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Cannabis Pests - Aphids

Created by
JoshuaHolt JoshuaHolt
Added 21 December 2020

Cannabis Pests - Aphids

If you've noticed sticky excrement or sooty mold on the leaves of your cannabis plants, you could have an aphid problem. Prevent the issue from getting worse by taking the time to give your plants the treatment they deserve. This article teaches you how to identify aphids and what to do to get rid of them before they take over.

What Are Aphids?

Green Vs Black Aphids

Aphids, also commonly named greenfly or blackfly, are small insects that can be found in many parts of the world and affect plants everywhere. They are mostly found outdoors during spring time, but they can also find their way into indoor grow spaces.

Aphids are not always the same colour and can be yellow, green, red, white, black or brown. The varieties that attack cannabis plants tend to be either green or black, but it depends on which part of the world you're in. They can be classified through two tubular formations on the bottom end of their bodies, called cornicles.

Aphid Life Cycle

Aphids vary in size and go through various stages in their life. The eggs hatch into nymphs, which grow into adults that have an oval-shaped body and long antennae. Some adults can also develop wings. Wings are more common once the colony is very overpopulated.

Nymph aphids (young aphids) look quite different to adults and have a thinner body that is usually translucent white or yellow. After around 7-10 days as a nymph aphid, it will shed its skin to become an adult that develops the ability to reproduce.

Cannabis plants can be severely damaged by aphids, as they feed off the sap and nutrients in the leaves, puncturing the cells with their tiny mouths. On top of that, they can also carry disease and spread viruses very easily.

The Causes of Aphids

Winged Aphids

Aphids can colonize a cannabis crop through just a single winged variety entering the garden. They can reproduce asexually, meaning aphids can give birth without a partner. They eventually grow into a full colony of mostly females reproducing at rapid rates. Some varieties can even give birth to live young and do not lay their eggs. 

The winged aphids arrive from other plants that have been over colonised, making them quite hard to avoid outdoors. Within a few weeks there can be thousands sucking the life out of a plant before they move on to the next.

Identifying Aphids

Aphids Produce Honeydew Which Can Lead To Sooty Mold

As aphids munch away at the leaves, they produce a sweet excrement known as honeydew. This waste produced by the insect creates a risk of sooty mold developing. When this happens, black, powdery mold grows over the honeydew and spreads onto the leaves, preventing the plant from photosynthesising and functioning correctly.

Identifying aphids can be tricky to spot when populations are still small. Most of the time they are green, which makes them even harder to see. If you notice a decline in plant health or suspect an aphid, look out for white/yellow eggs or nymphs underneath the leaves in groups.

Leaf Damage From Aphid Infestation

Symptoms of aphid infestation:

  • White spots on undersides of leaves (eggs)
  • Clusters of adults around stems and bud sites
  • Yellow, curling and wilting leaves
  • Slow plant growth
  • Sticky excrement (honeydew)
  • Black, sooty mold

Aphid Treatment

Heavy Infestation Of Aphids Under Cannabis Leaf

It's best to get an aphid problem under control as quickly as possible before plants get too stressed. As we know, aphids can multiply very quickly and after a while a cannabis plant cannot support their spread, so we must get them out. Here are a few ways to rid your garden on aphids.


One of the most effective ways to get rid of aphids quickly is to simply remove the affected areas. Fortunately, aphids tend to group themselves together under the leaves, meaning you can often prune off hundreds in one go without stressing your plant too much.

You can also remove plenty of aphids by hand. Use gloves and make sure you kill them to avoid them returning to your plants.


Spraying down your cannabis plants with water can do a good job of removing a large amount of aphids but it probably won't solve the problem completely. After pruning, this can be a useful way to get rid of a few more aphids before applying any stronger treatments to your plants.

Biological Control

Ladybug Eating Aphids

Introducing predatory insects into your garden is another natural way of getting the aphid populations under control. Lady bugs have a large appetite for aphids and can be bought cheaply online and at some gardening stores.

