Pests and ProblemsCannabis Basics

A Quick Guide To Diagnosing Your Cannabis Plants Problems

Use the following photos to quickly diagnose your Cannabis plants!

Although many of the problems of the marijuana plant are really related to problems with the pH.

Here are pictures to learn about the problems, deficiencies, or symptoms.

A quick guide to Diagnosing your cannabis plants problems
Boron Deficiency

Problem: A boron deficiency in cannabis is relatively rare, and usually accompanied by other types of nutrients or pH problems

boron deficiency on cannabis bud
boron deficiency on cannabis bud

The first signs of boron deficiency are abnormally growing tips, together with brown spots on the leaves.

Cannabis Boron Deficiency
Cannabis Boron Deficiency


Flush your plant with clean, high-quality water (wash the soil) add half the normal dose of nutrients to the pH-adjusted (or normal-quality quality) water, and monitor the health of your flower’s newly developing branches and leaves.

Bud Rot

Usually, a bud rot infection is visible in only some parts. Sometimes just the largest and densest buds are affected, but other times you will get patches throughout the plant, especially after a few days of rain or in a humid grow room.

You can see areas (in buds, pistils, and/or leaves) they are dark, discolored, and/or dry, unlike the rest of the plant. One of the early signs I lookout for a single dying leaf in what appears to be an otherwise normal bud.

bud rot infection
bud rot infection

Cannabis Bud Rot


Improve airflow in your grow area, bud rot thrives in damp humid conditions with poor airflow.  Large dense buds are also more prone to bud rot so if you are growing a large yielding strain consider training or topping your plants to produce smaller buds but more of them. This will help to reduce the chances of you having problems.

Calcium deficiency

Calcium is an important nutrient that helps provide the structure of the cannabis plant and resist heat stress

cannabis calcium deficiency
cannabis calcium deficiency

A calcium deficiency can sometimes be difficult to diagnose because calcium deficiencies often are accompanied by magnesium, iron, and/or other deficiencies.

Cannabis Calcium deficiency

Cannabis leaf Calcium deficiency


If the pH in the root area of ​​your flower is bad, it means that cannabis is not able to absorb calcium properly. The first step is to make sure you have the correct pH values ​​in the growing area.

Each cannabis variety has its own unique nutritional problems. However, calcium, magnesium, and iron problems often occur in cannabis at the same time.
Pro growers supply a supplementary nutrient that provides CaMg (Calcium Magnesium) while also supplying fertilizers. In this way, they prevent such deficiencies. If you do not have such a complement until now, you will observe healthy growth within a week when you supply it immediately and give it to your plant.

Copper Deficiency

A copper deficiency is rare and manifests itself with backward-curved leaves, lack of growth, and unusual dark color of the leaves.

Cannabis copper deficiency
Cannabis copper deficiency

Copper does not readily move through the plant and is considered “low mobility.”

Cannabis Copper Deficiency

Cannabis copper deficiency


You flush (wash) your system well with water with good pH value. You feed the flower half of the right fertilizer it needs. Observe the plant cleans itself in a few days.

Fungus Gnat Problems

A fungus gnat infestation of your cannabis plants can cause all kinds of strange problems – often seen as overwatering, pH issues, or nutrient deficiencies. See damaged leaves and reduced growth rates.

Cannabis Fungus Gnat Problems


To prevent the fungus gnats from appearing in the soil, avoid overwatering: the soil must not remain impregnated with water and you must not water before it has dried well on the surface.

Check the environmental humidity in your grow room: if it is excessive, it creates the ideal substrate for the gnat. keep the ambient temperature below 24 ° C . Do not use cheap soils because they usually contain undecomposed materials liked by the midges.

Once established, the gnat does not go away by itself unless the soil is completely dried out. To combat it, first, reduce watering and/or ambient humidity. Sprinkle the substrate with vermiculite, an inert product that makes it difficult for female gnats to lay eggs.

Place the yellow adhesive strips to capture the adults, attracted by the color. Sprinkle a product based on Neem oil, or Bacillus thuringiensis, on the soil. If none of these measures give the desired results, repot the plant in another pot, carefully eliminating most of the damp soil and replacing it with new quality soil; discard the old soil, and wash the old pot with water and bleach (10: 1).

