DISCLAIMER: Cannabis cultivation is illegal in many jurisdictions. This content is provided for educational purposes only. Always research and comply with your local laws and regulations before cultivating cannabis. Unauthorized cultivation may result in legal penalties.
¶ Pest & Disease Management
Pest and disease management is an inevitable part of cannabis cultivation. Whether growing indoors, outdoors, or in a greenhouse, plants face threats from insects, fungi, bacteria, and viruses. An Integrated Pest Management (IPM) approach -- combining prevention, monitoring, biological controls, and targeted treatments -- is the most effective and sustainable strategy.
Detailed Identification: For comprehensive pest identification with life cycles and treatment protocols, see Pest Identification. For fungal, bacterial, and viral diseases with pathology and diagnostic criteria, see Disease Identification. For a complete diagnostic guide to all grow problems, see Troubleshooting Guide.
Golden Rule: Prevention is always easier, cheaper, and safer than treatment. A robust IPM program prevents problems before they start.
¶ Integrated Pest Management (IPM)
IPM is a systematic approach that prioritizes prevention and uses the least invasive control methods first.
¶ IPM Hierarchy
1. PREVENT -- Create an environment hostile to pests and diseases
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2. MONITOR -- Inspect regularly; catch problems early
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3. IDENTIFY -- Correct identification is essential for proper treatment
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4. BIOLOGICAL CONTROL -- Introduce beneficial insects and microorganisms
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5. CULTURAL CONTROL -- Remove affected tissue; improve conditions
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6. ORGANIC TREATMENT -- Neem oil, BT, diatomaceous earth, etc.
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7. CHEMICAL TREATMENT -- Last resort; observe harvest intervals
¶ Prevention Strategies
| Prevention Measure | Implementation | Effectiveness |
|---|---|---|
| Clean grow space | Sanitize tent/room between cycles with hydrogen peroxide or bleach solution | High |
| Inspect new plants | Quarantine clones, new plants, and soil for 7-14 days before introducing to grow space | Critical |
| Positive air pressure | Slightly more intake than exhaust; prevents unfiltered air from entering through gaps | Moderate-High |
| Air filtration | HEPA filter on intake air; reduces spore and pest entry | Moderate |
| Proper clothing | Change clothes before entering grow; don't introduce outdoor pests | Moderate |
| Beneficial insects | Prophylactic release of predatory mites and ladybugs | High (preventive) |
| Optimal VPD | Correct temperature/humidity reduces disease pressure | High |
| Healthy plants | Proper nutrition and environment create natural resistance | Foundational |
| Remove dead material | Clear dead leaves and debris; eliminate pest habitat | Moderate |
¶ Common Cannabis Pests
¶ Spider Mites
The most common and destructive cannabis pest.
| Attribute | Detail |
|---|---|
| Appearance | Tiny (0.5mm); red, brown, or pale; visible as moving dots on leaf undersides |
| Damage Signs | White/yellow stippling on leaves; fine webbing between leaves and buds; leaf drop |
| Conditions Favoring | Warm (75-85°F); dry (30-50% RH); poor airflow |
| Reproduction | Extremely rapid; 50-100 eggs per female; 7-day life cycle |
Treatment Options:
| Treatment | Application | Notes |
|---|---|---|
| Neem oil | Foliar spray (veg only, not flower) | Repels and disrupts life cycle |
| Predatory mites (Phytoseiulus persimilis) | Release on affected plants | Most effective biological control |
| Insecticidal soap | Foliar spray | Contact kill; repeat every 3-5 days |
| Diatomaceous earth | Dust on soil and around base | Physical damage to crawling mites |
| Rosemary oil / Essentria | Foliar spray | Organic contact killer |
| Avid / Abamectin | Chemical (veg only) | Systemic; never use during flowering |
Critical: Spider mites can destroy an entire crop in 1-2 weeks if unchecked. Inspect leaf undersides with a jeweler's loupe (30x+) every 2-3 days.
