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ABCs of removing insect pests

Pest Guide: Insects

No gardener likes the thought of heading outside to check on his or her plants only to find a full-blown insect infestation. For marijuana growers, insects can be more than just a nuisance. They can destroy crops, and for commercial growers, threaten livelihoods.

Don’t start panic buying insecticides yet, though. Before resorting to chemical warfare, which often does more harm than good, growers should take a moment to familiarize themselves with natural and less ecologically harmful alternatives.

Aphid Midges

Aphid midges are beneficial insects that prey on aphids. They look like tiny mosquitoes, but they’re actually flies in the Aphidoletes aphidimyza family. Growers can purchase them from most beneficial organism suppliers, then simply apply them to the soil surrounding the affected sativa cannabis or indica plants.

Bacillus Thuringiensis

Bacillus thuringiensis (B.T.) is a soil-dwelling bacterium that feeds on leaf-eating insects such as caterpillars and fungus gnats. When susceptible insects ingest these parasitic bacteria, it reacts to the cells in their stomachs and renders them unable to eat. Different strains of B.T. target different pests, so read the label to make sure it will work.

Beauveria Bassiana

This naturally occurring soil fungus causes white muscardine disease in aphids, termites, thrips, whiteflies, and some species of beetles. It’s a parasite that germinates its spores inside of its prey, killing them as it grows. Beauveria bassiana can also control caterpillars, mites, stem borers, and even fire ants, but does not affect people or animals.

Boric Acid

Boric acid has a history of use in combating ants, termites, and cockroaches dating back to the 1930s. Growers can buy it at almost any hardware store or grocery store and apply it in a powdered form in affected areas, but it needs to be reapplied after each rain.

Those looking for a longer-acting solution can mix it at a ratio of one teaspoon boric acid to six tablespoons of sugar, dilute it in two cups of water, and use it as an insect bait. Create a trap by drilling some holes in a plastic container, soak some cotton balls in the solution, and drop them in. Place these containers throughout the garden and replenish the solution weekly until the pests are gone.

Bug Traps

Traps aren’t usually designed to kill bugs, but they’re useful for trapping them. i49 growers can then dispose of the insects themselves and keep track of how severe the infestation is by noting how many bugs are in the traps each day. Crickets, fungus gnats, snails, and slugs can all be baited and trapped. Use yellow sticky cards for fungus gnats, cricket bait and traps for crickets, and a shallow container filled with a mixture of flour and beer to trap slugs and snails.

Capsaicin (Hot Peppers)

Capsaicin is a naturally occurring chemical produced by spicy peppers to protect their seeds from insects and critters. It’s great for repelling aphids, whiteflies, spider mites, and thrips. Growers can companion plant hot peppers around their garden, make homemade pepper sprays using two tablespoons of ground red pepper per gallon of water, or buy commercial products at a garden center. Mix the watered-down capsaicin with six drops of Castile soap to help it stick, then apply the mixture as a foliar spray to any affected plants.

Carbon Dioxide

Indoor growers and greenhouse growers may not deal with as many insect infestations as those who plant their marijuana straight into the ground, but they’re not immune to them. One great way to kill aphids, spider mites, thrips, and whiteflies is to supplement carbon dioxide in the grow room to around 10,000 ppm. As an added bonus, growers who supplement carbon dioxide also report heavier yields.

Diatomaceous Earth

Diatomaceous earth contains sharp, ground-up seashells. When small insects like ants, fungus gnats, or thrips eat it, the sharp fragments cut them open and kill them slowly. In the case of ants, this means the insects have enough time to bring the diatomaceous earth back to the colony, helping to spread it among the entire population. Diatomaceous earth can also be used against slugs and snails, and it can be purchased in just about any garden center. Simply sprinkle a row of this dry white powder in a protective circle around each 3 kings or strawberry cough marijuana plant so that crawling bugs cannot access the stem or roots.

Floating Row Covers

Floating row covers create a physical barrier against caterpillars, crickets, leafhoppers, leaf miners, snails, and slugs. They’re made out of netting and can be draped directly over the plants or installed on frames. Floating row covers are really only effective at protecting young plants, though. As the plants get larger, it becomes difficult to preclude all pests effectively.


