If you notice tiny spots on your cannabis plant stems and leaves, you may feel like shouting “Oh Barnacles!”, like Spongebob Squarepants. And you would be right, these are nothing desirable and if left untreated could suck the life right out of your plant.

You should take quick action to remove barnacles and scale insects from your plants as soon as you notice them. While not the worst type of insect attack on cannabis, scale insects will weaken your plant if the infestation gets out of control.

How to Identify Barnacles on Your Cannabis Plants

Barnacles are scale insects that hang out under the leaves and on the stems of your plants and can appear in different patterns and colors. They might look like tiny little bugs or they could appear like growths on a plant. They can also release a sticky, sweet substance called honeydew that may cause dark patches of mold to appear and can also attract ants.

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Wax scale insects gather on the leaves and stems and will stop moving when they find their favorite spot to hang out. The scales can vary in appearance, but they all act the same with the main goal of sucking the life and energy out of your plants.

Solutions to Remove Barnacles and Scale Insects

Use a Pressure Sprayer

You can treat barnacles and scale insects in the same way that you would treat an infestation of aphids. The first thing to do is to remove the barnacles with a one-handed pressure sprayer. This is the easiest way to get all of the bugs off of your plants. You can also try to rub them off but using a pressure sprayer can remove 99% of them quickly and easily.

Using an insecticide solution with your sprayer can give you two-in-one protection, removing the scale insects and preventing a re-infestation at the same time.

Insecticidal Soaps

Insecticidal soaps or fatty acid salts can provide good protection against wax scale insects and barnacles. They are safe for use on your cannabis plants, they do not leave much residue and they weaken the outer shell of the scales. Insecticidal soaps do not stay on your plant for long, so it is important to spray with full coverage and it may be necessary to apply follow-up applications. Make sure to spray just your leaves and stems and avoid spraying any buds.

Neem Oil

Neem oil is an effective remedy against various types of bugs including scale insects and mold, although it can be harmful to humans so use care when applying. Neem oil also has an unpleasant smell and taste so just like with insecticidal soap, be sure to not get this anywhere near buds or bud development on flowering plants.


Spinosads are safe and organic products that are harmless to people, including children, and are safe for pets and plants. Spinosad can be applied liberally wherever you see scales, particularly on the underside of leaves. This is not quite as strong as some other pest control insecticides although it does work when applied with a pressure sprayer and is safe for humans, animals, and your plants.

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This insecticide is also a safe and organic mix of various horticultural oils that can be effective on scale insects and various broad mites when used regularly. This treatment does not provide long-lasting effectiveness, however, and should be applied regularly or combined with other treatment options. You should also use a one-hand pressure sprayer to apply evenly to all leaves and stems.

Treat barnacles on your cannabis plants immediately as they can reproduce quickly. Some insects like ladybugs can help to keep scale insects away by feeding on them, although introducing beneficial insects into your garden will not be enough to prevent the rapid reproduction of barnacles and scale insects.

Mosca Seeds offers the finest in quality cannabis seeds online with a wide selection of seed types and strains and more than 15 years of experience in cannabis seed genetics. It is important to keep an eye on your plants and prevent harmful insect infestations. Remember that quality plants start with quality seeds, check out the Mosca seed bank now.