Cannabis BasicsPests and Problems

A quick guide to Diagnosing your cannabis plants problems

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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
Cannabis Boron Deficiency

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

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

Cannabis Boron Deficiency
Cannabis Boron Deficiency

Cannabis 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 growroom.

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 look out for a single dying leaf in what appears to be a otherwise normal bud.

Cannabis Bud Rot
Cannabis Calcium deficiency

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

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 Copper Deficiency

A copper deficiency is rare and manifests itself with backward curved leaves, lack of growth, and unusual dark color of the leaves. Copper does not readily move through the plant and is considered “low mobility.”

Cannabis Copper Deficiency
Cannabis Fungus Gnat Problems

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

Cannabis Fungus Gnat Problems


Cannabis 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 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.

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

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

cannabis Heat Stress
Cannabis 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
Cannabis Magnesium deficiency

A 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
Cannabis 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 start on the base of  the leaf becoming darker green towards the “fingers”.

Cannabis Manganese Deficiency
Cannabis 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
Cannabis 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
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
Over Watering Cannabis 

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.

Cannabis Over Watering
Pests Insects And Viruses 

Unfortunately, insects or pests can completely spoil your harvest marijuana.

Some insects living in the soil, while other pests are in the air. Mold can be a big problem too.

Pests that can affect your marijuana plants include aphids, spider mites, ants, whiteflies, white powdery mildew / mold white powder, stem rot , and even mammals like moles and rats.

Pests Insects And Viruses
Cannabis PH Fluctuations

The 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 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.

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


Cannabis PH Fluctuations
Cannabis 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.

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.

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.

Cannabis 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. 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.  .

Cannabis root rot

Problem: The roots need water, but if they are exposed to water with bacteria they will start to rot. Roots grown in poorly drained soil, too much water and without enough oxygen available are much more susceptible to problems.

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

The plants affected by root rot begin to lose their leaves, turn yellow, fall, wither , and it seems that they are dying.  One of the biggest causes of root problems in hydroponic systems is having the nutrient solution at a high temperature.  Ideally try to keep your nutrient temps below 74f.

Spider Mite Damage

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

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 a grower marijuana in soil.

Cannabis Sulphur Deficiency

A sulfur deficiency manifest 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 leafs, a deficiency of sulfur will start on the back of the leaf and move their way forward instead of starting at the tips.

Over and under-watering

Problem: If your plant is wilted, then it usually is a sign of either over or under – watering

In soil lift the pot before any watering, this will help make sure you do not give the plants water when they dont need it.  Over watering is often a much more serious problem than under watering.


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.


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 flowering stage, the flowers may begin to die.





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