August, 03
by RT

Cannabis Pests Prevention

Cannabis is a huge hit (no pun intended) and not just among people. Deer, birds, moles, squirrels, and raccoons are just a few animal fans that cause issues for outdoor growing areas while smaller admirers present problems for both outdoor and indoor growing environments.

Cannabis Pests Prevention

One of the main benefits of growing indoors is the prevention of insects and infestations. However, if growers don't keep the environment clean and/or aren't cautious about what they're tracking in, these tiny admirers can wreak havoc and destroy an entire harvest.The first step to avoiding insect infestation, as well as, fungus, mold, mildew, etc., is to ensure your grow room is kept extremely clean and that proper grow room air filtration is implemented to control and remove contaminants.

Find out how to identify insect pests and the best ways to prevent them below (detailed prevention instructions can be found at the bottom of the article).

Aphids - One of the most common cannabis pests 

  • They are oval-shaped and may or may not have wings.
  • Colors range between grey, white, green, yellow, black, brown, or red based on their stage of life and where you're located.
  • They will feast on any part of a plant by biting into the leaf, stem, or bud to feed on the juices inside.
  • They generally live in colonies of tens or hundreds and hang out on the undersides of stems and leaves.
  • Once attached, an aphid becomes fixed and is easy to spot.
  • Females do not require copulating to reproduce and will produce offspring between 3 to 100 times a day.
  • Another issue caused by aphids is honeydew, sugary liquid water that they secrete in large volumes. Honeydew drops attract sooty mold that can grow on honeydew deposits found on leaves and branches turning them black.
  • If you notice ants around the base of your plant, this is also a sign of an aphid infestation as the ants are attracted to the sweet honeydew and protect aphids from predators.

Aphid Prevention

  • If a plant is infested move it to an outside area where you can spray it to cut down the population,
  • Remove leaves and buds that are heavily infected
  • Insecticidal soaps
  • Neem oil
  • Spinosad
  • Essentria IC3


  • Barnacles are scale insects and can appear in different colors and patterns.
  • Scale insects may vary in appearance but act the same.
  • They can seem like growths on a plant or look like bugs. 
  • They hang out on stems and under leaves.
  • Once they're established barnacles become stationary and suck the life out of the stem and leaves of plants.
  • If infestations get too bad, your plant will start to weaken.
  • Similar to aphids, barnacles also release honeydew. 

Barnacle Prevention

  • Use a small one-hand pressure sprayer to spray off the bugs.
  • Insecticidal soaps
  • Neem oil
  • Spinosad
  • Essentria IC3

Broad Mites

  • Broad mites are very small and difficult to see even under a microscope.
  • When your plant is infested with broad mites or russet mites new growth may come in twisted, blistered, and appear wet or plastic-like.
  • If your plant is in the flowering stage, buds may turn brown and die.
  • Broad mites normally hang out inside the crevices of leaves inside buds and they lay eggs inside of the plant.
  • Infestations are commonly diagnosed as overwatering, heat damage, or a nutrient deficiency.
  • Prevention is different for broad mites since they are one of the toughest to get rid of.
  • When dealing with broad mites, it's recommended that you treat your plants for at least a few weeks at several times a week or even daily.
  • Repeat treatments for five more weeks after the mites are gone. Since they lay eggs inside of the plant they can come back if not completely destroyed.

Broad/Russet Mite Prevention

  • Neem oil
  • Essentria IC3
  • Insecticidal soaps
  • Might Wash
  • Avid
  • Forbid
  • Diatomaceous Earth
  • Heat

Caterpillars, Inchworms, and Loopers 

  • Caterpillars have a lot of legs and are a variety of colors.
  • Loopers have two sets of feet, one at that back and one at the front. They arch their back to pull the rear feet forward.
  • Inchworms have three pairs of front legs and either two or three pairs of rear legs. These worms can be found in any color and are any size about half an inch.
  • All three will eat through leaves, buds, stalks, and the main stem.
  • They defecate often with fungus and rot quickly following.
  • They are not as common for indoor grow rooms and if proper air circulation is in place they should not be an issue.
  • If you notice holes in your leaves and think that these worms are in your plants, spray pyrethrum and shake your plant to make them fall out. 

Caterpillar, Inchworm, and Looper Prevention

  • BT spray
  • Spinosad 

Fungus Gnats

  • Fungus gnat larvae are hard to see with the human eye and have transparent bodies and black heads. They infest the upper roots of plants. They enjoy dark and moist environments and can be found at the base of your plant.
  • Adults are grey to black in color and are very small with long legs. The females lay around 200 eggs per week within the first few inches of moist soil and larva can be typically be found in water runoff.
  • Adult fungus gnats will generally be found swarming around the lower portion and at the base of your plant along with the larva.
  • Once infested in the root system, these insects damage larger roots resulting in weak plants, slow growth, and fading foliage.
  • Fungus gnats stick to the sticky flowering green and are almost impossible to remove.
  • The damage from these pests makes cannabis plants very vulnerable to various types of fungus.

Fungus Gnat Prevention

  • These gnats are common for plants that are watered too often.
  • Allowing the top inch of soil to dry out before watering can make them go away on their own.
  • Blow air over the soil to dry it out making it harder for them to fly around and reproduce.
  • Treat the top layer of soil with Neem oil.
  • Apply Diatomaceous Earth to the top of the soil and around edges.
  • Yellow sticky traps placed on the floor near plants and hanging near the top will help discourage their attack indoors.
  • If you have a bad infestation, it may take weeks of good watering practices before they're gone.

Leaf Miner

  • Leaf miners are the larva of any bugs that live inside leaves and tunnel through them to eat.
  • They are normally around 1/8" thick when hatching.
  • It is uncommon to notice leaf miners before noticing the damage they leave.
  • These pests live inside the tissue of leaves, eating the best parts, and leaving a trail of damage behind.
  • If you find a leaf that a miner is burrowing through it may be visible.

Leaf Miner Prevention

  • Environmental control indoors and in greenhouses will prevent bugs from laying eggs in your plant.
  • Remove affected leaves if you can, if you don't want to remove the leave, crush the larva by pressing your fingers together where the trail is visible.
  • Spinosad
  • Neem Oil
  • BT Spray (if evidence of caterpillars or loopers is present)

Spider Mites - Very common cannabis pests that are difficult to get rid of

  • Spider mites live underneath the leaves of a plant and are so tiny they look spots to the naked eye.
  • The leaves of your plant will be covered in yellow, orange, or white speckles which may be misdiagnosed as a nutrient deficiency.
  • When spider mites attack a certain spot you will see a lot of specks near each other and the leaves may start to appear yellow or bronzed.
  • When the infestation grows you'll notice webbing that may cover foliage, flowers, and even entire buds.
  • Their sharp mouths pierce individual plant cells and suck out the liquid that keeps your plant alive.
  • Spider mites are visible under a strong magnifying glass and are commonly brown with two spots but can be yellow and white or red.
  • Female spider mites become fertilized for their entire life cycle once they mate and lay on average around 100 eggs every five days (around 1 million a month).
  • 75% of all spider mite eggs become female
  • Spider mites will quickly take over a plant and can easily develop resistance to almost any method used against them
  • It's recommended to use various methods to remove them.

Spider Mite Prevention

  • Reduce their population by controlling the heat, this makes it harder for them to reproduce in cooler temperatures.
  • Blowing constant air over the plants combined with the cooler temps creates a cool breezy space and makes it harder for reproduction.
  • Taking plants outside and spraying them off if possible to reduce population before starting the main treatments
  • Spiders may be brought in by a new plant or a clone. It's important to look for new bugs or tiny spots on leaves using a microscope or magnifying glass.
  • Keeping new plants in quarantine for at least a week and checking daily for bugs is great practice to implement.
  • Mighty Wash
  • Spinosad
  • Essentria IC3
  • Insecticidal soaps
  • Neem oil
  • Diatomaceous Earth
  • Azamax 

Thrips - Another common insect pest for indoor growers

  • Because it is difficult for thrip to reproduce in large quantities outside they make their way into indoor growing spaces.
  • They are very very small and can almost be any color.
  • They may appear dark, yellow, golden, or translucent.
  • Based on the stage of life they may or may not have wings.
  • It's hard to see a thrip on its own but they generally move in herds together.
  • They rip tiny strips off the tops of leaves and drink the juices.
  • Thrip leave behind shiny silver or bronze spots where the leaves were bitten. Damage has been described as dried spit.
  • They strip leaves of chlorophyll and the leaves turn brittle and dark and then crumble
  • Female thrip creates a hole in the plant matter where she leaves her eggs.
  • Thrip flourishes and reproduces inside of buds.
  • Shaking branches will make thrip fly and/or jump to other places to live. 

Thrip Prevention

  • Insecticidal soaps
  • Neem oil
  • Spinosad


  • Similar to spider mites, whiteflies hang out and steal nutrients from underneath cannabis leaves.
  • They are easy to spot but can become hard to get rid of if ignored.
  • Their eggs stick to the leaves like glue and cannot be wiped off.
  • They prefer weak plants and attack them from the top down.
  • Leaf damage from whiteflies is similar to spider mites.
  • The longer damage continues the more strength and energy.

Whitefly Prevention

  • Insecticidal soaps
  • Neem oil
  • Spinosad
  • Essentria IC3

Prevention Methods

Move your plants outside and use a power sprayer to physically spray off all the bugs. You should also remove heavily infected parts of the plant and for double effectiveness use an insecticide while spraying to treat future attacks.

Avid a harsh and expensive but can work if nothing else is getting the job done. This insecticide works by infiltrating inside of the plant tissue and should not be used in the flowering stage

Don't use this product more than once or twice in a row as the mites can become resistant. If you decide to use systemic insecticides, switch back and forth between Acid and a product like Forbid.

Azamax drench foliage by spraying plants 15 minutes before the lights go out. Use a fan to help dry the plant. If you think the mites are gone you can add a little Azamax when watering to kill spider mites in the soil.

BT (Bacillus Thuringiensis) Spray - a biological insecticide that kills larva and prevents pests from being able to eat. You'll want to apply this spray as soon as you notice any signs of an insect infestation.

Diatomaceous Earth is a powder-like substance that is sprinkled on top of the soil and anywhere else in the room. Diatomaceous Earth is harmless to animals and plants but is exceptionally sharp at a microscopic level.

  • It will tear and dehydrate mites on physical contact but it will not get rid of an infestation. It will, however, prevent and slow it down when used effectively.
  • It will kill adults and larvae fungus gnats that touch it.

 Essentria IC3 Insecticide, also known as a bed bug killer, is a mix of various horticultural oils that are organic and safe for humans. This method only stays effective on the plant for about 8 hours so you'll need to apply it daily or combine with another option.

 Forbid like Avid is made with strong chemicals and is expensive. It also infiltrates the inside of plant tissue. Don't use this product more than once or twice in a row as the mites can become resistant. If you decide to use systemic insecticides, switch back and forth between Forbid and a product like Avid.

 Heat runs out broad and russet mites. Growers may try and get rid of them on small plants by submerging the plants in hot water for 10-20 minutes at 105°F or by heating up to grow room to 115°F for 60 minutes. Please keep in mind that this can be dangerous to the health of your plants.

 Insecticidal soaps weaken the outer shell of aphids, barnacles, mites, thrips, and whiteflies and are safe to use on plants. Additional applications may be required. Even though this is considered safe it's best practice to avoid getting any on buds.

 Mighty Wash can be used to drench leaves 15 minutes before lights go out ensuring that the foliage under the leaves and top of your soil is covered. Use a mister to spray and a fan to help dry.

 Neem oil is an all-natural remedy that is effective against many types of bugs and mold. However, it leaves an unpleasant smell and taste so don't let it near your buds.

 Spinosad products are organic and completely harmless to pets, children, and plants.

  • Spinosad can be used directly to kill aphids and leaf miners can be sprayed liberally.
  • May kill come barnacles but their shell makes them resistant, it’s important to cover all of the vegetation.
  • Not as effective as BT spray for caterpillars, inchworms, and loopers, but can kill them if sprayed directly on contact
  • Spinosad can be used to kill spider mites, thrips, and whiteflies on contact and can be used when water plants to kill spider mites from the roots.


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