Hydrogen peroxide

  • It can be used as a soil soak or in hydroponic systems.
  • The peroxide solution kills the fungus fly larvae on contact.

Neem Oil

  • Effective soaking the soil to combat mushroom gnat larvae
  • Spraying can keep adult midges at bay

Heat Stress

Your cannabis plant can only withstand a certain amount of heat and light. After a certain point, your cannabis plant will begin exhibiting signs of stress

Cannabis heat stress on leaf
Cannabis heat stress on leaf

in leaves near the light source and / or heat. Its leaves will become yellow or brown with brown spots and it may appear generally burned in places where there is too much light.

crispy cannabis leaves due to heat stress
crispy cannabis leaves due to heat stress

Important for hydroponic growers! High temperatures can cause root rot, a serious problem that can kill plants quickly.

Cannabis also shows heat stress when grown outdoors in hot, dry weather, especially when it is not given enough water.

cannabis Heat Stress


Find a way to lower the heat. Rearrange the air circulation inside as it should be. If you are giving out too much light, reduce the amount of light you give off. replace your lamp and system. Or move your lamp higher than the top of your flowers. When you get the ideal temperature, humidity, light system for optimum growth, set up a system that will protect it.

Iron Deficiency

An iron deficiency in cannabis is relatively rare, and symptoms appear more often than not along with other nutrient problems or deficiencies

The main symptoms of iron deficiency are:

  • Yellowing of upper leaves
  • Yellowing of the smaller inner leaves
  • The veins of the leaves remain green

Cannabis Iron Deficiency


Iron deficiency is an unlikely problem as long as you keep the pH below 6.5 (5.7 for Hydroponic or rock wool). If too much Phosphorus (P) is given, it will cause the iron to remain in the system.

The best thing you can do is to check the pH values ​​in the system. If necessary, you will flush the system with clean and pH-regulated water. Then you start with the required (correct) nutrients at half the scale.

Another disadvantage of the iron remaining in the system is that it sticks to other nutrients and locks them in the system. If you are adding iron to your system, do not give fertilizer to your system during that irrigation. Also, pay attention to whether there is iron in your fertilizer.

Magnesium deficiency

Green color or light yellow will start showing in the veins and the edges of the lower and larger leaves this is one of the classic signs of deficiency magnesium in cannabis.

Cannabis Magnesium deficiency


You can avoid magnesium deficiency by observing and maintaining the correct pH balance (between 5.5 and 6.5) If you continue to add additional magnesium while magnesium remains in the system, it will worsen the situation. Unless you balance the pH value, your plant will not be able to draw magnesium from the system.

FLUSH the system properly (with pH balanced water). Feed half the normal value and observe whether the newly developing leaves and branches are increasingly healthy.

Manganese Deficiency

The leaves can become yellow between the veins, speckled with brown spots on the affected leaves. These brown patches can spread and eventually kill the leaf. If handled the leaves can also be easily crushed and fall apart between your fingers.

The overall growth of the marijuana plant can be stunted. With a manganese deficiency, yellowing starts on the base of the leaf becoming darker green towards the “fingers”.

Cannabis Manganese Deficiency


Manganese deficiency usually occurs when pH values ​​are too high or when the plant starts taking up too much iron. We clean your system thoroughly by FLUSHING with balanced pH water. Feed half the normal values. Observe carefully whether your system, your plant, is being cleaned and renewed in a day or two.

Molybdenum Deficiency

Initial symptoms may be similar to nitrogen deficiency (yellowing of the lower leaves). The leaves may become mottled or stained. However, the telltale sign of a molybdenum deficiency is that leaves may begin to show orange, red or pink around the edges and begin to move toward the center of the leaf. Sometimes the color appears in the middle of the leaves as opposed to the edges.

Cannabis Molybdenum Deficiency


 FLUSH system with clean balanced pH water. Start feeding at half a scale. Observe if the problem has started to clear in a few days. Molybdenum can remain locked in low pH soil or hydro systems. (It may get stuck in the system between 5.5-6.0) It is recommended to keep your pH value slightly above this.

