14 Common Cannabis Plant Pests
You've done everything to give your cannabis plants what they need to thrive -- proper watering, light, and nutrition. Everything seems to be going according to plan, when you start noticing random defects pop up. Maybe the leaves are turning yellow and wilting. Or perhaps you start noticing chunks of the fan leaves bitten off.
Whatever the case may be, you might have an insect infestation. However, before you go all "scorched earth" on your plants, it's important to know the kind of bugs you're dealing with.
We'll go over the various types of insects that infest marijuana plants and some measures you can apply to fix and prevent them from damaging your plant in the future.
Aphids are one of the most common pests in the insect world, so naturally, you can expect them to also be attracted to cannabis.
Their appearance can be brown, black, red, yellow, green, or white. Depending on the season, they reproduce both sexually and asexually, which is why they appear so rapidly and in such large numbers.
Aphids deprive your plants of vital nutrients by sucking the sap out of new (and sometimes old) plant growth. During this process, they secret a liquid referred to as "Honeydew", which not only attracts ants, but also creates a favorable environment for mold to flourish in.
2. Barnacles and Scale Insects
Like aphids, barnacles are another pest that leave behind a sticky honeydew residue in their presence. They like to search for the perfect spot, and once established (either on the stems or underneath the leaves), begin robbing the plant of vital nutrients.
Thankfully barnacles aren't too difficult to remove, but the earlier you do so, the better as the honeydew will start attracting ants and other unfavorables.
3. Broad Mites and Russet Mites
Broad Mites and Russet Mites are two other regular contributors to the destruction of your beloved cannabis plants. Given their almost microscopic size, by the time you spot them with the naked eye, they've most likely established a fairly large population within the hundreds or even thousands.
Broad mites will concentrate their attack in specific areas so the damage is not evenly distributed throughout your cannabis plant. They do, however, prefer targeting newer growth, as it contains less cellulose making it easier to consume. If your plant has already begun flowering, the mites will attack the flower buds rendering your crop useless.
Because of the overlap in symptoms, it is common to mistake mites for issues like pH imbalances, nutrient deficiencies, and heat stress. Some symptoms to look out for are "twisted" new growth, leaves appearing "wet", or curling at the edges of the leaves.
4. Spider Mites
Spider Mites are another common type of pest found on cannabis plants. You can recognize their presence as their bites will leave behind small speckles on the leaves. Just like Broad Mites and Russet Mites, Spider Mites are also hard to spot with the naked eye, unless they've had time to multiply. They're a bit easier to spot underneath leaves, or if you notice a webbing they leave behind.
Spider mites are one of the least-liked pests on cannabis for many reasons. They eat a lot, reproduce quickly, and just when you think you've gotten rid of them, they start reappearing. Even worse, they can quickly develop immunity to your chosen treatment method, so it's best to eliminate all of them on your first pass.
5. Caterpillars and Inchworms
Worms and caterpillars can damage your cannabis plant by eating holes in the leaves. You may notice their presence because they leave droppings that appear as small black specks.
Crickets can damage your plants by eating the leaves. Mole crickets are a particular type that tunnel underneath the plants in the soil and harm the roots. The good news is that crickets are less likely than most of the other pests on this list to harm your cannabis plants.
7. Fungus Gnats
Fungus gnats are tiny little flies that are attracted to wet soil. Their worm-like larvae will burrow into the soil and eventually crawl to the surface where they develop into a fly-form.
Sometimes they can be confused with pH imbalances or overwatering. Once you let your gnat infestation get out of hand, your plants might not recover from the damage they cause.
Thankfully, fungus gnats are one of the easier pests to remove from the plants. Since they are attracted to wetness, you can discourage them by reducing the amount you water your plants. Additionally, setting yellow sticky traps and leaving a fan blowing on the topsoil to dry the soil out can help rid your plants of this pest.
Grasshoppers (or locusts) also like to munch on cannabis plants. They will cause significant damage in large numbers by leaving holes in the leaves and even eating the stems, while destroying the branches as they go along.
