Cannabis Pest Control for a home-grower

There is so much information out there and so much garbage. Want to hear from a pro? I work directly on cannabis pest control with some of North America’s largest cannabis producers and indirectly with almost all of them. I attend garden clubs, I’m a hobby farmer and I even grow my own Cannabis. I’ll skip most of the information and give you the straight goods here: Methods that have been employed for decades.

Step one: Protect your clones.
They are dirty (covered in pests), despite what the grower will tell you. Treat them as such. Quarantine them (grow them elsewhere) for a while instead of putting them amongst more mature plants.
You could also “dip” you clones to remove some of the microscopic pests that will plague you later. Vineland Research came up with dip procedures for other crops. It can be used with cannabis and is explained here.

Step two: Protect your Roots.
If growing in a potting media, apply Gaeolaelaps gillespiei (Geo), a predatory soil-mite at the low rate of 25 mites per pot and only once. These mites will survive in your pots permanently until a chemical is drenched. They’ll control all root pests, but primarily fungus gnats and pupating thrips.
If growing in rock wool, apply the Geo every few weeks.

Step Three: Prevent Spider Mites.
Spider mites will always show up. Prevent spider mites from establishing by appling Fallacis, a predatory mite that is so aggressive and hungry that it’s initial application rate is only 2 mites per square foot! We kid you not. And when spider mites aren’t there they will survive by finding other things to eat like microscopic eriophyid mites (broad mites, russet mites…etc)

Now your plants are off to the best start they can have. From here on it’s about monitoring plant health and pest populations. If pests show up, use the reaction methods below:


Yes, you can prevent them from establishing, but most growers start their aphid control program during aphid season. Prevention can be done by releasing 250 Aphidoletes (predatory midge) every 2-3 weeks per room (up to a hectare).
If you find aphids, up this rate to 1,000 every week.

Not common, but easily controlled with 100 Encarsia (parasitic wasp) released every two weeks. Usually only needed in August.

Whitefly scale being eaten and parasitized by a few Encarsia wasps.

Thrips come in waves. In open houses they come in and leave. In a closed house they get in and stay. In either case you have to bombard them to reduce damage and prevent cycling. Fortunately with the soil mites you established early on, thrips will be controlled during pupation. However, mites on your leaves are needed to prevent thrips larva from doing damage. Apply Cucumeris at a rate of 100 per plant every week. Or apply a slow-release sachet to one of 6 large plants every week. (Every week one plant gets a new one until you’re back to the start: remove the old one and start again.)

Russet Mites / Broad Mites:
Luckily these are controlled by Cucumeris (the thrips predator). But if you don’t have thrips and need these nasty mites controlled apply Cucumeris the same way but with a much-reduced rate (about 25%).

Spider Mites:

Sometimes growing conditions favour the pest. If spider mites turn up, despite the prevention, simply release Persimilis (two-spotted spider mite eating mite) at a rate of 500 per large infected plant. Or, 100 Stethorus (spider mite eating beetle) per room up to an acre.

Above: Trials with fallacis show pale colour and spider mite damage (left), darker leaves and no more spider mite with the fallacis application (right). Remember, prevention is best.

That’s it! If this seems like a lot of info, simply do what the average grower does:

Geo in the soil.
Fallacis on the leaves.
Aphidoletes when you see aphids.

Look for a retailer or distributor of these beneficials here.

Special Considerations:

Fan Speed:
Fan speed affects all beneficials – even mites. Reduce fan speed or turn them off to give predators the advantage. Aphidoletes require fans OFF during release so they are not killed and so they can smell the direction of honeydew to find the aphids. Successful professionals manage mildew by maintaining static humidity at the plants preferred humidity of 70%, not by keeping plants artificially dry with fans. In fact, dry conditions make it worse, since a watering will spike the humidity CAUSING mildews to spore.

Every “chemical” even blended onions and cayenne pepper negatively affect predators more than pests. With prevention predators in place, you seldom need to do anything else because other natural predators will show up. The more naturally you are growing the plant the better suited it is to fight pests off by itself.

The more fertilizer the more pests. It’s linear. Plants don’t “want” nutrients; they have to absorb it when it hits the roots. Yes, you can pump it in and watch the plants sky rocket, but the result is a plant more susceptible to pests, including the dreaded mildew. Lean out your plants. Or read: All the uncomfortable facts about fertilizer

uncovered, unfertilized outdoor cannabis is pest free and beautiful.

Soil type:
This is as much of a racket as fertilizers. Cannabis is a weed. I grew it in a mixture of clay-based native soil and pea gravel with no fertilizer or tilling and got plants over 12 feet tall. What I mean is pretty much anything will do. Store-bought soils will have fertilizers built in. If plants grow quickly then the nutrients are quick release and will runout soon. If plants grow more slowly then the nutrients are slow release and you’ll not need to apply much more. However, if you can’t grow them in the ground you do need special consideration for soil. Most important should be how well you can keep it watered and how cool you can keep the roots.

Just like we did with roses in the 1800s and pretty much every other plant along the way, we bread them for specific aesthetic traits and neglected some of the obvious. Now we’re breeding pest and pathogen resistance back into roses and we’re going to have to do the same with Cannabis. When shopping for clones, ask what mildew and pest resistance performance it has. Fortunately two of the biggest cannabis companies I work with are actively breeding mildew resistance back into their plants.

Read more – I’ve got lots:

Why your cannabis bio-control program failed.

Never Buy LadyBugs

Alternatives to LadyBugs

The Bio-control tetrahedron

Using Beneficials in a home garden

Bio-Control Strategy for Cannabis

One thought on “Cannabis Pest Control for a home-grower

Add yours

Leave a Reply

Powered by

Up ↑

%d bloggers like this: