If you grow cannabis long enough, eventually something is going to try to eat it; spider mites show up uninvited, aphids discover your plants and apparently tell all their friends, and fungus gnats have an uncanny ability to materialize the second your soil stays wet for approximately seventeen minutes too long.

This is part of growing plants. You can have the cleanest grow room in the world, inspect everything that comes through the door, and generally behave like a person who has their life together, and pests can still find a way in (this is a life lesson I’ve still yet to fully learn, but hey, you’re reading this).

The good news is that you don’t necessarily have to respond by spraying everything that moves. Sometimes the best solution to having too many bugs is, strangely enough, introducing more bugs.

I’m talking about beneficial insects: predators and other organisms that help keep pest populations under control. They’re basically the tiny hired security guards of your cannabis garden, except you pay them once and they immediately start eating the trespassers.

So, let’s talk about which beneficial insects are actually useful, what they eat, and how to make them part of a sensible pest-management strategy.

Beneficial insects are exactly what the name suggests: insects that provide some kind of benefit to your garden instead of treating your cannabis like lunch. In cultivation, we’re usually talking about predators or parasitoids that attack common pests such as aphids, spider mites, thrips, whiteflies, fungus gnats, and other unwanted visitors.

Ladybugs, green lacewings, rove beetles, and parasitic wasps are some of the more common examples. You’ll also frequently hear predatory mites and beneficial nematodes (e.g. Microscopic roundworms that live in the soil or inside plant tissue, where certain species can become tiny little freeloaders that feed on your plants and cause all sorts of problems.) included in the conversation, although technically mites are arachnids and nematodes are roundworms.

“Beneficial insects” is simply easier than saying “beneficial insects, arachnids, nematodes, and assorted tiny creatures we’re paying to murder other tiny creatures,” so we’re sticking with it for this conversation!

The big advantage here is that you’re using biology to manage biology. Instead of repeatedly applying something to kill pests, you’re introducing predators that actively search for them – little “T1000’s”. That doesn’t mean beneficial insects are magical. You can’t throw a container of ladybugs into a completely infested grow, go play FIFA for three weeks, and come back expecting everything to be perfect. They work best when they’re part of a larger pest-management system.

And before you introduce anything, you need to know what you’re fighting. 

One of the biggest mistakes growers make is seeing plant damage, deciding it must be a particular pest, and immediately treating for it. The problem is that a lot of cannabis problems look similar at first glance. Yellowing, curling, spots, slow growth, and general plant misery can have several causes.

So inspect your plants before doing anything dramatic. Look underneath the leaves, around stems, near new growth, and across the surface of your growing medium. If you’re dealing with something microscopic like russet mites, grab some magnification.

Spider mites are among the more infamous cannabis pests. They’re extremely small, feed on plant tissue, reproduce quickly, and may eventually produce visible webbing when populations become large. Growers often notice stippling or tiny pale spots on leaves before the problem becomes obvious.

Aphids are easier to see. They’re small, soft-bodied insects that tend to cluster around leaves and stems while sucking sap from the plant. They can cause curling, yellowing, and wilting, and they produce a sticky substance called honeydew that can encourage sooty mold.

Whiteflies also feed on plant sap and usually hang around the undersides of leaves. Fungus gnats are those annoying little dark flies that hover around moist growing media, while their larvae live below the surface. Thrips scrape plant tissue and can leave behind silver or bronze-looking damage.

Then you’ve got caterpillars chewing holes through leaves and flowers, mealybugs looking like somebody glued tiny pieces of cotton to your plants, root aphids attacking below the soil line, and russet mites being microscopic assholes that can cause distorted growth before you even realize they’re there.

The point isn’t to memorize every pest in existence. The point is to identify the problem before choosing the solution. You wouldn’t call a plumber because your transmission fell out; so, don’t release 2,000 ladybugs because you saw something weird on a leaf.

There isn’t one “best” beneficial insect because different predators specialize in different prey. The right question is, “What’s the best beneficial insect for the pest I have?

For cannabis growers, three of the most useful and recognizable options are ladybugs, predatory mites, and green lacewings. Depending on the situation, growers may also use rove beetles, beneficial nematodes, parasitic wasps, or other specialized biological controls.

Let’s start with the celebrity.

Ladybugs have somehow managed to become one of the few predators humans collectively decided were adorable. They’re colorful, harmless to us, and spend their time eating other insects alive.

Excellent public relations department. Ladybugs are particularly well known for eating aphids. Both adults and larvae are predators, making them useful when aphid populations start appearing throughout a garden.

There is one rather obvious problem with using adult ladybugs, though: they can fly.

You can purchase a ridiculous number of ladybugs, carefully release them into your garden, tell them they’re part of the family now, and discover the following morning that half of them have relocated to wherever ladybugs go when they decide your garden isn’t good enough.

Providing water, shelter, and appropriate habitat can help encourage them to remain, and releasing them close to an active food source gives them an immediate reason to start feeding.

But the important thing is to monitor the pest population afterward. Don’t judge whether the treatment worked by how many ladybugs you released. Judge it by whether you still have an aphid problem.

If you’ve never experienced a serious spider mite infestation, I’d recommend keeping it that way.

Spider mites are tiny, reproduce quickly, and have a wonderful habit of going from “I think I saw something underneath this leaf” to “Why does my plant look like Halloween decorations?” remarkably fast.

Fortunately, there are mites that eat other mites. Predatory mites feed on pest mites and, depending on the species, may also target thrips or other tiny arthropods. They don’t feed on your cannabis plants, which makes them useful biological-control agents.

The catch is that there are several species of predatory mites, and they’re not interchangeable. Different species prefer different prey, temperatures, humidity levels, and environmental conditions.

That means you shouldn’t simply search “predatory mites for weed,” order whatever has the coolest-looking package, and start throwing them around the grow room. Figure out what pest you have first. Then choose a predator that actually hunts it and can survive in your growing environment.

This is pest management, not Pokémon. You don’t need to collect them all.

Adult green lacewings are beautiful little insects with translucent wings and delicate bodies. They look like something that should spend its afternoon sitting peacefully on a flower.

Their children are lunatics. Green lacewing larvae are commonly called aphid lions, and that nickname exists for a reason. They’re aggressive predators that feed on aphids, thrips, insect eggs, small caterpillars, and various other soft-bodied pests.

That makes lacewings particularly interesting because they’re not limited to one enemy.

Adult lacewings may feed on nectar, pollen, and honeydew rather than spending all day hunting pests, so flowering plants can help make an outdoor or greenhouse garden more attractive to them. Plants such as dill, fennel, and cilantro can provide food sources for adults. This introduces an important concept that applies to beneficial insects generally: if you want them to stick around, you need to give them somewhere worth living.

Once you start thinking about beneficial insects, you quickly realize that a cannabis garden isn’t just cannabis plants sitting in dirt.

It’s an ecosystem.

You’ve got plants, predators, prey, microorganisms, fungi, soil organisms, moisture, temperature, airflow, and approximately 47 other variables you’re going to become obsessed with after deciding growing cannabis would be a relaxing hobby.

The goal isn’t necessarily to create a completely sterile environment where nothing except cannabis is allowed to exist. The goal is balance, and that’s where Integrated Pest Management comes in.

Integrated Pest Management (IPM) is basically the grown-up version of pest control.

Instead of waiting until something goes wrong and then spraying whatever bottle happens to be closest, IPM combines prevention, monitoring, environmental management, biological controls, physical controls, and targeted treatments when they’re genuinely necessary.

The idea is to prevent pest populations from becoming serious enough that you’re forced into increasingly aggressive interventions, and the first part of that is incredibly boring: just keep your freaking grow clean. I know. Revolutionary stuff.

But prevention works. New clones, plants, growing media, tools, containers, clothing, and equipment can all potentially introduce pests into a cultivation environment.

Clones deserve special attention because a perfectly healthy-looking clone can essentially be a Trojan horse with fan leaves. Inspect new plants carefully and quarantine them when appropriate before introducing them to the rest of your grow. A few minutes spent inspecting a new plant is much more enjoyable than spending the next month staring through a loupe wondering whether a microscopic dot just moved.

• Regular scouting is one of the simplest things you can do for pest control.
• Don’t just admire the top of the canopy and congratulate yourself.
• Turn leaves over.
• Look at stems.
• Inspect new growth.
• Check the growing medium.
• Pay attention to anything that suddenly looks different.
• Sticky monitoring cards can also help reveal populations of flying pests before they become obvious throughout the garden.
• The goal isn’t to become paranoid every time you see something move. You’re learning what normal looks like.
• Once you know what your healthy garden normally looks like, unusual changes become much easier to spot.
• And the earlier you find a pest, the easier your life generally becomes.

Sometimes growers become so focused on killing a pest that they forget to ask why the pest population exploded in the first place. Your environment matters.

Temperature, humidity, moisture, airflow, plant density, and sanitation can all influence pest populations. 

Fungus gnats are an easy example. They love moist growing media. If your plants are sitting in constantly saturated soil, buying increasingly elaborate fungus gnat weapons without addressing your watering practices is missing part of the problem.