Lacewings are predatory insects that look like tiny green flies. They’re best known for attacking aphids but will eat mites and other soft-bodied insects like thrips, mealybugs, young whiteflies, and even small caterpillars. One green lacewing larvae can eat 200 small bugs per day, so these insects are best left in the garden.


Ladybugs aren’t quite as prolific of feeders as lacewings, but they can eat up to 60 aphids per day. They also prey on scales, mealybugs, mites, leafhoppers, and other soft-bodied insects. Most outdoor growers already have at least a few ladybugs in their gardens, but those who don’t can purchase them online and introduce them as a form of pest control in your indoor cannabis or outdoor seed garden.

Minute Pirate Bugs

Minute pirate bugs are beneficial insects that pierce their prey with their tiny beaks and suck them dry. They feed on aphids, mealybugs, scales, spider mites, thrips, and some small varieties of caterpillars. Once they’ve consumed all the pests in the garden, they can also feed on pollen and plant juices, which means most growers only need to introduce minute pirate bugs into their gardens once to reap the benefits for the rest of the season.

Neem Oil

Neem oil is a natural insecticide that also kills many types of mold and fungus. It can be used on just about any type of insect pests, including aphids, broad mites, fungus gnats, leaf miners, mealybugs, scales, thrips, and whiteflies, among others. Apply neem oil as a mist directly to the plants in the early morning or before the sun goes down.

Parasitoid Wasps

Parasitoid wasps don’t sting people, so don’t be put off by the name. They feed on arthropods and lay their eggs in pest insect larvae, eggs, and adults. The wasp larvae then eat the insects from the inside, killing the hosts.

Predatory Mites

Most mites are bad news for marijuana growers, but predatory mites are the exception. They feed on fungus gnats, spider mites, and thrips and are known for breeding rapidly indoors, making them a great option for indoor or greenhouse growers. When ordering predatory mites, purchase around one hundred of them for every 25 sq ft of grow space or marijuana garden.

Predatory Nematodes

These nematodes live in soil, where they eat the larvae of pests that lay their eggs nearby, including fungus gnats and thrips. Some species of nematode also prey on insects like beetles, borers, crickets, cutworms, mealworms, flies, mosquitoes, and others. Each species targets a different kind of pest, so make sure to buy the right one.


Pyrethrum is a flower in the chrysanthemum family used to produce insecticides. It can control aphids, ants, beetles, caterpillars, cabbage worms, flea beetles, fungus gnats, leaf miners, mealybugs, potato beetles, scales, spider mites, and thrips. Growers should note, however, that while pyrethrum doesn’t pose a serious health threat to humans or mammals, it is toxic to fish and many beneficial insects. It makes little sense to apply pyrethrum in conjunction with natural control mechanisms like lacewings and ladybugs, for example, since it will kill them along with the pest insects.

Rubbing Alcohol Mixtures

Banana kush weed or candy cream strain growers can use a mixture of alcohol and water to kill many types of bugs. Use a ratio of 9:1 water to rubbing alcohol and apply it directly to the bugs. Alcohol begins to evaporate as soon as it comes into contact with the air, so it will only work on those bugs that come into contact with the mixture. It’s most effective as a treatment for mealybugs and spider mites.

Saccharapolyspora Spinosa

Saccharapolyspora spinosa is a species of soil bacteria discovered in 1975 and registered as a pesticide in 1997. It is sometimes used to treat fleas thanks to its low toxicity levels for humans and pests, but it is very effective at killing aphids, borers, caterpillars, fruit flies, leaf miners, spider mites, and thrips. Look for it under the commercial name Spinosad.


Insecticidal soaps can be sprayed directly onto marijuana plants such as ak47 marijuana to control aphids, mealybugs, scales, spider mites, thrips, and whiteflies. Just add two tablespoons of Castile soap to one quart of water to make a homemade version that will work just as well as commercially available insecticidal soaps.

The Bottom Line

Controlling pests in an indoor grow room or outdoor garden doesn’t have to involve dangerous chemical insecticides, which kill beneficial predatory insects and wasps as well as target species. Growers should now have a decent idea of what less-lethal and organic options they have at their disposal, as well, and should choose the ones that best suit their needs.