Humans have long used beneficial insects to protect their crops from pests, with historical documents suggesting that it could have been as early as 200 AD. In the Talmud, there is a mention of the use of ant colonies for control purposes. It is also known that predatory ants were used by citrus farmers in China and date farmers in Yemen to protect their crops. While in the recent past the practice has somewhat fallen by the wayside as farmers increasingly became reliant on pesticides, it is enjoying a resurgence now that there is greater emphasis on organic farming practices.
When growing marijuana, it is difficult to use pesticides since almost all kinds will affect the smell and flavor of the buds, even biological or natural ones. In most cases these chemicals will stay in the flowers even after flushing and extraction and make your marijuana unfit for consumption. This is why most expert growers will recommend pest control methods like beneficial insects before resorting to pesticides.
What are beneficial insects?
Simply put, these are insects that kill or deter cannabis pests without harming the plant itself. Beneficial insects can either act as predators or parasites to these pests; some can kill a wide variety of pests, some only a certain kind. These insects also have other unintended benefits; they can also act as pollinators so using them can balance the ecosystem of your growing setup in favor of your plants.
There are, in fact, quite a number of predators that can help you rid your marijuana of pests. This can include bats and nematodes, but for this discussion, we will only focus on insects.
Using beneficial insects on marijuana
In an outdoor growing setup, you’d rarely want to grow your marijuana without some kind of barrier like insect netting to protect it. However, this will also keep any beneficial insects out as well. In an indoor setup, the chances of a good bug crawling into your grow would even be lower. While there are products like PredaLure that are designed to attract beneficial insects, typically you will need to introduce a good amount asap when dealing with an infestation on your marijuana plant to address the problem. Fortunately, you don’t have to hunt for these beneficial insects yourself, you can simply buy them at gardening supply stores or online.
One thing to keep in mind is that the use of beneficial insects is just a part of an organic pest prevention strategy. In Common Marijuana Insects and Pests to Look Out For, we mentioned a few other components of such a strategy like companion plants that enrich the soil and also attract beneficial insects. Pesticides, on the other hand, are typically only used once beneficial insects prove to be ineffective since it can kill all of the insects in your grow area. In fact, the use of pesticides in a separate grow area can even kill insects in another.
Most popular beneficial insects for marijuana
Truth is, there’s a wide variety of insects that can kill marijuana pests and improve the ecosystem of your grow area as a whole. But for the purposes of home growing, we will narrow down our list to include only those that are the most effective and easiest to obtain.
- Effective against: Spider mites, aphids, whiteflies, Colorado potato beetles, weevils, adelgids
- Pros: Cheap and voracious feeder
- Cons: Might fly all over your grow area
- Average price: $21.99/1500 adult ladybugs
You may be surprised to know that the cute little ladybug is actually one of the most voracious beneficial insects that you can use for marijuana pest control. Even during its larval stage, Hippodamia convergens can eat around 40 aphids an hour and 60 or more in adulthood.
It is best to release ladybugs in a moist environment after sundown since they come in dry containers and they do not fly in the dark.
- Effective against: Caterpillars, aphids, mealybugs, whiteflies, scale insects, thrips, spider mites, leafhoppers
- Pros: Eats most cannabis insect pests.
- Cons: Can cannibalize one another. Cannot be released under hot conditions.
- Average price: $44/100 adults, $
The larvae of the Chrysoperla rufilabris are the ones that have a big appetite for aphids and mealybugs, but will also eat whiteflies and scale insects.
When releasing them, don’t place the larva or eggs on the ground as ants may eat them. Green lacewings may also bite you, but it is not harmful.
- Effective against: all other insects in your grow area
- Pros: Can eat all other insect pests.
- Cons: Cannot be used with any other beneficial insect.
- Average price: $10.45/2 egg cases with 50 to 200 baby mantises
The Stagmomantis is a top predator which will eat practically any insect its size, smaller, and even those that are a bit bigger. In fact, praying mantises are known to take on even small birds, and unfortunately, they will also attack their own kind if there is a lack of prey.
- Effective against: Caterpillars, ants, aphids, maggots, wireworms, slugs, fungus gnats, shore flies, thrips, most ground-dwelling pests
- Pros: Effective feeders. Completely harmless.
- Cons: Will only typically go after soil-dwelling pests. May also crawl away once the food supply is gone.
- Average price: $3/bug
Rove beetles or Atheta coriaria and Carabid beetles will eat mites, thrips and almost all smaller insects and larvae that live underground. Another benefit of using these beetles is they also eat the seeds of invasive weeds.
- Effective against: Caterpillars, leafhoppers, aphids, small to medium-sized prey
- Pros: Voracious feeder
- Cons: Is known to bite, with the toxin allergic to some humans.
