White spots on fan leaves can make the leaves undesirable and they tell you that something is wrong with the plant. For example, they could indicate that your cannabis plants are being attacked by pests or are growing in the wrong growing conditions.

White Spots on Fan Leaves

Read this article to learn the exact cause of white spots on your fan leaves and how to remove them.

Why Are There White Spots on Your Fan Leaves?

There are white spots on your fan leaves because of fungal infections, nutrient deficiencies, possible sunburn and an invasion of pests. If your cannabis plants have white spots on their leaves, these are some other causes that you should watch out for to be able to treat them effectively.

– Fungal Infections

Your fan leaves can get attacked by different fungi such as the white powdery mildew fungus. This fungus starts from the base of the plant and covers the lower sides of your fan leaves with mold.

The upper sides also get spots and sometimes get covered in mold. Just like powdery mildew, fungi attack cannabis plants that are growing in the wrong environmental conditions.

What is the humidity of the room? How often do you water your plants? If you overwater your cannabis plants, you can kill their roots and fungi are attracted to dead things, as fungi are decomposers.

– Nutrient Deficiency

If you notice that your fan leaves have large pale or white spots or an entire leaf is turning pale, the plant may be suffering from nutrient deficiencies.

A deficiency of nutrients such as iron, potassium, and nitrogen can change the color of your fan leaves, as cannabis plants, just like every other plant, need nutrients to maintain the color of their leaves.

How often do you feed the cannabis plants? What type of fertilizer do you use? If you do not use a suitable or effective fertilizer for the fan leaves, they will get white or pale-yellow spots.

– Could be Sunburn

Another factor that can affect the color of your fan leaves is the exposure of the plants to the sun.

When the sunlight reaching the plant is more than what they want, their leaves will turn pale and might have pale or white spots on their tips and edges. The edges of the fan leaves will also curl up and wither, as the temperature of the sun is too high.

How exposed are your fan leaves to the sun? Are the white spots only appearing in the summer months? The answers to these questions can tell you if your fan leaves have pale or white spots because of their exposure to the sun.

Fan Leaves Have White Spots

– Pests Invasion

Pests such as spider mites and fungus gnats can attack your fan leaves, causing havoc. Spider mites cover themselves in silk, usually at the back of the leaves and this gives the leaves their white spots.

Aphids and scale insects are also white pests that you should watch out for in your cannabis plants. Weevils may not be white, but they lay white eggs on the fan leaves.

As for fungus gnats, they usually do not attack the leaves, but they can attack your plants, especially if the plants have a fungal infection. The presence of powdery mildew and fungus gnats in your fan leaves indicates that you may be overwatering your cannabis plants.

– Applying Excess Fertilizer

Even though cannabis leaves can get spots due to a lack of fertilizer, too much fertilizer can also give them white spots.

When they get more nutrients than they need, the cannabis leaves start to burn and they can get spots, especially around their edges and tips. These spots are similar to those that appear if the plants get sunburned.

An excessive amount of organic fertilizer can also attract a lot of fungi to your fan leaves. Remember that fungi are decomposers. If the organic nutrients (which are not fully rotted) are in excess, fungi such as powdery mildew will cover your plants.

– Humidity Problems

Humidity is a very important factor that you should consider if you have white spot problems in your fan leaves. Remember that fungi, bacteria, and other microbes thrive in a humid environment. This means that if the humidity level is significantly higher than what your plants need, they can get attacked by these harmful microbes.

High humidity levels also prevent the plants from excelling enough moisture from their leaves (i.e., through transpiration).

The trapped droplets in the plant’s leaves will cause plant edema and they usually show as white or pale-green spots. Plant edema is harmful, as it can lead to the bursting of your fan leaf cells.

– Light Problems

What if your cannabis plants have white or yellow leaves because of a lack of light? Even though these plants can get sunburned if they are overexposed to the sun, they can also get white or pale spots on their leaves if they do not get enough light.

Plants need light for photosynthesis and the production of chlorophyll which is responsible for their green color.

How many hours of sunlight do your fan leaves get daily? Is there a shade blocking them from the sun? Consider these things and you will know if a lack of light is responsible for the white spots in your plants or not.

– Bacterial and Viral Infections

What if the white spots on your fan leaves are caused by bacterial or viral infections? When harmful microbes like bacteria or viruses infect plants, the plants trap the infection by killing the cells in that region and stopping the flow of water and nutrients to that region. This is why the spots caused by infections look dry and are usually white, pale, or brown.

Bacterial leaf spot is a common infection that you should watch out for, especially if you prune your plants regularly. If you prune your cannabis plants with unclean tools or grow the plants in a substrate with pathogens, they can get infected.


How To Fix the White Spots on Your Fan Leaves

To fix the white spots on your fan leaves you can isolate and prune the sick plants, use hydrogen peroxide, use store-bought fungicide, use insecticidal soap, use baking soda on them, and ensure proper air circulation. Just keep in mind that you first have to diagnose the problem before treatment.

