The appearance of insects in growing rooms or anywhere on the farm is a threat to your crop, your reputation, and the overall sanitary conditions of the facility.
But it’s important to remember: dealing with pests is much harder than preventing them from showing up in the first place.
📌By the way, a description of all these pests is in a separate article.
Regular preventative treatments should become part of your standard farm routine.
Even if you don’t see fungus gnats, flies, or beetles right now, that doesn’t mean they won’t appear next week. Mushroom spores, leftover substrate, and high humidity create perfect conditions for insect reproduction.
Insects can get in through ventilation openings, gaps, open doors, equipment, packaging — or even hitch a ride with your staff.
And if they’ve already laid eggs somewhere, a temporary fix won’t solve the problem — the pests will keep coming back.
Prevention starts with monitoring. Install sticky traps in your fruiting rooms and incubation areas.
💡These will help you identify what kind of insects are present and where they are most active.
Preventative insecticide treatments should be done between growing cycles, when rooms are empty. Most insecticides cannot be used around active crops.
Most insect pests and their larvae hide in places where it’s damp, there’s organic waste, and air doesn’t circulate well.
One of the biggest hotspots is your spent substrate storage area.
💡Decomposing substrate — like any organic or food waste — gives off odors that attract insects.
Storing used blocks in bags under a shed or indoors is not enough: a single bag can house an entire insect colony.
These pests can quickly spread to your fresh blocks during the first days of incubation. The photo shows orange larvae under the film in oyster mushroom blocks.
There’s no point adding chemicals to the substrate to stop insects from laying eggs — what matters is proper substrate pasteurization and processing.
📌Read on the production of substrates.
Wet spots inside the block are ideal for mold and bacteria, and their smell attracts pests looking for a place to reproduce.
📌You can learn more about substrate disposal in a separate article.
Also check:
▶️ Gaps between the floor and walls, especially if they’re unsealed
▶️ Ventilation ducts without screens or with damaged filters
▶️ Trays and corners where moisture and mycelium debris collect
▶️ Packaging or tool storage areas, especially if they contain damp cardboard
▶️ Rubber door seals and plastic joints where spores and larvae can accumulate
Larvae can survive in micro-environments with just a bit of moisture. Even a thin layer of organic buildup on plastic film or walls can become an egg-laying site.
The worst part? Insects often reproduce quietly at first — you don’t see them until they’re already moving into your growing rooms. And by the time you do notice, the population is usually starting to explode.
First, remove any damaged or aging blocks. These are the most likely sources of infestation.
Check all seals, cracks, the ceiling above blocks, and the humidifier area — even hoses and pipes can harbor larvae.
If possible at that stage of your growing cycle, reduce humidity. Dry air slows larval development.
Consider using electric insect traps or “bug zapper” lights — make sure the model is rated for use in humid conditions.
Most importantly, you won’t get rid of the insects unless you cut off their access to food and moisture.
So along with treatments, investigate where those resources are coming from.
But what if you already have mushrooms in the room? Read on.👇
On mushroom farms, not every effective insecticide is appropriate for your setup. Choose your treatment carefully, based on these key principles:
The product should be approved for use in food production facilities or greenhouses. That means it has clear instructions, designated zones (empty room, growing area, etc.), and a “pre-harvest interval” — the time that must pass between application and harvesting.
If a product doesn’t provide this information, don’t use it.
Some countries only allow the use of biological products, so always check local regulations.
For cleaning and preventative use in empty rooms, common options include:
✅ First stage: Disinfecting fogs or aerosols (often based on quaternary ammonium compounds — QACs)
✅Second stage: Short-acting insecticide sprays plus surface treatments that remain active for hours or days
Before using any of these, ask your supplier whether they can be combined. Usually — they can’t. Always follow professional advice.
Different classes of insecticides work in different ways. Some have ovicidal action (they kill insect eggs), others are larvicides (they target larvae).
There are also acaricides — these are specifically for mites.
💡If you see tiny reddish bugs on your blocks, chances are it’s red spider mites, not beetles, and you’ll need an acaricide.
In my country, the most commonly used active ingredients are found in products like Actara, Actellic, Arrivo, Fastac, and Decis.
If you can’t find those brands, look up the active ingredients — many have international analogs under different names.
💡Note: insects develop resistance to these products over time. It’s essential to rotate chemical classes. For example, after a pyrethroid, switch to a phosphor-organic (OP) product, then to a neonicotinoid, and then back to another pyrethroid.
Before applying any treatment:
▶️ Remove all fresh blocks and harvestable mushrooms from the area
▶️ Ventilate thoroughly after treatment
▶️ Wear personal protective equipment
▶️ Test any new product in a single room before full application
If small gnats are sitting directly on mushroom clusters ready for harvest, your best bet is to lure them away.
You can try products that combine thiamethoxam (an insecticide found in products like Actara) with the fly sex pheromone Z-9-tricosene. This pheromone mimics the smell of a female and strongly attracts many flying insects, including fungus gnats.
Some countries sell ready-to-use bait formulas combining both ingredients.
In mine, it’s sold as Agita — but trade names vary. Always check if the product is approved for use in mushroom-growing spaces.
💡Important: never spray this bait — it should not touch the mushrooms.
Instead, dilute it according to the label, and apply with a brush to the lower part of the block film — away from any fruiting bodies.
The smell attracts insects, and they leave the mushrooms to land on the baited spot.
You can also soak a strip of parchment paper in the bait solution and hang it near the blocks — as long as it’s safe and clearly described in the product’s instructions.
Periodic preventative treatments in empty rooms and good hygiene are much safer than trying to fight a full-blown infestation. Insects spread quickly in mushroom facilities.
Don’t skip prevention!