- Average price: $8/bug
There’s more than a hundred different species of assassin bugs but they are often identified by their long, pointy proboscis. Like the praying mantis, these insects are voracious predators that will challenge most other bugs and small animals bigger than themselves but will also attack their own kind. Some species are also known to be parasitic to mammals so be careful when using them.
- Effective against: Thrips, mites, aphids, whiteflies, scale insects, small caterpillars, and eggs of various insects
- Pros: Feeds on a variety of insects
- Cons: Is known to bite humans.
- Average price: $169.95/1000 bugs
Orius insidiosus is particularly effective in eradicating thrips and similar bugs since they proactively look for prey. Insidious flower bugs only live during summer since they need light and warmth, which means they will survive in an indoor grow setup.
- Effective against: almost all smaller insects
- Pros: Eats a wide variety of insect pests.
- Cons: Can bite humans if provoked.
- Average price: $6.95/bug
Spiders have no problem living indoors or outdoors and they will consume almost any other small or medium-sized prey, making them one of the best predators that you can use on your marijuana plants. It can be difficult to get a bunch of spiders so what you need to do is look for their egg sacs and gently relocate them near your plants.
- Effective against: Aphids, caterpillars, beetles, thrips
- Pros: Harmless and effective.
- Cons: Can be somewhat annoying as they will land on anything.
- Average price: typically not for sale due to its life cycle
You may mistake these as yellowjackets but worry not, they do not have a stinger. While adult hoverflies work mainly as pollinators, it is their larva that has a big appetite for marijuana pests like aphids, caterpillars, beetles, and thrips.
- Effective against: Caterpillars and similar leaf-eating larvae
- Pros: Effective hunters especially at a larger scale
- Cons: Each kind of parasitic wasp will be selective of the species they will attack. Can also attack other beneficial insects.
- Average price: $27.98/100,000 eggs
Parasitic wasps, particularly the Brachonid and Trichogramma kind, are effective in dealing with a wide variety of garden pests since they lay their eggs inside their prey, killing it and multiplying at the same time. So if you see a parasitized caterpillar, don’t throw it away. Just wait for the parasitic wasps to take care of it.
- Effective against: Spider mites and other destructive mites, thrips
- Pros: Effective against other mites and is not a problem for humans.
- Cons: Can only be used to combat other mites
- Average price: $9.99/500 bugs
Phytoseiulus persimilis may not have a wide spectrum of prey but it is particularly important since it will seek and destroy spider mites and other mites that are too difficult to see. Hypoaspis miles meanwhile live in your grow medium and eat the larvae of thrips and fungus gnats.
Frequently Asked Questions
A beneficial insect is one that gets rid of pests but does not harm your plants. An example would be ladybugs which consumes a variety of harmful insects including aphids, mites, whiteflies, etc.
Ladybugs are particularly effective against a wide variety of garden pests. They are also cheap and easy to attract, and completely harmless to your plant and humans.
You can buy beneficial insects from your local gardening supply store or online. You can also buy lures or plant companion plants that can help attract such insects.
Phytoseiulus persimilis may not have a wide spectrum of prey but it is particularly important since it can seek and destroy spider mites and other mites that are too difficult to see. Hypoaspis miles meanwhile live in your grow medium and eat the larvae of thrips and fungus gnats.
Parasitic wasps, particularly the Brachonid and Trichogramma kind, are effective in dealing with a wide variety of garden pests since they lay their eggs inside their prey, killing it and multiplying at the same time.
While adult hoverflies work mainly as pollinators, it is their larva that has a big appetite for marijuana pests like aphids, caterpillars, beetles, and thrips.
Spiders have no problem living indoors or outdoors and they will consume almost any other small or medium-sized prey, making them one of the best predators that you can use on your marijuana plants.
Orius insidiosus is particularly effective in eradicating thrips and similar bugs since they proactively look for prey.
There are a lot of different kinds of assassin bugs and all are voracious predators that will challenge most other bugs and even small animals bigger than themselves.
Rove beetles or Atheta coriaria and Carabid beetles will eat mites, thrips and almost all smaller insects and pests that live underground. They will also eat seeds of invasive weed species.
The Stagmomantis is a top predator which will eat practically any insect its size, smaller, and even those that are a bit bigger.
The ladybug (Coccinellidae) is actually one of the most voracious beneficial insects that you can use for marijuana pest control.
Beneficial insects serve to bridge between prevention and treatment since you can use them to deal with pests that are able to bypass your preventive measures. However, you have to be able to identify the exact pest that you will be dealing with and in turn, use the right beneficial insect to counter them for the treatment to be effective. You also need to know the right time to release them; some beneficial insects have to be released earlier before a pest invades so that they won’t be overrun while some need to be deployed when there are already pests waiting to be consumed. This seems like a lot to learn but the reward for knowing how to use beneficial insects effectively is great; it will allow you to grow fully organic marijuana free of any chemical residues.