Nitrogen Deficiency

A nitrogen deficiency will make the older, lower leaves on your plant to turn yellow, wilt, and eventually die

Yellow leaves may turn brown and usually become soft before turning crisp and falling off the plant on their own.

Cannabis Nitrogen Deficiency


Simply feed your plants with high-quality cannabis nutrients. You will find that the plant starts to recover immediately by giving the correct strength of nutrients. For soil growers, the same advice applies but the time for the plant to show signs of recovery will be slightly longer. Try to use good organic fertilizers whose values ​​are adjusted for the needs of cannabis.

Nitrogen Toxicity

leaves dark green, weak stems, and slow overall growth. Marijuana leaves with toxic nitrogen often acquire a “Claw” at the ends. They have a strange curve / or cupping that is often confused with excess water.

leaves that become claws begin to turn yellow and die if the toxicity of nitrogen is not addressed, unlike nitrogen deficiency. You can tell if the problem is caused by an excess of nitrogen because the rest of the plant will be dark green, and the yellow leaves will become claws.

Cannabis Nitrogen Toxicity


So the N ratio in your fertilizer is too high. Reduce the amount you give while feeding. If you are using a hydroponic system you can half the nutrient feed.  For soil growers give the root zone good flushing with plain water. make sure you allow the root zone to dry out before watering again.

Cannabis PH Problems.

PH management is crucial for cannabis plants to absorb nutrients through their roots. When the pH around the roots jumps up and down, this can alter the plant and cause brown spots to appear on the leaves. This is more common in hydroponics configurations (where the pH tends to go up and down), but can occur in the soil.

Cannabis thrives with a slightly acidic root zone.  The range that your cannabis will tolerate before showing Ph problems is a Ph of 6.0-7.0 for soil and for hydro and coco a slightly lower Ph of 5.5-6.5.

Some leaves in the middle or bottom of the plant show light brown spots or brown.

Cannabis PH Fluctuations


ph meter
ph meter

The first step should be to make sure you have an accurate means of testing your Ph. This could be by using a ph meter. 

Cheap PH test kit
A cheap PH test kit 

Or by using the much cheaper and always accurate PH test kits. 

Most good quality cannabis feeds are already adjusted to give you the correct Ph. If you are experiencing problems it is usually due to something going wrong in your grow environment. Keeping soil and hydroponic systems well-aerated as well as cool will eliminate most if not all of your Ph problems.

I have first-hand experience of growers using Ph up and down chasing the perfect Ph range when all they had to do was get the root zone well aerated and cool (especially important in hydroponic systems) and make sure your hydroponic tank is kept free of dead leaves roots etc. Aim for a root zone temperature between 65°F (18°C) and 68°F (20°C). 

Phosphorus deficiency

Phosphorus (P) is used by your cannabis plant in all stages of growth. It is one of the 3 main nutrients (N-P-K) listed on the front of most bottles of nutrient and phosphorus will be represented by the second number.

Cannabis Phosphorus deficiency on leaf

Deficiencies of phosphorus in the vegetative stage usually appear at the bottom of the plant in some of the older leaves, and gradually rise up the plant if not controlled.

Phosphorus deficiency on cannabis leaf

When there is a deficiency of phosphorus lower sometimes leaves turn dark green, sometimes with a bluish tint or bronze, and the leaves can be folded down before displaying violet or dark gray patches. Sometimes the stems of affected leaves turn red or bright purple.



Control the pH balance and flush your system with a balanced pH. Iron and Zinc excess in the system leads to Phosphorus deficiency. If it continues after flushing, try adding more Phosphorus to the system. Remember, Cannabis loves Phosphorus.

Potassium deficiency

Older leaves turn yellow and then become brown and dry around the edges of the leaves. Plants can stretch and stems can become weak.

Potassium Deficiency. on cannabis plant
Potassium Deficiency. on cannabis plant

The symptoms are very similar to an iron deficiency, except that the tips of the leaves are curved and have burned edges before the leaf dies.  .



Potassium cannot be absorbed properly when there is too much calcium or nitrogen in the system. Check the pH, and if necessary flush your system, feed half the normal values, and observe if recovery is taking place.

