Cannabis Pest & Disease Management Guide

Identify and effectively treat common cannabis pests and diseases with this comprehensive guide. Early detection and proper treatment are key to maintaining a healthy garden. For nutrient deficiencies and growing issues, see our Plant Problem Diagnosis Tool. Need personal help with identification? Ask our AI Herbal Advisor

Spider Mites

Severe

Symptoms

Tiny yellow/white speckling on leaves (stippling)
Fine webbing between leaves and branches
Bronzing or yellowing leaves
Visible tiny moving dots under magnification

Treatment

Biological: Predatory mites (Phytoseiulus persimilis)
Organic: Neem oil, insecticidal soap
Commercial: Spinosad products
DIY: 1:10 alcohol/water mix with few drops of dish soap

Prevention

Maintain 40-60% humidity (mites prefer dry conditions)
Regular leaf inspection (especially undersides)
Quarantine new plants before introducing to grow area
Preventative release of predatory mites

Aphids

Moderate

Symptoms

Clusters of small green, black, or white insects
Sticky residue on leaves (honeydew)
Curling and yellowing leaves
Stunted growth of new shoots
Black sooty mould growth on honeydew

Treatment

Biological: Ladybirds, lacewings, parasitic wasps
Organic: Neem oil, insecticidal soap
Commercial: Pyrethrin-based products
DIY: Strong water spray to dislodge, then soapy water application

Prevention

Regular inspection of new growth and leaf undersides
Yellow sticky traps to monitor population
Companion planting with catnip, garlic, or chives
Maintain plant health and proper nutrition

Powdery Mildew

Moderate

Symptoms

White powdery substance on leaves, stems, and buds
Typically starts on upper leaves, spreads downward
Yellow spots on leaves below powder
Twisted or distorted new growth
Reduced photosynthesis and vigour

Treatment

Biological: Bacillus subtilis sprays
Organic: Potassium bicarbonate solution, milk spray (1:9 milk/water)
Commercial: Green Cure, Lost Coast Plant Therapy
DIY: Baking soda solution (1 tbsp per gallon of water with few drops of dish soap)

Prevention

Improve air circulation in grow area
Maintain humidity below 60%
Avoid wetting leaves during watering
Remove affected leaves promptly
Use silica supplements to strengthen plants
Consider using powdery mildew resistant strains

Tobacco Mosaic Virus

Moderate

Symptoms

Mottled green-yellow pattern on leaves
Twisted, distorted leaf growth
Stunted growth and reduced yields
Yellow or light green spots/streaks
Symptoms may appear similar to nutrient issues

Treatment

No cure available: Remove and destroy infected plants
Quarantine: Separate affected plants immediately
Disinfect: Clean all tools, pots, and surfaces with 10% bleach solution
Prevention: Only viable approach once identified

Prevention

Wash hands before handling plants
Don't smoke or handle tobacco near cannabis plants
Disinfect tools between plants
Use clean, new growing medium
Quarantine new plants for observation
Remove weeds that might harbour the virus

Spider Mites

Severe

Symptoms

Tiny yellow/white speckling on leaves (stippling)
Fine webbing between leaves and branches
Bronzing or yellowing leaves
Visible tiny moving dots under magnification

Treatment

Biological: Predatory mites (Phytoseiulus persimilis)
Organic: Neem oil, insecticidal soap
Commercial: Spinosad products
DIY: 1:10 alcohol/water mix with few drops of dish soap

Prevention

Maintain 40-60% humidity (mites prefer dry conditions)
Regular leaf inspection (especially undersides)
Quarantine new plants before introducing to grow area
Preventative release of predatory mites

Aphids

Moderate

Symptoms

Clusters of small green, black, or white insects
Sticky residue on leaves (honeydew)
Curling and yellowing leaves
Stunted growth of new shoots
Black sooty mould growth on honeydew

Treatment

Biological: Ladybirds, lacewings, parasitic wasps
Organic: Neem oil, insecticidal soap
Commercial: Pyrethrin-based products
DIY: Strong water spray to dislodge, then soapy water application

Prevention

Regular inspection of new growth and leaf undersides
Yellow sticky traps to monitor population
Companion planting with catnip, garlic, or chives
Maintain plant health and proper nutrition

Broad/Russet Mites

Severe

Symptoms

Twisted, distorted new growth
Leaves appear wet or glossy, often with blistered appearance
Stunted growth and yellowing leaves
Microscopic mites barely visible even with magnification
Bronzing of leaves and flowers

Treatment

Biological: Predatory mites (Neoseiulus species)
Organic: Sulphur sprays (veg stage only)
Commercial: Products containing abamectin or spiromesifen
DIY: Apply treatment at multiple intervals, as eggs may survive

Prevention

Strict quarantine of all new plants
Maintain clean growing environment
Regular inspection with 60-100x microscope
Avoid excessive heat which speeds development

