Trick or treatment: the good bugs behind healthy plants.

It's the season of plastic spiders and fake cobwebs. Insects get a bad reputation this time of year.

In the plant world, though, some of the most important work is done by creatures so small you'll never notice them. They're called beneficial insects, and they're one of the reasons healthy plants stay healthy.

What are beneficial insects?

Beneficial insects are the natural predators of plant pests. Almost every pest has something that eats it. Ladybugs eat aphids. Predatory mites eat spider mites. Growers have used this balance for decades to protect plants without relying on chemical sprays.

The term is used loosely. Not all of them are technically insects: mites are closer relatives of spiders, and nematodes are microscopic roundworms. What they share is a job. They keep pest populations in check, and they leave everything else alone.

Today, this is standard practice in professional horticulture. In the Netherlands, where many of Europe's indoor plants are grown, biological pest control was used in 94% of greenhouse cultivation in 2024. Our own main supplier has moved its greenhouses toward biological pest control, using biological methods as much as possible and chemical treatments as little as possible.

Why it matters

Our approach to plant health starts with one idea: the most sustainable thing we can do is keep the plants alive.

Chemical sprays work against that over time. They leave residues in spaces where people work, eat lunch, and sometimes bring their dogs. They also don't discriminate. The same product that kills a pest kills the natural predators that would have kept it in check, sometimes for weeks afterward. Once you start spraying, you're often stuck doing it.

Beneficial insects work with the plant instead. That's why biological control is our first choice and chemical pesticides are our last resort, reserved for severe cases. Four people on our team hold the Sachkundenachweis, Germany's certificate of competence for plant-protection products, and only they can apply them.

It matters for what happens next, too. Our plants and substrate circulate between member offices. When a plant is cycled out, we rehab it in our warehouse so it can be reused or rehomed. Substrate is cleaned and reused, and only discarded when pests or disease leave no other option. A plant that has been cared for gently has a second life ahead of it.

Meet the good guys

Nematodes (Steinernema feltiae) are microscopic roundworms, around 0.8 mm long. They live in moist soil and hunt the larvae of fungus gnats, the tiny black flies you sometimes see around plant pots. Within one to two weeks, they break the gnats' breeding cycle. Koppert, one of the leading producers of beneficial organisms, describes them as safe for people, plants, and other beneficial insects. They're the beneficial we rely on most.

Predatory mites (Neoseiulus californicus) feed on spider mites and young thrips. They're barely visible to the naked eye and stay on the leaves, where their food is.

Lacewing larvae (Chrysoperla carnea) are aphid specialists. A single larva can eat several hundred aphids before it pupates.

Australian ladybugs (Cryptolaemus montrouzieri) feed on mealybugs. They're visible and they fly, so they stay in our warehouse.

What it looks like in your office

Mostly, nothing. Prevention does most of the work: the right plant in the right spot, the right amount of water, and a Plant Expert who checks every plant on regular care visits for our members.

If a treatment is needed, it's targeted and quiet. Nematodes, for example, are simply watered into the soil. Nothing flies around, nothing crawls out of the pot, and most people never know it happened.

Scary names, harmless bugs

Plant pests have terrible PR. The names sound like something out of a horror film. The reality is much smaller, slower, and far less interested in you.

Spider mites aren't spiders. They're tiny plant-feeding mites, about the size of a full stop, named for the fine webbing they leave on leaves.

Mealybugs look like small tufts of cotton tucked into leaf joints. They move slowly, if at all.

Fungus gnats are small flies drawn to damp soil. They don't bite, and they're not interested in people, food, or desks.

Thrips, aphids, and scale insects are all sap feeders, most just a few millimeters long.

None of these are hygiene problems, and none of them live on people. A few thrips on a plant is not an office infestation. It's a plant that needs a care visit.

How to prevent pests on office plants

Pests don't start in the plant. They arrive, on a plant brought in from home, a bouquet on the reception desk, or a jacket that brushed past a balcony garden. Warm, dry, heated air in winter also suits spider mites, and soil that stays wet too long suits fungus gnats.

• Check with us before adding plants. Plants from home or the garden center are one of the easiest ways for pests to enter a shared space.
• Tell your Plant Expert early, and skip the DIY spray. A small issue is easy to treat. Store-bought sprays can harm the natural balance we work to keep. More on everyday care in our plant care guide.

The scariest thing in your office this month

Probably not the plants.

If you're a member and you've spotted little flies or something sticky on a leaf, message your Plant Expert. If you're not yet a member, book a chat or write to us at hello@plantclub.io. We'll take it from there.