Root rot

Problem: The roots need water, but if they are exposed to water with bacteria they will start to rot. When roots grow in poorly drained soil, too much water and without enough oxygen available are much more susceptible to problems. This is one of the main problems encountered in hydroponic systems amongst novice as well as experienced growers.

Healthy roots are white while affected by root rot are brown or cream-colored and may even smell of mold or putrefaction.



Getting rid of root rot and curing the plant is a very difficult process. Most growers prefer to ditch the plant and start over instead of trying. However, it is also possible to get rid of root rot with some tried-and-tested techniques.

You can take two approaches. First, you will directly intervene in the roots of the plant and completely change the growth environment of the plant which is causing the decay or eliminate the causes. Otherwise, the same problem will arise every time. The rotting of the plant roots is a problem that occurs not with good care, but with neglect.

Therefore, it is very important that you make every effort to control the root environment of your plant. In this way,  Remember, rotten roots never heal, just as leaves that have lost their health will never recover again. What you are trying to do is try to develop a new and healthy root.

Always keep your growing area as clean as possible. In this way, you will stop the growth of bacteria before they even start. Before you start growing, CLEAN your growing room SAFELY! Sterilizing your entire growing area prevents bacteria from settling.

Some growers add antibacterial root enhancer formulas to their feed water. These prevent the growth of root bacteria and allow the nutrients to be absorbed more easily by the flower. Some of these formulas are branded as Piranha, Aquashield, VooDoo Juice, Great White (an expensive but highly recommended brand), Subculture B, Rooters, and Plant Savers. Most of them can be used in both Hydro and soil grows.

If you are growing with a Hydro system, it is a great benefit to change the water in your tank regularly. I would seriously recommend changing it at least once a week. In this way, the plant will receive nutrients in a better way. In addition, 

How much oxygen is dissolved in water is directly related to the health of our plant. The best idea would be to buy a bigger air pump and an air stone for your hydro system. Root pathogens cannot develop in oxygen-rich environments. 

Pay close attention that the temperature of your water does not become warmer than comfortable room temperature. Relatively warm waters carry less oxygen than cold water and create a more suitable environment for bacteria to thrive. The temperature of your water in your tank should be between 18 ° C-22 ° C.

Do not allow dead roots, leaves, or plant waste particles to accumulate in the tank in the hydroponic system.

NEVER ALLOW LIGHT INTO YOUR ROOTS OR WATER IN YOUR TANK! This results in heat and a suitable environment for bacteria to thrive!

Zamazingo called SM-90 can be applied to the roots. Its roots increase health, as well as killing many bacteria and pathogens, as well as making the nutrients you give more easily absorbed by the plant. If this is sprayed on the leaves, it is effectively used against aphids, red spiders, white powder molds on your plant. 

 Spider Mite Damage

spider mites are part of the family of mites and relate to ticks and other mites.

red spider mites covering leaf
red spider mites covering leaf

mites are common pests in marijuana, especially when grown in the ground. They are less common in hydroponic configurations as there is less dead organic matter, however, we can find spider mites in any plant.

Mites are the worst nightmare of grower marijuana in soil.



As with all parasites, it is better to be safe than sorry. Avoid excess nitrogen in the fertilizer, as it attracts the red spider and other pests.

In outdoor growing, locate marijuana plants away from other plants, which may have red spiders even during the winter. They usually live in terrace or balcony plants.

In indoor crops, it is necessary to provide adequate ventilation and extraction to avoid excessive temperatures that strongly favor the colonization of the crop by the red spider. 

Spider mites don’t multiply in large numbers in high humidity, which is why it usually attacks plants with dry soil and poor irrigation.

Periodically check the plants to detect the presence of the red spider in the adult stage, or eggs, on the underside of the leaves.

Neem oil 
remains one of the best repellents we can use, it is completely natural ( 100% BIO ) and it is also very cheap to buy. Just spray your plants with water and a little diluted  Neem oil, every fifteen or twenty days to keep spider mites, whitefly and greenfly as well as many other insects well away.