Leafhoppers can appear in most colors, making them sometimes hard to recognize. You can tell that your cannabis plants have leafhoppers if you notice oddly-colored clusters on the leaves. These are the locations where the leafhoppers sucked the sap out of your leaves.
10. Leaf Miners
Leaf miners tunnel their way through the leaf tissues of your cannabis plant, eating as they go, while leaving grayish twisted lines of discoloration in their trail along with their waste droppings.
Mealybugs are yet another common pest found on cannabis plants. They are small, white, and appear hairy. Mealybugs feed on the sap of the plant, which can cause damage to the buds and leaves. They also produce honeydew, a sweet liquid that can encourage the growth of mold.
12. Slugs and Snails
Beware of snails and slugs on your cannabis plants, as these slimy pests are notorious for munching on your precious buds at night. You can identify their handiwork by the telltale holes with scalloped edges on your plant's leaves and the slime trails they leave behind.
Thrips are tiny pests that can infest a cannabis plant by feeding on the plant's leaves and stems. Thrips damage the plants by laying eggs on the leaves and stems, where they will hatch into larvae and eventually begin feeding on the plant. They leave behind distinctive silver or bronze marks on the leaves, which may look like tiny snail trails or dried spit. They are attracted to the aroma of flowering plants, so they are particularly common during the flowering stage.
Whiteflies are small, winged insects that can infest a cannabis plant by laying eggs on the plant's leaves and stems. When the eggs hatch, the whitefly larvae starts to feed on the plant's sap, which can cause damage to the plant. Whiteflies are typically attracted to plants that are stressed or undernourished, so it is important to provide your cannabis plant with the proper care and nutrients to prevent infestations. They also are known to spread quickly, and can be difficult to control once they become established on a plant, so it's important to take steps to prevent infestations before they occur.
Remove Pests with a Power Sprayer
In many cases, you can start getting rid of the pests on your cannabis plants with a power sprayer, which will physically force the bugs off of the plant.
To remove bugs from your cannabis plants using a power sprayer, follow these steps:
- Fill the sprayer distilled water and mild insecticide.
- Adjust the nozzle on the sprayer to a fine mist setting.
- Thoroughly coat the infested plants with your solution, mindfully reaching the undersides of the leaves where many pests like to hide.
- Repeat the spraying every few days until you no longer see any bugs on the plants.
Note: It's also a good idea to test the spray on a small area of the plant first, to ensure it won't cause any major damage.
Insecticides are available in a wide range of formulations, such as liquids, dusts, and sprays. It's important to carefully read and follow the instructions, as some insecticides can be harmful to plants and humans if used improperly. Various insecticidal soaps tend to work best on different types of insects, so read the label.
Be Wary of Chemicals
Many insecticides are highly toxic and can be harmful to plants and humans if used improperly, so it's important to carefully read and follow the instructions on the insecticide label, and avoid applying the product directly to the buds of your cannabis plant as you don't want to inhale any residual harmful chemicals.
Avoid Contact With the Buds
To minimize the risk of contaminating your cannabis when using insecticides, you should do your best to avoid spraying the products on the buds, as they can be harmful if ingested.
Pyrethrin is a Popular Choice
As you look at the various insecticides available, you will notice that pyrethrin-based insecticides are common. They degrade quickly and are minimally toxic to humans. They are a standard control method in vegetable gardens. The issue with pyrethrins is that they are also toxic to bees, which we want to preserve. To overcome that to some extent, make sure to use these products only if the sun has already set, as the bees should be asleep, and the pyrethrin will break down before the bees wake up.
An alternative to chemical insecticides is Spinosad, which is derived from a type of soil bacteria that is toxic to many types of insects including caterpillars, thrips, and fungus gnats.
