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How to fight fungus gnats on orchids

June 10, 2020

Growers often find the larvae of fungus gnats on orchids. This article covers the harm they can cause and how choosing the right growing media might help you prevent plant loss.

Little mosquito-like flies cause a common issue in the propagation and cultivation of phalaenopsis plants. The larvae of these flies are known as “pot worms” and can affect the plant roots if present in large numbers. Continue reading to learn a little more about fungus gnats on orchids and the measures we take to make sure your orchid growing media are free of them. We also included a couple things a grower can do to reduce the presence of the larvae.

What is know about fungus gnats on orchids?

Pot worms are the larvae of the lyprauta spp. and some other mosquitoes part of the fungus gnat species. These little flies aren’t much of an issue when they are all grown up, it’s the larvae that cause the trouble for phalaenopsis growers. The flies have relatively short lifespans, which means they procreate rapidly and can all of a sudden be present in big numbers. The grown fly lays her eggs in growing media. After some time worms emerge from the eggs and make their way through the growing medium. They leave behind an acidic slime trail.

They feast on new root tips, leaving bite marks and eroded roots behind. The orchids usually respond by creating fresh roots sprouting slightly above the affected tips.

As a result growth retardation occurs, because plants focus their energy on producing new root tips. In addition the orchids have trouble taking up water and nutrients because of the affected roots. Seeing that this mainly takes place during the early stages of cultivation this can cause serious plant deficiencies or loss.

Orchid growing media free of pests

One of the main things to do to prevent plant loss due to pot worms is making sure you buy plant material and growing media free of contamination. We take great care ensuring our orchid growing media are save to use and we are even looking for ways to help fight the pot worms through growing media.

The bark we use in our orchid growing media is steam-treated and heated to well over 160℉ before it is shipped to our production sites. Once we have blended it into an orchid mixture we move it to our heating cells, where both the external and core temperatures rise. We keep the mixture stored in these cells until shipment to make sure nog larvae, eggs or mosquitoes survived. This way our customers can be entirely sure their orchid growing media is free of contamination. Have a look at our growing media for orchids here.

Trials have shown pot worms prefer moist cultivation methods. This means they are found less in dryer cultivation methods. We can help orchid growers determine the best growing medium composition in order to switch to dryer methods and even advice on growing methods in general.

How to control the fungus gnat population

In general there’s a lot to say for keeping a tidy business. This may also benefit you when you try to reduce the amount of pot worms in your greenhouse. Make sure to remove discarded plant material and growing media and try to keep the presence of algae to a minimum as well.

In addition you might also want to look into biological control of these little pests. However, studies show these methods aren’t always effective and can only help a little. There are several natural enemies available that could help you to slightly weaken the pot worm population without harming the plants. Some examples are parasitic wasps, hunter flies and predatory mites.


Lyprauta larvae will probably continue to be a problem in phalaenopsis propagation for quite some years to come. In any case, we are conducting reserach into new ways to help growers fight these pests throug growing media. Ask our team if you would like to know more about this issue or would like to get an offerfor orchid growing media for your company!