Biological pest control is one of the most effective strategies for keeping a hydroponic or greenhouse grow pest-free, but there’s just one problem. Buying predatory mites repeatedly gets expensive. Whether you’re growing leafy greens, ornamentals, fruiting vegetables, or managing a large-scale farm, the cost of continual reapplication can really stack up.

Fortunately, there’s a proven technique that allows you to multiply the predatory mites you already purchased — giving you a continuous supply of beneficial insects for a fraction of the cost.

This method works for small hobbyists, commercial growers, and even large-scale agriculture, and it only requires a few inexpensive materials. Let’s break down exactly how to do it.

Why Predatory Mites Are So Valuable in Hydroponics

Predatory mites are frontline defenders against pests like:

• Spider mites
• Thrips
• Aphids
• Fungus gnats
• Root aphids
• Other pest mite species

Different varieties thrive in different conditions. Some live in soil, others live on foliage or flowers, and many have temperature/humidity constraints. Selecting the right species for your crop is crucial.

But here’s the part most growers don’t realize:

The predatory mites you buy aren’t feeding on bran or pollen in the container, they’re feeding on another species of mite living in the substrate.
Those “food mites” (sometimes called detritivore or flour mites) can be cultured easily, and they’re the key to creating your own renewable source of predatory mites.

The Core Concept: Grow Their Food → Grow Your Predators

Predatory mites come packaged with a substrate (usually bran or vermiculite) containing:

• Predatory mites (your biocontrol species)
• Detritivore mites (their food source)
• Bran or pollen (food for the detritivore mites)

By giving the detritivore mites more bran or pollen in a controlled container, they multiply rapidly. The predatory mites follow suit, because their food source is increasing.

With this method, you can:

• Stretch one bottle of predatory mites into months of supply
• Maintain a steady population in your grow
• Completely avoid buying additional mites during the season
• Dramatically reduce pesticide and biopesticide use
• Improve overall crop health and stability

How to Culture Predatory Mites: Step-by-Step

1. Buy a Bag of Untreated Animal-Grade Bran

Go to a farm supply or animal feed store, but NOT a supermarket.
Human food-grade bran contains preservatives that prevent mites from feeding, making it useless for culturing.

A 25 kg bag usually costs around £20/$25/€25.

Store it dry and away from your grow space or kitchen; these mites will infest any carbohydrate-based food if allowed.

2. Prepare a Culture Container

Choose a small airtight tub or jar.
Size guideline:
Use a container about 4× the volume of the original predatory mite packaging.

No need for air holes, you’ll open it occasionally.

Fill the container with a few scoops of bran.

Add a tiny amount of moisture, just enough to keep it from becoming bone-dry, but not enough to encourage fungal growth.

3. Seed the Culture

Add 20% of your purchased predatory mites (including the substrate they came in) into the bran.

Apply the remaining 80% to your plants as normal.

Close the lid and label your new culture.

4. Let the Population Multiply

Keep the culture warm, dry, and away from food storage areas.

Over time:

• The detritivore mites eat the bran and multiply rapidly
• The predatory mites eat the detritivore mites
• Both populations increase in number

You may notice:

• Decomposition of bran
• Mite movement visible on the surface
• A “dusty” appearance as mites proliferate

If you have a microscope or hand lens, monitoring is even easier.

5. Harvest and Reseed

Once the population is high:

1. Use 80% in your grow area
2. Save 20% to inoculate another container of fresh bran

Repeat indefinitely — you now have sustainable biocontrol.

What Not to Do

Avoid these common mistakes:

❌ Do NOT bring the whole 25 kg bag into your grow room

It will become completely infested — causing mite explosions everywhere.

❌ Do NOT store cultures near food

Bran, flour, rice, cereal, pasta — all are mite magnets.

❌ Do NOT allow fungal growth

Too much moisture ruins the culture.

Can Soil-Dwelling Predatory Mites Be Cultured Too?

Yes — it’s trickier, but possible.

For mites like Stratiolaelaps scimitus (formerly Hypoaspis), you can mix bran into coco coir. The detritivore mites eat the bran, and the soil mites feed on them.

This approach works extremely well for preventing:

• Fungus gnats
• Root aphids
• Soil-borne pest mites

Why This Hack Matters (Especially for Large-Scale Growers)

Biocontrol companies charge significant premiums for predatory mites because greenhouse growers must buy them repeatedly.

That’s why:

• Large farms rarely use mite biocontrol
• Greenhouse growers struggle with ongoing costs
• Many operations fall back on chemical pesticides

With this method, even a large farm could scale to 100 kg of bran and manage greenhouse or orchard mite pests at a fraction of the cost.

What About Other Beneficial Insects?

This DIY method works brilliantly for mites, but not for beneficials with complex life cycles.

Hard-to-culture species include:

• Ladybirds (delicate, high mortality)
• Lacewings
• Hoverflies

Mites, however, are simple, hardy, and reproduce fast; perfect for this approach.

Final Thoughts

This mite-culturing hack is one of the most powerful cost-saving tricks in hydroponics and horticulture. With nothing more than a bag of bran and a container, you can:

• Reduce pesticide use
• Maintain a constant biocontrol population
• Save hundreds or thousands per season
• Improve plant health and resilience

If you’ve tried this method, or have your own biocontrol hacks, feel free to share your experience!

Article by Dr Russell Sharp

If you would like to keep up to date with subjects just like this, you can listen to both our podcasts! Links can be found bellow:

Hydroponics Daily Podcast: https://podcasts.apple.com/us/podcast/hydroponics-daily/id1788172771

Cereal Killers Podcast: https://podcasts.apple.com/us/podcast/cereal-killers/id1695783663