Remember, it is important that the environment is also favourable for the lady bugs, or they may just fly away. It's best not to use insecticides or any other products as it could create a reason for them to leave. An aphid problem may even attract lady bugs without your intervention.

If you grow outdoors, it helps to have a variety of plants that create an inviting ecosystem for beneficial predators to enter naturally. Wasps are also known to attack aphids so a few bright yellow or orange flowers around could be a good idea.


Foliar Spray Can Be Applied To Control Aphids

Applying a mild insecticidal soap solution causes the aphids to dehydrate, ultimately killing them. Can be quite strong for cannabis plant and other insects, so a weak-mild solution is recommended. After 2-3 days of daily application, the aphids should be more or less eradicated. Check the dilution strength on the label for further instruction.

Feel free to look into other organic insecticides such as Essentria IC3 or Spinosad, which are also widely available for purchase and work effectively to control cannabis pests without the addition of chemicals. 

Neem Oil

Neem oil is a useful product to have on your shelf for general pest control management. Although it might not kill aphids, it certainly deters them and leads them away from your garden.

To get rid of aphids using neem oil, prepare a foliar spray using neem oil, insecticidal soap and warm water. Apply it 2-3 times a week to your plants, being careful not to mist any flowers (avoid using in the last 3 weeks of flowering as flavour could be affected).

Bear in mind neem oil can be harmful for other beneficial insects so use it with caution. Preferably avoid applying neem oil when there is a presence of lady bugs or bees and use it in the morning if growing outdoors. 

Tomato Leaf Spray

Tomato Leaf Spray Can Help To Deter Aphids

The tomato plant contains alkaloids that are toxic to aphids, but are safe for humans. When the leaves of the tomato plant are broken, they release alkaloids which mix with water to create a repellant.

To make a tomato leaf spray, simply allow a handful of tomato leaves to steep in water over night and strain. Alternatively, blend the leaves with water and strain through a coffee filter. Apply 2-3 times a week, making sure to cover all sides (especially on the undersides of the leaves).

Natural Repellents

Aphids do not like acidic environments, so you can consider growing other strong smelling plants such as garlic, onions or chives, amongst others. Distribute repelling plants around the garden for preventing aphids from even being interested in the space. Don't forget the tomatoes.

Tips For Preventing Aphids

Aphid Infestation On Cannabis Flower

Aphids are one of those insects that can appear out of nowhere, even with the right management. However, there are always precautions we can take to ensure our cannabis garden is well protected.

Here are some further tips to keep your plants safe from aphids:

  • Create a stable environment and maintain temperatures between 20-25°C
  • Provide ventilation using oscillating fans
  • Regularly inspect the undersides of leaves
  • Watch out for any discolouration or slow growth
  • Add a dust/bug filter to your inline fan
  • Plant aphids repelling plants around your garden
  • Be extra cautious during spring.

HazeyBobby's G13 Haze (Barney's Farm) grow from GrowDiaries. Aphid problem started but harvested early due to powdery mildew.

Tip: Hot, humid conditions are normally the culprit for many common pest problems so make a habit of checking temperature and humidity on a daily basis.

If you have any tips regarding pest control and aphids, feel free to leave a comment for the community down in the comments section!

External References

High-Altitude Migration of Aphids In Maritime and Continental Climates. - Berry, R. E., Taylor, L. R. (1968)

A molecular phylogenetic study of aphids (Hemiptera: Aphididae) based on mitochondrial DNA sequence analysis. Journal of Biological Research. 20. - Papasotiropoulos, Vassilis & Tsiamis, Georgios & Papaioannou, Charikleia & Ioannidis, Panagiotis & KLOSSA-KILIA, Elena & PAPAPANAGIOTOU, Aristeidis & Bourtzis, Kostas & Kilias, George. (2013). 

Interaction between phyllosphere yeasts, aphid honeydew and fungicide effectiveness in wheat under field conditions. - A. J. Dik, J. A. Van Pelt. (1992)

Insecticidal Soaps For Garden Pest Control. - Joyce D. Ubl, Carlin Munnerlin. (2019)

This article was updated November 2020.



Pyrethrum :)