Dense foliage can also make it harder to inspect plants and may create sheltered areas where pests can establish themselves.

This is one of those annoying cultivation lessons that keeps appearing everywhere: fixing the underlying environment is usually more useful than endlessly treating the symptom.

Here’s a surprisingly common biological-control mistake: a grower discovers pests and releases beneficial insects, then discovers more pests, sprays something, and suddenly wonders where all those beneficial insects went.

You can probably see where this went wrong. Even products marketed as natural or organic can affect beneficial organisms because “organic” does not mean the product somehow recognizes which bugs you paid for and politely avoids them. If you’re using beneficial insects, always consider how another pest-control product might affect them before applying it. Sometimes treatment is necessary.

Severe infestations happen, and biological control isn’t guaranteed to solve every problem. Just make sure you’re not accidentally firing your security team while the burglars are still inside the building, ya’ know?

Outdoor and greenhouse growers have another advantage because they can create habitat that naturally attracts and supports beneficial insects. Flowering companion plants such as dill, fennel, cilantro, marigolds, and nasturtiums can provide nectar, pollen, shelter, and other resources that give the good bugs a reason to stick around.

Now, companion planting attracts some fairly enthusiastic claims online, so let’s keep expectations reasonable. Putting a marigold next to your cannabis plant does not suddenly create an invisible anti-pest force field. Companion plants provide habitat, and that’s useful enough without pretending they’re magic. If you want beneficial insects living around your plants, giving them food and shelter makes considerably more sense than releasing them into an ecological parking lot and hoping they develop an emotional attachment to your cannabis.

No-till cultivation also fits naturally into this conversation because the entire philosophy involves disturbing the soil less.

Instead of repeatedly turning over the growing medium, growers allow much of the soil structure to remain intact. This can help preserve soil organisms, organic matter, fungal networks, and the larger biological community developing around the root zone.

Does that mean everyone needs to immediately convert their grow to no-till? Of course not.

Different cultivation systems have different requirements, but there is a useful principle behind it: if you’ve spent time building a functioning biological system, don’t constantly destroy it unless you have a reason.

For the right grower and the right pest problem, absolutely. One obvious advantage is reducing your dependence on pesticides. Instead of repeatedly applying something that kills pests on contact, you’re introducing organisms that actively hunt them.

Under suitable conditions, some beneficial organisms can remain active or reproduce, creating continuing pressure against pest populations, but I think there’s another advantage that’s more important than people realize.

Beneficial insects force you to become a better grower, and not just for cannbis – as someone who grows herbs, understanding this knowledge helps us alot. You stop thinking about pest management as simply:

“Bug. Spray. Bug gone.”

Yeah, don’t kill it if you don’t need to. Instead, you start asking what pest you’re actually dealing with, why it appeared, what conditions are helping it reproduce, which predator feeds on it, whether the predator is surviving, and whether pest populations are actually declining. That’s a much better way to approach cultivation, food growth, etc.

Beneficial insects aren’t magic, and they aren’t going to compensate for a dirty grow, terrible environmental control, or an infestation you’ve ignored for six weeks.

They’re tools. Really interesting, occasionally terrifying little tools.

Ladybugs can help control aphids. Predatory mites can hunt spider mites and other microscopic pests. Lacewing larvae will happily terrorize an assortment of soft-bodied insects. Beneficial nematodes, rove beetles, and parasitic wasps can fill other roles depending on what you’re fighting; but the real lesson isn’t that you should buy more bug: 

It’s that good pest management requires paying attention.

Know what’s living in your garden/at your grow. Understand whether it’s actually causing damage, and identify the pest before treating it. Fix environmental conditions contributing to the problem. Introduce the right biological control when it makes sense, and then watch what happens.

And perhaps most importantly, stop assuming every bug you find on a plant deserves immediate execution. Sometimes the weird little bastard crawling across your leaf is actually working for you.

The funny thing about growing cannabis is that eventually it teaches you to stop trying to control absolutely everything. Sometimes the thing crawling around your garden or grow isn’t a problem that needs fixing – sometimes it’s eating the problem for you.

So before you reach for the spray bottle the next time you see something moving under a leaf, take a closer look. Learn what you’re dealing with, figure out whether it’s friend or foe, and act accordingly. Your plants don’t need a sterile battlefield. They need a healthy environment where the good guys are allowed to do some of the work.

And if you do decide to unleash an army of ladybugs in your grow room, maybe don’t get too attached. Those little bastards have wings.

Until next time, keep growing, keep learning, and whatever quirky thing kids say now to sign off.