Powdery Mildew

Moderate

Symptoms

White powdery substance on leaves, stems, and buds
Typically starts on upper leaves, spreads downward
Yellow spots on leaves below powder
Twisted or distorted new growth
Reduced photosynthesis and vigour

Treatment

Biological: Bacillus subtilis sprays
Organic: Potassium bicarbonate solution, milk spray (1:9 milk/water)
Commercial: Green Cure, Lost Coast Plant Therapy
DIY: Baking soda solution (1 tbsp per gallon of water with few drops of dish soap)

Prevention

Improve air circulation in grow area
Maintain humidity below 60%
Avoid wetting leaves during watering
Remove affected leaves promptly
Use silica supplements to strengthen plants
Consider using powdery mildew resistant strains

Botrytis (Bud Rot)

Severe

Symptoms

Gray/brown fuzzy mould inside buds
Buds turn brown and wilt
Initial signs: fan leaves attached to buds wither and die
White mycelium inside infected buds
Musty, mouldy smell

Treatment

Removal: Immediately remove and destroy all infected buds
Organic: Increase airflow and reduce humidity
Commercial: Preventative fungicides (limited effectiveness once infection starts)
IMPORTANT: Do not consume infected material - discard completely

Prevention

Maintain humidity below 50% during flowering
Ensure excellent air circulation around buds
Defoliate strategically to improve airflow
Avoid dense, tightly packed buds in high humidity climates
Consider genetics with open bud structure for humid regions
Preventative sprays before bud formation

Tobacco Mosaic Virus

Moderate

Symptoms

Mottled green-yellow pattern on leaves
Twisted, distorted leaf growth
Stunted growth and reduced yields
Yellow or light green spots/streaks
Symptoms may appear similar to nutrient issues

Treatment

No cure available: Remove and destroy infected plants
Quarantine: Separate affected plants immediately
Disinfect: Clean all tools, pots, and surfaces with 10% bleach solution
Prevention: Only viable approach once identified

Prevention

Wash hands before handling plants
Don't smoke or handle tobacco near cannabis plants
Disinfect tools between plants
Use clean, new growing medium
Quarantine new plants for observation
Remove weeds that might harbour the virus

Environmental Controls

Climate Control: Maintain optimal temperature (18-27°C/65-80°F) and humidity (40-60% veg, 40-50% flower)
Air Circulation: Use oscillating fans to create gentle air movement across all plant surfaces
Filtration: HEPA filtration on intake air can reduce spores and pest entry
Light Management: Proper light cycle management reduces stress and susceptibility
Clean Water: Use filtered water free of contaminants and pathogens

Sanitation Practices

Clean Entry: Implement a clean entry protocol (wash hands, change clothes)
Tool Sterilisation: Disinfect tools with 70% isopropyl alcohol between plants
Remove Debris: Clear dead leaves and plant material regularly
Clean Grow Space: Regular cleaning of all surfaces with hydrogen peroxide solution
Foot Baths: Use disinfectant foot baths at entry points to larger grow operations
Clean Containers: Sterilise pots and trays between grow cycles

Organic Treatment Options

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Treatment	Effective Against	Application Method	Safety Considerations
Neem Oil	Spider mites, aphids, whiteflies, powdery mildew (early stages)	Mix 5ml neem oil with 1L water + few drops of dish soap. Spray completely, focusing on leaf undersides. Repeat every 5-7 days.	Not for late flowering (affects taste). Apply in evening to prevent leaf burn. Stop 2-3 weeks before harvest.
Insecticidal Soap	Soft-bodied insects (aphids, mites, thrips, whiteflies)	Use commercial product or mix 1 tbsp mild liquid soap in 1L water. Spray directly on pests. Repeat every 3-4 days.	Test on small area first. Some plants may be sensitive. No systemic action - must contact insects directly.

DIY Treatment Recipes

All-Purpose Insect Spray

Ingredients:

1 tbsp cold-pressed neem oil
1 tsp liquid castile soap
1 L water
Optional: 10 drops essential oil (rosemary, peppermint, or citrus)

Instructions:

Mix soap in water first until dissolved
Slowly add neem oil while continuing to mix
Add essential oils if using
Transfer to spray bottle and shake well before each use
Apply in evening, covering all plant surfaces including leaf undersides
Reapply every 5-7 days for 3-4 applications

Effective against: Spider mites, aphids, thrips, whiteflies, and other soft-bodied insects

Important Treatment Warnings

Never Apply During Light Cycle

Always apply foliar treatments when lights are off to prevent leaf burn. Ideally, apply at dusk or just before lights out.

Stop All Treatments Before Harvest

Discontinue all treatments at least 2 weeks before harvest (longer for some treatments). Follow product guidelines for specific timelines.

Need personalized advice on treatments? Chat with our AI Herbal Advisor for custom guidance based on your specific situation.