Beneficial Insects for Cannabis: Biologically Control Fungus Gnats, Thrips, Spider Mites & More

Pests are among the problems that can develop from a minor anomaly into a serious infestation in a cannabis grow within a short time. Fungus gnats, thrips and spider mites often find favorable conditions, especially in warm indoor setups.

Chemical plant protection products are not the only option. With carefully selected beneficial organisms, many common cannabis pests can be controlled biologically.

However, the key is to use the right beneficial organism against the right pest.

In this overview, we explain which beneficial organisms are suitable for cannabis, which pests they are used against and what you should keep in mind when applying them.

What are beneficial organisms?

Beneficial organisms are organisms that use certain plant pests as natural prey or hosts.

These include, for example:

• Predatory mites
• Nematodes
• Lacewings
• Parasitic wasps
• Predatory bugs
• Ladybirds

In a cannabis grow, beneficial organisms that are easy to apply and can be used specifically against common indoor pests are particularly interesting.

The major advantage: Instead of treating the entire plant with a product, you use a natural antagonist of the respective pest.

Which beneficial organisms are suitable for cannabis?

Not every beneficial organism works against every pest.

The most important beneficial organisms can be assigned relatively easily to the most common problems in a cannabis grow:

Every successful biological pest control strategy therefore begins with a question:

Which pest do I actually have?

A beneficial organism against spider mites, for example, will not automatically help with a fungus gnat problem.

SF nematodes against fungus gnats

Fungus gnats are among the most common pests in an indoor grow.

The small black flies are usually first seen around the substrate or during watering. However, the actual problem is not in the air but in the soil.

This is where fungus gnat larvae live.

This is precisely where SF nematodes of the species Steinernema feltiae are used.

The microscopic nematodes are applied with the irrigation water and thereby reach the moist substrate directly. There, they actively search for fungus gnat larvae.

Yellow sticky traps and nematodes serve different purposes:

Yellow sticky traps reduce or monitor adult fungus gnats. SF nematodes, on the other hand, target the larvae in the substrate.

The larval population is therefore particularly important for sustainable control.

SF nematodes at CannaSelection®

Our SF nematodes are available in different sizes for small and larger plant populations:

5 million SF nematodes

10 million SF nematodes

20 million SF nematodes

This allows you to select the required quantity according to the number of plants or the substrate area.

View product: SF nematodes against fungus gnats

Cucumeris predatory mites against thrips

Thrips are also a classic problem in an indoor cannabis grow.

Typical signs may include pale or silvery feeding damage on the leaves as well as small dark fecal spots.

Cucumeris predatory mites can be used for the biological control of young thrips larvae.

Neoseiulus cucumeris moves actively across the plant and searches for suitable prey.

So-called breeding sachets are particularly practical.

They are hung directly on the plant. The predatory mites gradually leave the sachets and spread throughout the plant population.

This means no complex mixing or spraying is required.

Cucumeris at CannaSelection®

We offer the predatory mites in different quantities:

3 breeding sachets

5 breeding sachets

10 breeding sachets

As a simple guideline, you can start with one sachet per plant. For particularly large plants or heavier infestations, a higher stocking density may be useful.

View product: Cucumeris predatory mites against thrips

Californicus predatory mites against spider mites

Spider mites can reproduce very quickly under warm conditions.

Indoor grows in particular often provide constant temperatures that allow an initially small infestation to spread quickly.

One natural antagonist is the predatory mite Neoseiulus californicus.

Californicus predatory mites move across the plant and actively search for spider mites.

Here too, we rely on practical breeding sachets that are hung directly in the plant population.

This makes application particularly easy while also enabling the continuous release of predatory mites onto the plants.

Californicus at CannaSelection®

Available are:

3 breeding sachets

5 breeding sachets

10 breeding sachets

This covers both smaller homegrow setups and larger plant populations.

View product: Californicus predatory mites against spider mites

Lacewings against aphids and mealybugs

Lacewings are among the most versatile beneficial organisms used in biological plant protection.

The larval stage is particularly interesting.

Lacewing larvae of the species Chrysoperla carnea actively search for small soft-bodied prey.

These include in particular:

• Aphids
• Mealybugs
• Scale insects

The larvae move independently across the plants and can also reach areas such as the undersides of leaves and young shoots.

Our lacewings are applied using practical cards. These are hung directly within the plant or as close as possible to the infested area.

Lacewings at CannaSelection®

Available are:

3 lacewing cards

5 lacewing cards

10 lacewing cards

This allows the number of beneficial organisms to be adjusted to the size of the plant population.

View product: Lacewings against aphids and mealybugs

Which beneficial organism helps against which cannabis pest?

If you already know which pest is present, the choice is relatively straightforward.

Fungus gnats

Recommendation: SF nematodes

The treatment is applied through the substrate and targets the larvae.

Thrips

Recommendation: Cucumeris predatory mites

The predatory mites are used directly within the plant and specifically search for young thrips larvae.

Spider mites

Recommendation: Californicus predatory mites

Californicus is particularly suitable for the biological control of spider mites in the plant population.

