attaches itself and is completely filled with food without any effort! These tiny holes hinder the growth of your plant(s) and cause discolouration of the leaves, usually in clusters. The result is reduced photosynthesis, which stops the plant from growing nicely.

Spider mite.jpg

The Phytoseiulus persimilis (persi) superpowers:

These natural predatory mites are called Phytoseiulus persimilis and will overpower spider mite infestations in no time! They work invisibly and extremely fast, scouring your plants for spider mites. A predatory mite can eat up to 5 adult spider mites or 20 young spider mites (eggs) per day. What hungry little creatures, eh? When there are no spider mites left, these predatory mites eat each other and will eventually disappear from your plants. This is the way it is in nature. The predatory mites only stay on your plants, so don't be afraid of a house full of mites!

Phytoseiulus persimilis

How to use?

Naturally, you are curious about how to use these rescuers? We will gladly explain it to you! The Persi are delivered in sachets. This sachet comes with a very handy box. You can easily empty the contents of the sachet into the box and then hang the box in your plant. These predatory mites like to walk upwards, the only way is up, right? So hang the box low in the plant, but of course close to the pest. You need at least 1 sachet of predatory mites per 1 m2 of plant surface. After 2 weeks you should see a reduction or no mites at all. It is recommended to repeat the treatment after two weeks, especially in case of a large infestation. If this does not solve the problem, it is recommended to increase the dose of predatory mites per m2. Overdosage is not possible.


Are you convinced and do you want to add these saviours to your plants? You can! However, we advise you to use these saviours with your plants immediately after receiving them. If you still want to store the Persi, you can do so for 1-2 days in a dark and ventilated place at 12-14 degrees. Be careful with the sachet, you don't want to damage these saviours by squeezing too hard.

Last but not least!

The persi predatory mites are most effective between 20 and 30 degrees. They also like high humidity. So help these saviours on their way by lightly misting the plants. By the way, please be careful with bright direct sunlight!

Troubled by Thrips? The Amblyseius swirskii (irski) to the rescue!

How do Thrips damage my plants?

Thrips, as well as their eggs or larvae, are often introduced through new plants, clothes or pets. So they can get in really easily. They are not good fliers, but with their short flight they can spread considerably!

Thrips have sucking mouthparts with which they cause the greatest damage to your plants. First, they grate open the cells and actually cause a kind of wound on the leaf or stem. Plant sap comes out of the wound, where the thrips insert their snout and suck out plant sap from the damaged cells. The leaves are eventually so affected that they turn yellow or brown and eventually fall out. Your plant will slowly deteriorate and may even die if you do not control the pest in time. Oh no!


The Amblyseius swirskii (irski) superpowers:

The Amblyseius swirskii is the natural predator of Thrips. They literally eat them raw! These predatory mites are only 0.5 mm in size, so very difficult to see with the naked eye. They eat about 4 thrips larvae a day! If there is nothing left to eat, they will die themselves. Well... this is part of the game. In nature, this is also the way. These rescuers are only interested in your plants, so don't be afraid to find them all over your house.

Amblyseius swirskii

How to use?

You are convinced! You want to use these saviours on your beloved plants. This specially developed breeding sachet contains no less than 250 predatory mites, which can increase to no less than 800 predatory mites that like to eat thrips larvae. This way, your plant is protected for four to six weeks. It is very easy to hang the sachet in your plant and it has a special hole from which the predatory mites can escape. Do not tear the bag! The predatory mites like to walk upwards, so hang the bag a little lower in the plant. This will also protect the sachet from the bright sun. One bag of these rescuers is enough for an area of 1 m2 with plants. They can overflow a little. After 1-2 weeks you should see no more thrips, or at least a reduction. However, it is advisable to repeat the treatment after a month, especially in case of a large infestation. If this does not solve the problem, it is advisable to increase the dose of predatory mites per m2.


Very interesting that these little critters can be the saviours of your plant, isn't it? If you choose to try this out, we would like to give you these tips. After receiving these irski, we recommend you to use them right away. If you still want to keep them, you can do so for 1-2 days at the latest in a dark, ventilated place at 12-14 °C. In order not to damage the irski, it is advisable to hold the sachet by the piece of cardboard.

Last but not least!

Finally, we would like to inform you that it is important that the room in which the plant is placed (where the irski will be hung) is not too cold. The irski is most effective in warm temperatures of up to 32 °C. They also like high humidity. You can therefore help these saviours by lightly misting the plant(s).

Insect Heroes

We are proud to work together with Insect Heroes to make you and your plants happy. Insect Heroes (part of Bestico) consists of an enthusiastic team of experts in the field of biological pest control. The mission of Insect Heroes is: gardens, balconies, hobby greenhouses and houseplants without poison.

After all, isn't it crazy that we use pesticides when there are so many natural alternatives? The superheroes we now sell together with Insect Heroes are very small, but that doesn't mean they don't have powerful super powers! Let these beautiful creatures protect your plants!


Emma is a botanical enthusiast with an unwavering desire to share her extensive knowledge about plants with you. She's always delighted to answer your questions, provide care tips, and guide you to find the perfect plant for your space.

March 31, 2022
Hi, I'm Emma, your guide!

Hi, I’m Emma, your guide!