My personal favorite for eliminating insects on cannabis plants is liquid horticultural soap. Soaps dry the insect out killing them very quickly without harming the plants. Horticultural soap is totally safe and very easy to use.
If you have just finished a crop with the presence of the red spider it is recommended to clean the environment well before placing the new plants.

Sulphur Deficiency

A sulfur deficiency manifests as chlorosis over the entire surface (yellowing leaves), usually starting with the newest leaves and initially can appear to be a nitrogen deficiency.

The leaves can take a red or pinkish-orange. The buds on a flowering plant can start dying. Unlike most other deficiencies that cause chlorosis of the leaves, a deficiency of sulfur will start on the back of the leaf and move their way forward instead of starting at the tips.



Control the pH balance and flush your system with a balanced pH. Too much Iron and Zinc in the system lead to Phosphorus deficiency. If the problem continues after flushing, try adding more Phosphorus to the system. Remember, Cannabis loves Phosphorus.


After watering your leaves start to wilt. Usually, fallen leaves will seem firm (the whole plant can be wilted), not only the extremities, which is often a sign of toxicity nitrogen). Cannabis plants with excess water can also show chlorosis (yellowing of leaves).

Excess irrigation does not always mean that you have been giving too much water to your plant. It often means that you have simply been giving the plant water too often, or you are growing your plants in an environment without adequate drainage.

overwatered cannabis plant
overwatered cannabis plant

If you constantly over- or under-irrigate, the leaves will fall. When you over water, the leaves will curl down with their stems.

overwatered cannabis plants

 You can also see that the leaves turn yellow. It draws oxygen from water by using plant roots. When you water too much, the plant and its roots will be sitting in still water with no oxygen left. The reason why the leaves and branches fall off is basically the roots remain OXYGEN-FREE.

 Overwatering is often a much more serious problem than under-watering.




The fastest and best thing to do is to leave your flower alone for recovery without watering. You can increase the temperature, increase air circulation, check whether the holes in the bottom of your pots are wide enough (you should have done this in the first planting),

Then, with less watering than your normal watering, you will start to give your plant the necessary nutrients again. 

The best method of growing with soil is to control the humidity in the pot by inserting your finger into the top edge of the pot. If the soil is dry, add water as simple as that.

The way I do it is to simply lift the pot and feel the weight.  There is a big difference in weight between a dry pot and a watered one. Once you are used to doing this you will never have an over or underwatered plant again. 

Under Watering

Problem: If your plants are starting to look exhausted, are drooping, and sluggish, the certainty is that you never watered it over-watering. So I don’t need to say that you need to give more water, but we wrote down it. If you water your plants less, your plants will appear lifeless and sluggish pulp.

underwatered cannabis
underwatered cannabis

underwatered cannabis plant
underwatered cannabis plant


For plants that have been dehydrated too much, it is good to wait for the water to absorb after watering. The best thing is the finger test method. Check the humidity every 2-3 days by inserting a fingering the top edge of the pot.

White powdery mildew

White spots on your leaves? The leaves are dusted with round patches of dust that looks like flour? It could be white powdery mildew.

White powdery mildew
White powdery mildew



Unfortunately, once your plants have been infected by this fungus, it is difficult to eradicate, but you can prevent it by taking certain precautions to prevent it from occurring.

  1. In your grow cabinet, instead of plants that come into contact with each other in a cluttered way, grow plants that are spacious and independent from each other and at a distance.
  2. Irrigation in the light rather than the dark period to prevent high humidity once the lights turn off.
  3. Pruning of unnecessary leaves on plants, especially the ones that dont receive light under the canopy.
  4. Good quality air circulation, both by extraction and movement of air by means of a fan.
  5. Keeping humidity levels under control. 

Treatments include using a teaspoon of baking soda to a liter of water and use it as a preventive measure.

Other options include neem oil or a sulfur burner

Zinc deficiency

Problem: Younger leaves start to by yellowing between the veins. The tips of the leaves begin to fade and die. The plant will stop growing vertically. There will be much less space between the new nodes that will mean all the new leaves are grouped together. If the plant is in the flowering stage, the flowers may begin to die.



Flush the system just as I have described many times above. Give the system less fertilizer (including zinc, iron, and manganese) it needs. Observe the plant’s recovery closely for fresh growth.