Aphids

Recommendation: Lacewing larvae

The larvae actively search for aphids and other suitable prey.

Mealybugs and scale insects

Recommendation: Lacewing larvae

Lacewing larvae can also be used against these soft-bodied pests.

Should beneficial organisms be used preventively or only when an infestation occurs?

An important distinction must be made between an acute pest infestation and preventive use.

Some beneficial organisms can be introduced when a plant population is particularly at risk or when certain pests regularly cause problems.

In the case of an already severe infestation, a higher number or repeated application may be required.

As a general rule:

The earlier a pest problem is detected, the easier it is to control biologically.

That is why it is worth checking plants regularly.

Particularly important areas are:

Undersides of leaves

Young shoots

Substrate surface

Areas between the leaf and stem

Noticeable leaf discoloration or feeding damage

Beneficial organisms and Living Soil

Beneficial organisms are particularly well suited to a biologically oriented grow.

Living Soil is based on keeping biological processes in the substrate as active as possible and building a functioning soil ecosystem.

Instead of immediately intervening with a broad-spectrum plant protection product whenever a problem arises, you can work specifically with natural antagonists.

This has another advantage:

Many conventional sprays can affect not only pests but also beneficial organisms that have already been introduced.

Anyone working with beneficial organisms should therefore always check which plant protection products were used previously and whether they are compatible with the respective beneficial organism.

Creating the right conditions for beneficial organisms

Beneficial organisms are living organisms.

Their activity therefore depends on the conditions in the grow.

Particularly relevant are:

Temperature

Every beneficial organism species has a preferred temperature range. Typical indoor temperatures are well suited to many common predatory mites and lacewings.

Humidity

Predatory mites in particular benefit from sufficient moisture in the plant’s microclimate.

Substrate moisture

SF nematodes require a sufficiently moist substrate so that they can move through it.

Infestation severity

In the case of a very severe pest infestation, a single application may not be sufficient.

Plant protection products

Certain products can harm beneficial organisms or make their use considerably more difficult.

We will cover these points in more detail in our upcoming guides on the individual beneficial organisms.

Ordering and applying beneficial organisms correctly

Unlike fertilizers or substrates, beneficial organisms are living products.

They should therefore not be stored unnecessarily long.

Our beneficial organisms are freshly prepared for shipping and dispatched directly from Germany.

After receiving them, you should use them as soon as possible in accordance with the respective application instructions.

To avoid unnecessary storage times during transport, live beneficial organisms are generally shipped in a way that minimizes extended weekend stays within the parcel network.

In extremely high or low temperatures, it may be advisable to temporarily adjust shipping to protect the organisms.

Beneficial organisms or chemical pest control?

Beneficial organisms are not a universal solution for every pest problem.

Their major advantage lies instead in their specificity.

The appropriate beneficial organism is specifically used against a particular pest.

This can be especially interesting for cannabis, as broad-scale treatment of plants with sprays is often best avoided.

Beneficial organisms can therefore be an important part of a holistic plant protection strategy.

This also includes:

Regular plant inspections

Clean grow environment

Early detection of an infestation

Quarantine of new plants or cuttings

Yellow or blue sticky traps for monitoring

Suitable temperature and humidity

Targeted use of suitable beneficial organisms

Conclusion: The right beneficial organism for the right pest

Biological pest control in a cannabis grow does not have to be complicated.

The first key step is to correctly identify the pest.

You can then select the appropriate natural antagonist:

Fungus gnats: SF nematodes

Thrips: Cucumeris predatory mites

Spider mites: Californicus predatory mites

Aphids: Lacewing larvae

Mealybugs and scale insects: Lacewing larvae

This basic principle can be used to address many of the most common pest problems in an indoor grow in a targeted biological way.

In our beneficial organism range, you will find suitable packs for small and larger plant populations.

Discover beneficial organisms

Frequently asked questions about beneficial organisms for cannabis

Are beneficial organisms suitable for cannabis?

Yes. Various beneficial organisms are used in biological plant protection and can also be used specifically against suitable pests on cannabis. Correctly selecting the beneficial organism is crucial.

Which beneficial organisms help against fungus gnats?

SF nematodes of the species Steinernema feltiae are used against fungus gnat larvae living in the substrate.

Which predatory mites help against thrips?

Cucumeris, or Neoseiulus cucumeris, is used particularly against young thrips larvae.

Which predatory mites help against spider mites?

Neoseiulus californicus is a natural antagonist of spider mites and is suitable, among other applications, for warm indoor conditions.

Which beneficial organisms help against aphids?

Lacewing larvae are versatile predators and can be used, among other applications, against aphids.

Can I use different beneficial organisms at the same time?

Depending on the pest situation, different beneficial organisms can be used within a plant population. It is crucial that the species and their requirements are compatible with one another.

Can I use beneficial organisms preventively?

Certain beneficial organisms or breeding sachets are also suitable for early or preventive use. The options vary depending on the species.

How long can I store beneficial organisms?

Beneficial organisms are living organisms and are generally not conventional storage products. They should be used as soon as possible after receipt and stored according to the respective product instructions until then.