To use Spinosad as a pest control and repellant, you can mix it with water according to the package directions and apply it to your plants using a spray bottle. It's important to reapply the Spinosad regularly, as it will lose its effectiveness over time (typically within 24 hours). Additionally, you should avoid applying Spinosad directly to the buds of your cannabis plants, as it can be harmful if ingested.
Using Neem Oil
Neem oil is a type of vegetable oil that can be used as a repellant on your cannabis plants when you apply it to the leaves and stems. The active ingredients in it (azadirachtin and salannin) are toxic to many types of pests and will kill or repel them when they come into contact with the oil. Additionally, neem oil can interfere with the pests' reproductive and growth cycles, making it difficult for them to reproduce and survive.
You can mix it with water and apply it to your plants using a spray bottle. It is important to reapply the neem oil regularly, as it will lose its effectiveness over time.
One important thing to keep in mind is that you don't want to get neem oil anywhere near your buds, as it will leave an unpleasant smell and taste upon harvest.
Alcohol can be used to control pests on a plant in several ways. One method is to mix alcohol with water and use it as a spray to kill or repel pests. The alcohol will damage the pests' bodies and disrupt their cellular functions, which can kill them or cause them to flee.
Another method is to use alcohol as a bait to lure pests into a trap. For example, you can place a small amount of alcohol in a shallow dish and place it near your plants. The pests will be attracted to the alcohol and will fall into the dish, where they will be unable to escape. Alcohol can be effective at controlling certain types of pests, but it may not work for all types of pests and should be used with caution. It is important to avoid using too much alcohol, as it can also damage your plants.
Using Diatomaceous Earth
Diatomaceous earth can be used to control pests on a plant by applying it to the soil or other areas where pests are likely to be present. The fine, powdery particles in diatomaceous earth are harmless to plants and mammals, but will cause severe dehydration and harm to many types of pests. When pests come into contact with diatomaceous earth, the particles will stick to their bodies and cause them to dehydrate and die.
Diatomaceous earth can be effective at controlling and preventing pests, but is not as useful for removing an existing infestation. To use diatomaceous earth for pest control, you can sprinkle it around the base of your plants or in areas where pests are known to be present. It's important to reapply the diatomaceous earth regularly, as it will lose its effectiveness over time.
Controlling Pests with Traps
Traps can be used to control pests on a cannabis plant by attracting and capturing the pests before they have a chance to damage your plants. There are several types of traps that can be used for pest control, including sticky traps, bait traps, and pheromone traps.
- Sticky traps are coated with a sticky substance that will trap and hold any pests that come into contact with it.
- Bait traps use food or other attractants to lure pests into a trap, where they will be unable to escape.
- Pheromone traps use synthetic pheromones to attract pests, which can then be captured and removed from your plants.
You can place traps near your plants where pests are known to be present. It's important to regularly check the traps and dispose of any pests that have been caught. Additionally, you should avoid using traps that could also capture beneficial insects, as these can help control pests on your plants.
Applying Floating Row Covers
One way to control pests on your cannabis plants is to use floating row covers. These are not suitable for all grows, but they can be an affordable and effective solution. Floating row covers will physically block most types of pests, particularly larger ones, from reaching your plants. At the same time, the covers are thin enough to allow light to reach your plants and still absorb water.
Consider Beneficial Insects
Using beneficial insects can be an effective way to control pests on your cannabis plants. Ladybugs and lacewings, for example, can feed on scales and other pests damage your plants. Additionally, implementing preventative measures such as proper sanitation and regularly inspecting your plants can help reduce the risk of pest infestations.
Removing Damaged Plants or Infested Parts
If your cannabis plants have already been infested by pests, you may need to remove the affected plants or parts of the plants. This is often necessary when dealing with pests such as broad mites or leaf miners, as they can cause significant damage that the plant may not be able to recover from.
Many types of pests can affect your cannabis plants. To ensure your plants thrive, you need to take preventative actions to control the pests. You also need to watch out for them, so you can control an infestation while it is still in the early stages. There are numerous control methods available, but use caution with chemicals due to the potential for some residue to remain on the plant.