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Cannabis Pests - Mealy Bugs

Created by
JoshuaHolt JoshuaHolt
Added 28 December 2020

Cannabis Pests Mealy Bugs

Any destructive cannabis pest needs dealing with, and mealy bugs are no exception. Fortunately, mealy bugs make themselves quite obvious and there are a few effective techniques to get rid of them. This article should answer all your questions and help you on your way to stopping mealy bugs.

What Are Mealy Bugs?

What Are Mealy Bugs?

Mealy bugs (pianococcus citri) are soft, scaled, cottony-looking insects that come from the Pseudococcidae family. They are mostly white and have oval shaped bodies (approx 1cm) surrounded by tiny hairs. Mealy bugs group themselves together in clumps and feed off the sap in the stems of cannabis and many other species of plant.

Male and female mealy bugs look different. The males have longer, thinner bodies and have wings in order to fly and mate with females. It is rare to see the males and most infestations comprise mostly of females.

Mealy bugs are mostly seen in outdoor gardens but it does happen that they find their way indoors. Mealy bugs cause direct damage with their piecing mouths through feeding and also by excreting a sticky substance called honeydew, which is known to attract other pests or encourage black, sooty mold to grow.

Mealy Bug

Apart from honeydew, mealy bugs leave behind a white, fluffy substance that resembles something like mold or clusters of web. Before building up in large quantities, this residue can sometimes look like powdery mildew. It is the same substance they create as they feed or for laying eggs, which acts as a protective layer from predators and the environment. 

The Causes of Mealy Bugs

Ants Protect Mealy Bugs

Mealy bugs do not like the cold and tend to appear when the temperatures are warm. They also favour humid conditions, meaning they are often found hiding in areas where small pockets of air collect around the plant, such as crevices around the stems and nodes.

The presence of ants can also be a cause of mealy bugs. Ants often arrive because of honeydew, which in turn can attract mealy bugs. This can be an indication there is already another pest present that also excretes honeydew. Once the ants arrive, they protect the mealy bugs and create a safe environment for them feed and breed. If there aren't ants, it's quite unlikely mealy bugs will appear.

Identifying Mealy Bugs

Mealy Bugs Clustered Together

Mealy bugs are easy to see before they cause too much damage to your plants. However, a cannabis plant will begin to show some unhealthy signs if the pest isn't swiftly removed. The leaves of the plant will always give you an indication there is an issue that needs attention.

A cannabis plant can deal with a small infestation but when the problem gets out of hand, getting rid of mealy bugs without damaging the plant further becomes a bit more of a challenge.

If you notice honeydew on your cannabis plants, make sure to check that there aren't aphids or other pests that also produce it. As we just mentioned, honeydew can eventually attract ants and therefore mealy bugs. Sooty mold also develops because of honeydew, which spreads over the leaves, preventing the plant from photosynthesising.

Mealy Bug Damage

Symptoms of Mealy Bugs:

  • Drooping, wilting leaves
  • Slow growth
  • Leaves eventually die and fall off
  • White, cottony web around stems or leaves
  • Ants present around the grow area
  • Honeydew or sooty mold

Mealy Bug Treatment

Mealy Bugs

There are plenty of treatments for mealy bugs that do not involve the use of chemicals. Most of them can be eradicated with water or oil based sprays.

Mealy Bug Treatment

Dealing with mealy bugs can be a pain and plants generally require multiple treatments that need applying on a daily basis. At the very least make sure you are checking your plants every day after you notice the mealy bugs so you can gauge and control the infestation.

Remove Bugs By HandUsing a cloth or tissue paper, you can simply detach most of the mealy bugs by hand. Throw them in a bucket of soapy water to kill them. Soak the cloth in a diluted alcohol solution for a more effective treatment.
Clean The Plant Giving the affected areas a spray down with a hose (be careful not to use too much pressure) can help to remove a lot of the mealy bugs but further treatment is recommended.
Neem OilRecommended if you have already applied the first two treatments. Best used as a foliar spray in combination with a potassium soap (described below) every 3 days. Ideal as a preventative treatment during vegetation but can be used in flowering up until the last 3 weeks, being careful not to spray flowers.
Insecticidal SoapA useful product to have on the shelf for treatment against many cannabis pests. Attacks the outer tissues and membranes of some insects, including mealy bugs. Insecticidal soap contains potassium salts made up of fatty acids and doesn't leave residue, making it safe to use.
Alcohol SolutionA diluted isopropyl alcohol solution (1 part rubbing alcohol to 9 parts of water)can applied directly onto the mealy bugs. The alcohol dries out the mealy bugs' protective outer layer, eventually killing them.
Diatomaceous EarthDiatomaceous earth is an organic, fine powder made up of fossilized sea shells. It desiccates and destroys the scaly, soft body of mealy bugs. The tiny grains also get stuck in the joints between the scales, puncturing the shell.
Natural PredatorsLadybugs are known to be effective predators that have an appetite for mealy bugs. However, there is one specific kind of ladybug you may want to look into with the name Cryptolaemus montrouzieri. Be sure to apply sprays before introducing predators to avoid killing them as well.

 

Cryptolaemus montrouzieri

If the infestation is completely out of control, you may want to prune off entire areas of the plant or consider discarding the whole thing. It might be a better solution than trying to fix a lost cause. However, treatments are always worth a go and you can save your plants from a mealy bug infestation.

Tips For Preventing Mealy Bugs

Tips For Preventing Mealy Bugs

Although it is difficult to prevent or predict a mealy bug infestation, we should always be on the lookout and do everything we can to keep our plants in a clean, safe and healthy environment. 

Check out the GrowDiaries link up the page to see how IslandP dealt with mealy bugs.

The top priority when avoiding pests all together is maintaining the proper temperature, humidity and ventilation. Whether you are growing indoors or outdoors, there are some prevention techniques that can help to minimise the chances of mealy bugs finding their home in your cannabis garden.

  • Daily checks for signs of pests.
  • Maintain temperatures within the comfortable range of 20-25°C.
  • Circulate the air in the grow room and replenish at least once every 2-3 minutes.
  • Do not let relative humidity exceed 65%.
  • Look out for honeydew and ants.
  • Apply neem oil + insecticidal soap preventative treatment during vegetation (best in the morning).
  • Always maintain a clean space and remove any dying or decaying plant material.

Neem Oil

If you found this article useful or have any tips regarding mealy bugs on cannabis plants, why not drop a comment to help out other growers?

External References

Citrus Mealybug, Planococcus citri (Risso) (Insecta: Hemiptera: Pseudococcidae). - Kaur, Harsimran & Goyal, Gaurav & Gillett-Kaufman, Jennifer. (2012)

Host plants, geographical distribution, natural enemies and biological studies of the citrus mealybug, Planococcus citri (Risso) (Hemiptera: Pseudococcidae). - Noha H. Ahmed and Shaaban M. Abd-Rabou (2010) 

Management Strategies Of Mealy Bug: A Big Thread To Agriculture. - Diwan, Garima & Lal, Narayan & Sahu, Nisha. (2020). 

This article was updated December 2020.






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