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Plant Diagnosis

Cannabis plants in cultivation can encounter a wide variety of problems. Here you will be able to find pictures of common ailments and links to information and solutions pertaining to them.

Common Ailments:


-Common problem with indoor cultivation
-Curled and twisted leaves are evidence of a Ph problem
-Brown/yellow/red spots
-Progressing eventually to nutrient lockout



-Leaf margins curled upwards (Heat stress)
-Deformed leaves
-Bleaching (Heat stress)
-Slow growth
-Stems, buds, and leaves may begin to turn reddish purple (Cold stress)

Light burn:

-White, bleached portions of leaves nearest the light
-Burnt necrotic patches if the damage is severe


Over/Under watering:

-Dropping leaves
-Leaf margins curl upwards [see picture under temperature stress]
-Leaves eventually hang completely limp and get crispy to the touch (Under watering)
-Roots rot in extreme cases (Over watering)


Macro Nutrient Deficiencies:

Nitrogen (N):

-Slow stunted growth
-Progresses from the bottom upwards
-Thin, weak stems
-Pale green leaves worsening to yellow


Phosphorus (P):

-Slow stunted growth
-stem turns reddish purple starting at the leaves
-Dark brown/purple/black necrotic patches appear on older leaves radiating from the veins
-Tips turn brown and curl downwards



Potassium (K):

-Chlorosis moves upwards from older leaves rapidly progressing to necrotic lesions most visible on margins and tips
-Branches easily broken
-Stems may stretch
-Similar to iron deficiency except for curled margins and tips

(Pic: Toad)

Calcium (Ca):

-Affects new growth first
-Terminal buds and root tips die back
-Necrotic patches on margins and near leaf base

(Temporary picture, submissions requested)

Sulpher (S):

-General chlorosis (lightening of leaves while retaining green color)
-Chlorosis similar to nitrogen deficiency but appears all over plant, not concentrated in the older leaves
-Necrotic patches can appear on petiole
-Distinct pink/red coloring of underside of leaves and stems

(Temporary picture, submissions requested)

Magnesium (Mg):

-Commonly deficient in Cannabis
-Yellowing of lower leaves progressing upwards with severity
-Interveinal yellowing
-Rust brown patches on leaf margins, tips and between veins


Micro Nutrient Deficiencies:

Boron (B):

-General chlorosis visible on new growth first
-Necrosis of meristematic tissue
-Loss of apical dominance
-Hollow or roughened stems
-Similar to calcium deficiency

Copper (Cu):

-Downward curling of leaves and petioles
-Chlorosis and loss of turgor of young leaves
-Netted green veining around areas of grey-white bleeching

Zinc (Zn):

-Interveinal and/or marginal chlorosis appears on new leaves
-Pitting may occur, similar to calcium or iron deficiency

(Temporary picture, submissions requested)

Iron (Fe):

-Chlorosis occurs near base of leaves on new growth
-Interveinal regions turn pale or white but the veins remain dark green
-Bleaching continues moving down to the rest of the plant and necrotic spots appear on the leaves

(Temporary picture, submissions requested)

Chloride (Cl):

-Rarely, if ever, deficient in cultivated plants
-Chlorosis and wilting of young leaves in characteristic depressed regions
-Bronzing of the upper side of mature leaves

Manganese (Mn):

-Light chlorosis of young leaves with green veins (similar to iron deficency)
-Leaves aquire a metallic/purple sheen
-Dark grey freckles appear progressiong to necrotic regions which enlarge and eventually kill the leaf

Molybdenum (Mo):

-Initial symptoms similar to nitrogen deficiency
-Mottled leaves
-General chlorosis
-If severe, leaves develop a unique orange coloration

(Temporary picture, submissions requested)


Spider mites:

-Most common pest indoors
-Appear as small specks on the underside of leaves. Use a magnifying glass to see them and their small milky eggs
-Create minuscule webs between buds and branches
-Small white spots appear on the top of a leaf (stippling) from where they have been eating the plant

(Pic: Annom)

(Pic: Annom)

(Pic: Yrat)

(Pic: Yrat)
 <--- severe "stippling" damage from spider mites
(Pic: Yrat)

How to Kill Spider Mites - Get Rid of Spider Mite Infestation on Cannabis
(Link: Geokills)


-Tiny (<1mm), slender insects with fringed wings
-Leave observable piles of black fecal matter
-Thrips gorge the underside of the leaves and eat the contents. The upper side of the leaf becomes stippled and takes on a silvery sheen.

(Temporary picture, submissions requested)

White Flies:

-Miniscule white fly
-dusty/waxy appearance
-Fly away from shaken plants in swarms
-Premature stage appear as scales on leaves and stems
-Stippling of leaves if severe

(Temporary picture, submissions requested)

Fungus Gnats:

-Small (1-2 mm) black/brown flies similar in appearance to a mosquito
-Thrive in moist environments
-Tend to run away before taking flight if provoked
-Place a potato wedge on the soil to attract the worm like larvae and aid identification
(Temporary picture, submissions requested)


-Often unrecognized as an insect
-Immature scales lack a head or any other discernible body part but are small, round, 'humps' that cling to foliage, flowers, and stems
-The immature scale inserts a mouthpiece into the plant and may cause loss of vigor if numbers are sufficient

(Temporary picture, submissions requested)


-Stunted growth and lack of vigor
-mottled leaves (stippling)
-yellowing of leaves
-Honeydew deposits found on leaves and stems

   <- ants will often "farm" aphids outdoors
                                         (Pics: Yrat)


-Larval stage of butterflies and moths
Voracious feeders
-Can burrow into stems and buds causing many other problems including infection, and structural instability

(Pics: Simisu)


Powdery Mildew:

-Light spots appear on leaf tops
-Fine white/grey powder visible on leaves and stems
-Slow growth and loss of vigor
-Leaves eventually curl, yellow, and die

(Pic: Msmr5150)

(Pic: msmr5150)

Tobacco Mosaic Virus:

-Light green coloration radiating from veins
-Mottled mosaic pattern begins to appear on leaves
-Symptoms most apparent on young leaves
-Leaves may exhibit odd growth such as twisting, stretching, and crinkling

(Pic: Annom)

(Pic: Annom)

Stem Rot:

-Irregular black lesions around soil line
-Infected stem begins to rot
-Strands of mycelium may be visible in the decayed flesh
-Stem becomes soft and unable to bear weight

(Pic: FullySikMate)

Root Rot:

-Fungal infection of the roots general resulting from low oxygen levels, high root zone temperature, and excess water
-Roots develop an odor of decay, slimy texture, are soft and easily broken when handled
-Causes general drooping of the foliage and slows growth

(Temporary picture, submissions requested)

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