Common Cannabis Pests and How to Mind Them
by Luis Rivera, Advanced LED Lights
Like any crop, cannabis can often find itself at the mercy of ravenous animals, desperate for a field feast. So, whether you’re growing indoors or outdoors, knowing your plant’s enemies is the first step in protecting them. From crickets to caterpillars, moles to mites, this article outlines cannabis’ top predators, their tell-tale signs, and how to best remove them.
Ants on cannabis plants can be bad news. These well-known insects damage the root system, negatively affecting the overall plant yield. Even worse, an ant invasion usually precedes an aphid infestation.
While aphids feed on the cannabis leaves, ants often harvest the plant’s honeydew for nutrients. Therefore, ants would always protect the aphids, allowing the pest colony to multiply.
Cinnamon is known to be a famous ant treatment for people with small gardens. It works as a repellent and an exterminator since the insects are repulsed and killed by it. Growers should sprinkle or water it onto the soil where they are nesting. In general, however, there aren’t a lot of treatment measurements that can completely get rid of ants. Gardeners can encourage their natural predators such as frogs and slow worms to come to your garden. Finally, growers can grease your trees and stems of plants, or place them in a moat of water. Ants won’t be able to cross the water and the greased parts.
Birds are an outdoor cannabis pest, who might help you out by eating insects or just ruin your future harvest by stealing seeds.
Birds are definitely easier pests to spot. You need to check on your crops regularly if there have been any bird-plant interactions or seeds disappearing.
A classic solution is to distract the bird pests by placing scarecrows or shiny objects (e.g. cans) near your crop. Another distraction is a bird feeder situated nearby. Alternatively, use a lightweight net or PVC cover to create a barrier.
Crickets and grasshoppers
These noisy insects are common cannabis pests that live among the branches and fee intensively on leaves.
Crickets and grasshoppers are outdoor cannabis pests that can be identified by the sounds they make and their noticeable bite marks on the plant leaves.
Pest controls, like spinosad products, can attack the cannabis pest directly and kill them. Additionally, treatments with neem oil, insecticidal soaps, and pyrethrin-based products are also suggested when dealing with grasshopper and cricket invasion on cannabis plants.
Gophers and moles
If growing cannabis in North America, these toothy rodents can be an exhausting underground menace.
Rodents are the nightmare of every outdoor horticulture farmer because they are hard to identify unless they are spotted in action or their traces and earth holes are noticed.
To deal with gophers and moles, try spraying castor oil and garlic water mixture over the garden soil, which should make the pests migrate. Alternative organic pest control solutions are using hardware cloth, setting traps, or even simply getting a cat.
Just like the name implies, leaf miners dig tunnels into plants’ leaves where they can feed and lay eggs.
After inflicting their initial damage on the plants, the leaf miner larvae eat the tissue and leaves, leaving long brown traces on the cannabis leaves. Those brown lines are the warning sign you need to look for in order to identify the unwelcome pest in time.
Luckily, the adult leaf miners can be stopped from laying more eggs. A savvy grower should place adhesive strips near the crops. But to deal with the larvae, one can either manually remove the pest or treat the plant with insecticides such as spinosad, a natural substance made by a soil bacterium that can be toxic to insects.
Red spider mites
Red spider mites damage the cannabis plant by sucking the sap from its leaves, killing the crop in a tight timeframe.
To notice traces of red spider mites on cannabis plants, you need to look for white spots on leaves. There might also be yellow or black spots on both sides. However, these symptoms can be confused with a lack of nutrients. To be sure of the cause, it’s advisable to use a magnifying glass.
Red spider mites thrive in dry areas and multiply in high temperatures. So a proper mite-free growing environment would be a well-ventilated space with a humidity of 55-60 percent and an average temperature below 25 degrees Celsius. Once spotted, the damaged leaves need to be treated by spraying a mixture of alcohol and water on the problematic areas. Other products that could help are potassium soap, neem oil, and ecotenona.
Caterpillars are cannabis pests who need to vegetate in order to form their chrysalis, so they feed on plants at a fast rate.
Yellow or translucent eggs, small teeth marks, and black droppings on the leaf surface are all major signs which should alarm any grower for caterpillar invasion.
Luckily, caterpillars on cannabis plants can easily be spotted and removed by hand. Alternative treatments include applying pepper and garlic insecticide, as well as introducing Trichogramma wasps or spined soldier bugs to the plantation.
A fast, tiny insect, thrips can be hard to spot and treat.
Sticky strips could be used to identify the thrips’ invasion, but another way to determine their presence is to look for brittle leaves and silver markings on a plant’s surface.
Spraying with potassium soap or neem oil could be extremely helpful, unless the flowering process has already started. If this is the case, then alternative cannabis pest control measures need to be taken into consideration – including wasps or insidious flower bugs.
Whiteflies are a common pest that weakens cannabis plants by sucking the sap from their leaves.
The obvious evidence of whitefly infestation on cannabis leaves is the presence of tiny flies every time the plants are shaken. Other symptoms of invasion include yellowed leaves with white powder on their underside.
The stubborn whiteflies are tough to get rid of. They need to be treated persistently with various methods like planting repellent crops (e.g. basil), strategically placing yellow sticky strips, or spraying with neem oil or potassium soap.
Aphids are extremely fast at spreading and reproducing. Like other cannabis insect pests, they feed on the leaf sap.
If you notice dry yellowish leaves, honeydew and colonies under stems and leaves, then you are probably dealing with an aphid invasion.
The aphid cannabis plant pests can be crushed or removed manually, and decaying cannabis leaves need to be removed. Introducing plant-friendly insects to feed on aphids is also a solution (e.g. lacewing larvae, parasitic wasps, ladybugs).
Another nemesis of marijuana growers, cochineals reproduce at a rapid rate and their droppings decay plant material and lead to cannabis leaf problems.
These common cannabis pests are white or brown in color with a white fluff cover. Tiny and hard to detect, they initially appear on the stems and then infest the whole cannabis plant.
Even though cochineals are resistant to some insecticides, removing them by treating the leaves with a mixture of alcohol and water (50/50) would be useful to eradicate this pest. All severely affected parts of the plant should be removed.
Roundworms (nematodes) have 25,000 registered species, half of which are plant damaging parasites, while the other half are actually beneficial for the cannabis crop.
Symptoms of nematodes on a cannabis plant include chlorotic leaves, lack of vigor, slowed growth, and wilt.
The treatment against nematodes on cannabis plants is applying products like Trichonema Prot-L, neem oil, skunk neem, and laotta. You can also ensure roundworm-free plantations by regularly changing the substrate.
Slugs and snails
Snails and slugs are common pest of any crop, cannabis included.
Spotting them is relatively easy since they leave shiny trails of transparent mucus.
The best cannabis pest control options for slug and snails is removing them manually at night when they are most active. Alternative treatments include building a barrier around the crop, placing baits and lures (e.g. mix of jam and beer), and using the predatory slug Ruminia decollate.
Broad mites (Polyphagotarsonemus latus) are a species of miniscule mites, too small to see with the naked eye, that damage many crops.
Typical symptoms mimic herbicide damage. Leaves turn small, stunted, and they sometimes curl downward and inward.
The pests can be controlled via applications of selected miticides labeled for broad mites. Many miticides that work on other mites, such as spider mites, make little impact on reducing these pests.
Cannabis pests’ identification and extermination is crucial. It is essential for any grower to be able to identify a pest and react fast to protect their greenery and ensure the well-being of their plantation.
Update: This article was updated on August 13, 2021, to include information on broad mites.