Vital Elements For Cannabis.

Vital Elements For Cannabis.

The basic nutrient requirements of plants do not change. Plants need 16 different elements to grow properly.

Three of them – oxygen, carbon, and hydrogen – are obtained by the plant from the environment, but 13 of the rest must be provided by soil, fertilizers, or various organic materials.

Besides sunlight, oxygen. carbon dioxide and water, there are thirteen essential nutrients for plants. They were divided into:

Mesoelements – Mg, Ca, S (magnesium, calcium, sulfur)
Macroelements – P, N, K (phosphorus, nitrogen, potassium)
Trace elements – B, Zn, Cu, Mo, Fe, Mn, Cl (boron, zinc, copper, molybdenum, iron, manganese, chlorine).

Macro- and microelements are needed by the plant in the greatest quantity, because they are a component of many plant components, including nucleic acids, proteins, and chlorophyll. They are important for plant respiration and the maintenance of osmotic pressure.

The main role of trace elements is that they are contained in those enzymes that are catalysts for biochemical processes. If the plants lack any trace elements, then this will lead to a decrease in yield and a number of diseases. Trace elements accelerate plant growth and increase plant resistance to adverse conditions.

All plants constantly need several basic elements that they need for proper growth: potassium, nitrogen, and phosphorus. And also plants need numerous trace elements. Modern fertilizers already contain the required amount of these elements in different quantities.

Each of these elements has different properties that help plants grow and develop. In general, nitrogen stimulates vegetative growth, phosphorus promotes proper root and flower growth, potassium helps root development and promotes photosynthesis. 

It follows that fertilizers with a sufficiently high nitrogen content are suitable for plants for vegetative growth, and fertilizers with a high phosphorus content are suitable for flowering.

Essential Nutrients for Marijuana

Nitrogen (N), potassium (K), and phosphorus (P) are the main nutrients for marijuana, so they need the most for your plants to thrive.


Phosphorus (P) is an important element in the conversion of solar energy into chemical energy. This element participates in the formation of wax, oil, and terpenes, and it is they that give marijuana its unique aroma. It is essential for the growth of plants and the strengthening of their immune system.


Nitrogen is an essential element for enzymes and proteins, as well as chlorophyll (the green pigment in plants that is responsible for photosynthesis and their color).


Plants need potassium for photosynthesis, the formation of plant proteins, and flowers.

Secondary substances for the nutrition of marijuana.

The next most important elements are magnesium (Mg), calcium (Ca), and sulfur (S). Calcium is an integral part of the structure of the cell wall. This element ensures the retention and transportation of other useful plant nutrients, as well as the resistance of plants to negative external influences.


Magnesium is essential for photosynthesis and is found in chlorophyll in all green plants. It activates numerous enzymes that plants need for healthy growth.


Sulfur helps in the production of proteins, vitamins and enzymes. This element is needed for healthy and fast growth of roots and seeds.

Amino acids and vitamins

Many growers use them when growing marijuana to increase plant growth.

Trace elements

These elements are just as important as others, but marijuana requires only very small amounts in order to grow and function properly. These elements include zinc (Zn), iron (Fe), boron (B), copper (Cu), chloride (Cl), and manganese (Mn).

Humic and fulvic acids

Often I hear people talk about them as completely different substances, but the so-called fulvic acids are a subgroup of humic acids. The addition of humic acids helps boost the growth of marijuana. They are natural regulators of plant growth and cell development.


Molasses is a fairly popular supplement due to its low price and high content of trace elements, phosphorus, iron, and carbohydrates. Molasses feeds the soil with beneficial bacteria. The keyword here is soil. Molasses cannot be used in a hydroponic system.


Cannabis Sativa, Cannabis Indica, and Cannabis Ruderalis: Thank you for being the “Gateway drug” to perpetual inspiration, compassion, benevolence, and medicinal miracles: Cannabis grower, photographer with a long experience in cannabis cultivation. His articles are journalistic reports of places where cannabis is already legally cultivated and owned. They are intended to give an impression of the wide range of cannabis cultivation. These reports are intended to help identify the truth about cannabis and reduce prejudice.

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