3 Common Indoor Cultivation Cannabis Pests and How to Get Rid of Them

Oct 13, 2022 | Resources

Cannabis, like any other crop grown commercially or otherwise, carries challenges. For one, you’ll have to maintain optimal climate conditions for indoor cultivation to maximize harvest. Next, you may have to deal with a pesky enemy that can come between you and a bounty harvest; a pest infestation.

However, if these measures fail, you’ll need a more customized plan suited to the kind of pest invading your crop. This guide will highlight some of the most common pests that might invade your indoor cultivated cannabis crops, how to spot them, and possible prevention measures.

Root Aphids

Although root aphids are most common in indoor cultivation, you can also spot them in gardens and potted plants.

Root aphids usually inhabit areas near or under the growth medium to feed on the plant’s roots.  The pest takes on an oblong pear-like shape with cornicles protruding from the abdomen. Although root aphids can take on many color variations, most have a yellow, brown, or whitish tint. They also possess a sucking mouthpiece that pierces the roots, bulbs, and rhizomes to extract sugary sap found on the soft plant roots.

It may be hard to spot root aphids with the naked eye. For one, they have a miniature size of about 0.5 mm. Secondly, they take the color of their surroundings and what they feed on. 

However, you’ll see a white waxy, honeydew material they secrete on the soil around your cannabis plant.

Usually, you’ll spot ants feeding on this material. Moreover, ants can also be a sign of a root aphid infestation as they have a symbiotic relationship with the pest.  The ants carry the root aphids from plant to plant, protecting them from predators, while the root aphids secrete the honeydew for them to feed on.

Problems Caused by Root Aphids

Root aphid damage can be especially prevalent in indoor cultivation. An attack will leave the plant at risk for disease and inhibit plant growth. By piercing and gnawing at the roots, root aphids prevent the plant’s absorption of moisture and nutrients. A persistent attack will eventually lead to the death of the plant root, entirely depriving the rest of the plant of essential substances required for growth. The plants then look wilted with curled, withered, and yellow leaves. This can often be mistaken for nutrient deficiency. An infested cannabis plant will produce tiny, stunted buds and lower yields.

How to Get Rid of Root Aphids in Indoor Plants

To get rid of root aphids, you must uproot all the infested plants from the area. Getting rid of the entire plant will prevent the aphids from migrating to a different plant.

To prevent root aphid infestation in the first place, avoid importing any growing medium of unknown origin into your greenhouse. For example, most nursery plants from large commercial farms carry root aphids and their eggs. Introducing these plants can lead to a rapid infestation into your otherwise clean indoor cultivation.

If you have a hydroponic system, always inspect growing cups, tanks, and trays for any attached white root aphids.

Here are some other ways to get rid of root aphids:

  • Use beneficial nematodes. Beneficial nematodes such as heterorhabditis bacteriophage, and Steinernema carpocapsae will parasitize root aphids, greatly slowing their spread.
  • Introducing biological insecticides. Any biological insecticide containing an entomopathogenic fungus attacks various pests, including root aphids.
  • Soak in a pyrethrum concentrate. Thoroughly soak the growing medium in a pyrethrum concentration for about one minute. You can swirl the roots and the growing medium to ensure a total saturation.
  • Citric Acid Root Drench. Thoroughly soak the growing medium in diluted citric acid to the concentration listed in the products mix rates.

Spider Mites

Spider mites belong to the mite family Tetranychidae. These mites are usually tiny and difficult to detect with the naked eye.  Before spotting the mites, you’ll likely notice plant damage, such as yellow or stippled leaves. In any case, check the underside of the leaves for webbings, eggs, and mites which will appear like tiny reddish brown dots though they have an oval body and are about 1 mm in size.  You’ll notice a more delicate webbing when dealing with a severe infestation. This webbing will take on a silk texture. Usually, the leaf would have lost most of its color at this stage, so it would dry up and die away. Unfortunately, at this point, the entire plant is also weakened and can die.

Although spider mites attack both indoor and outdoor cultivations, their effects can be especially devastating for indoor cultivations. This circumstance is due to controlled indoor climates, allowing spider mites eggs to hatch and grow.

Problems Caused by Spider Mites

Spider mites pierce the leaf tissue and suck up most plant sap. Light dots will show up in the areas hit by the spider mites. As the mite continues to feed, the leaves first take a yellow tint, then dry up and eventually curl and fall off the plant.

A severe spider mite infestation can lead to the entire cannabis plant dying out or causing severe damage, affecting the flowering of the plant.

How to Get Rid of Spider Mites

One way to fortify your cannabis plants against a spider mite infestation is by adequately irrigating the plants. Water-stressed plants risk catching an infection and suffering dire damage from a pest infestation.

Also, avoid using broad-spectrum insecticides on your spider mite infestation. Using these substances can exacerbate the outbreak. Instead, opt to spray an insecticide or soap solution. However, these will only work to manage the infestation or prevent further spread of the spider mite.

To get rid of the spider mite completely, there are two effective ways:  Biological control and Chemical control.

Biological Control

Introducing a species of predator mites like Phytoseiulus persimilis can help eradicate the spider mite population. Phytoseiulus persimilis feed on all life stages of the spider mites. They can eat up to five adult spider mites or 20 eggs daily.

Chemical Control

Using a chemical control such as an acaricide can also eliminate spider mites. Usually, the effects of a spray can last for a month. Acaricides, however, do not come without risk. For one, the spider mite population may develop resistance, as has been observed previously with earlier versions of miticides.  Another challenge with using acaricides is their toxicity toward fish, so proper care should be taken after application when draining the growth medium.


Fungus Gnats

Fungus gnats look like your typical house flies, only that they’re smaller in size—measuring about 3-5 mm.  They usually appear when the top layer of the growing medium stays wet for too long after watering. Their dark-headed, transparent-bodied larvae find this moist area conducive to growth.

Problems Caused by Fungus Gnats

Fungus gnats typically feed on the nematodes and decaying matter in the soil. However, their tiny offspring, in maggots and larvae form, gnaw roots and root hairs of cannabis plants.

The damaged roots cannot correctly transport food to the leaves, causing slowed growth and sometimes death of the cannabis plant. On the other hand, adult Fungus Gnats spread diseases such as pythium, which may cause root rot.

How to Get Rid of Fungus Gnats

Fungus gnats may go away unassisted, provided you let the topsoil dry before rewatering. You can also use house fly trapping techniques like the sticky card. Be sure to place the card near the soil level, as this is where the pests are typically located.  

Try using a broad-spectrum insect killer or mixing Bacillus thuringiensis (Bt) with your spray water in case of severe infestations.


Maximize Your Yields With Efficient Pest Control

The tips above will help you grow a healthy and bountiful cannabis crop from start to finish. Remember, in case of a severe infestation. You’ll need to repeat the application of the above solutions.

Try our vertical racking system if you need other creative ways to increase your cannabis yield exponentially. It features quality space saver racks customized to your facility requirement and cultivation strategy.  That’s not all. We have a line of special equipment and systems to take your cannabis cultivation to the next level. Need any help pairing up with the best system for your farm? Contact us.