– Isolate or Prune Sick Plants

Immediately after you see that your cannabis fan leaves have white spots, you should isolate them. If you are growing them on the ground and cannot isolate them, you should prune them off the affected branches. Pruning off the leaves can help keep your healthy cannabis plants safe and free from white spots.

Do not dispose of the cut fan leaves. Instead, keep the fan leaves far from your cannabis farm and then carefully study the spots. Try to find the cause with the tips listed above or take the cuttings to experienced cannabis growers to help you identify the cause of the white tips.

Fix the White Spots on Fan Leaves

– Use Hydrogen Peroxide

Hydrogen peroxide has antimicrobial properties, so it can keep your fan leaves free from fungi and other types of infections and pests. You can rub some of this compound on the fresh wound of your cannabis plants (i.e., after pruning them) or spray the compound directly on the powdery mildew or white spots.

Get the product from a gardening store and be sure to follow the product’s instructions. Also, do not spray your fan leaves with hydrogen peroxide until the leaves start to drip or become too wet.

– Use Baking Soda

A baking soda solution is very effective against fungi and some other microbes because of its properties.

Baking soda or sodium bicarbonate is the active ingredient in some cheap fungicides, so you can use this cheap product for your fan leaves. You may already have baking soda at home. All you need is to mix it with water to form a solution that you can spray.

Spray your fan leaves with this solution regularly, especially if they have powdery mildew or other types of fungi. You can also spray healthy cannabis plants so that they can be safe from infection.

– Use Store-bought Fungicides and Anti-bacterial Agents

Just in case all the antifungal products that you have been using for your fan leaves are not giving you the expected results, you should go to a gardening store and buy store-bought fungicide.

These chemical products will surely work, especially if you use a product that is suitable for the specific type of fungi attacking your fan leaves.

You can also buy bactericides if your fan leaves are infected by bacteria. It does not matter the type of chemical product that you choose to use, be sure to follow the instructions so that your fan leaves can be safe.

– Using Insecticidal Soap

Just in case you want to prevent pests such as insects and arachnids from attacking your fan leaves, you can easily do so without cost by using insecticidal soaps.

These soaps are easy to make. You just need to collect dish soap and mix it with water. Shake the mixture thoroughly and spray the foam on the insects that are eating your fan leaves.

The insects may be stubborn, but if you use this product consistently, they will go away from your cannabis farm. Do not stop spraying the soap. If the product is not as effective as you expected, you can buy insecticides from the store.

– Ensure Proper Air Circulation

Remember that high humidity is a very serious problem for cannabis plants. To keep the plants safe from plant edema and a microbial attack, you need to grow them in a well-ventilated room. Make sure that the room is not stuffy and that the plants get enough oxygen in the atmosphere.

If you are growing cannabis plants indoors you should install a fan so that the air can easily circulate from one part of the room to the other. Please do not disturb your fan leaves by keeping the fan too close to where they are. Remember that plants hate drought caused by wind.

– Properly Feed Your Cannabis Plants

Properly feeding cannabis plants does not just remove the pale spots that they have, it can help them become strong enough to fight off infections.

Ensure that their fertilizer has enough fertilizer and potassium. Also, you can feed them with organic nutrients if you want. Just make sure that the product is properly decomposed or rotted so that it does not attract pests.

If your cannabis plants are already suffering from a deficiency of some nutrients, you can easily fix this problem by using foliar fertilizer.

Foliar fertilizer has nutrients that are water-soluble, readily available, and easily absorbed by the leaves of the plants. The use of foliar fertilizer is the quickest way to fix the nutrient deficiency.

– Dispose of Unresponsive Plants

Just in case a cannabis plant is not responding to all the treatments that you have been providing, it is best that you let it go so that it does not consume your time and money anymore.

Also, you should dispose of it so that the chances of other plants getting infected can be reduced. Do not dispose of it anywhere close to your farm.

White Spots Problem on Fan Leaves

Well, before disposing of the plant, be sure that you know the exact cause of the white spots or the illness of the plant. If you do not know the cause, you may be unable to prevent other plants from getting the same spots.


Now, you can grow cannabis plants free from white spots on their leaves.

Here are some take-home points from this article:

  • The most common cause of white spots on fan leaves is a fungal attack. Fungi such as powdery mildew attack cannabis plants often.
  • If your cannabis plants are attacked by fungus gnats, you need to check the watering rate, as you may be overwatering the plants.
  • You can make use of hydrogen peroxide or baking soda to get rid of microbial pests on your fan leaves.
  • If your fan leaves have pale or white spots due to nutrient deficiency, you should properly feed them with a nitrogen-rich fertilizer.
  • Remember that giving your plants excess nutrients can attract harmful fungi.

Growing marijuana plants is now easier for you, right? Go check your plants and fix their white spots if any.

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