¶ Aphids
Soft-bodied insects that cluster on new growth and undersides of leaves.
| Attribute | Detail |
|---|---|
| Appearance | Small (2-4mm); green, black, white, or pink; pear-shaped |
| Damage Signs | Curling, distorted new growth; sticky honeydew residue; sooty mold; ants farming aphids |
| Conditions Favoring | Moderate temperatures; high nitrogen feeding; stressed plants |
| Reproduction | Live birth; clones of themselves; extremely rapid population growth |
Treatment Options:
| Treatment | Application | Notes |
|---|---|---|
| Ladybugs | Release in grow area | Voracious aphid predators |
| Lacewings | Release eggs or larvae | Larvae are aggressive aphid predators |
| Neem oil | Foliar spray (veg only) | Repellent and growth disruptor |
| Insecticidal soap | Thorough foliar spray | Contact kill; must hit the aphids |
| Water spray | Physical removal (outdoor) | Blasts aphids off plants |
¶ Whiteflies
Small white flying insects that feed on plant sap from leaf undersides.
| Attribute | Detail |
|---|---|
| Appearance | 1-2mm; white; moth-like; fly up when leaves are disturbed |
| Damage Signs | Yellowing leaves; sticky honeydew; sooty mold; general weakening |
| Conditions Favoring | Warm, humid conditions; poor air circulation |
| Reproduction | Eggs on leaf undersides; multiple generations overlapping |
Treatment Options:
| Treatment | Application | Notes |
|---|---|---|
| Yellow sticky traps | Hang at canopy level | Monitoring and adult reduction |
| Encarsia formosa (parasitic wasp) | Release cards | Parasitizes whitefly pupae |
| Neem oil | Foliar spray (veg only) | Growth regulator |
| BT (Bacillus thuringiensis) | Soil drench and foliar | Specifically targets larvae |
| Insecticidal soap | Foliar spray | Contact kill of adults and nymphs |
¶ Fungus Gnats
Small flying insects whose larvae live in the growing medium and feed on roots.
| Attribute | Detail | |
|---|---|---|
| Appearance | Adults: 2-4mm; dark; weak fliers; seen on soil surface | Larvae: translucent with black head |
| Damage Signs | Adults flying around pots; slow growth; root damage (especially in seedlings) | |
| Conditions Favoring | Consistently wet growing medium; organic matter | |
| Reproduction | Eggs in top 1-2 inches of medium; 3-4 week life cycle |
Treatment Options:
| Treatment | Application | Notes |
|---|---|---|
| Yellow sticky traps | At soil level | Adults only; monitoring and reduction |
| BTi (Bacillus thuringiensis israelensis) (Gnatrol) | Water drench | Kills larvae; repeat 3-4 times |
| Beneficial nematodes (Steinernema feltiae) | Soil drench | Parasitizes larvae and pupae |
| Hypoaspis mites | Soil application | Predatory mites that eat larvae |
| Hydrogen peroxide drench (3%) | Soil drench | Kills larvae on contact; also oxygenates roots |
| Dry out top layer | Let top 1-2 inches dry between waterings | Prevents egg-laying; simplest prevention |
| Diatomaceous earth | Top dressing | Physical barrier |
¶ Thrips
Tiny, slender insects that rasp leaf surfaces and suck plant juices.
| Attribute | Detail |
|---|---|
| Appearance | 1-2mm; slender; yellow, brown, or black; fast-moving |
| Damage Signs | Silver/bronze speckling on leaves; black fecal dots; distorted new growth |
| Conditions Favoring | Warm, dry conditions; introduction from outdoor plants or cut flowers |
| Reproduction | Eggs inserted into leaf tissue; hard to reach with treatments |
Treatment Options:
| Treatment | Application | Notes |
|---|---|---|
| Blue or yellow sticky traps | At canopy level | Monitoring |
| Predatory mites (Neoseiulus cucumeris) | Broadcast on plants and soil | Effective preventive and control |
| Orius bugs | Release in grow area | Aggressive thrips predator |
| Spinosad | Foliar spray | Organic; effective; not during flowering |
| Neem oil | Foliar spray (veg only) | Repellent |
¶ Caterpillars
Larvae of moths and butterflies that chew holes in leaves and bore into buds.
| Attribute | Detail |
|---|---|
| Appearance | Variable (green, brown, striped); 1-3 inches; obvious chewing damage |
| Damage Signs | Large holes in leaves; frass (droppings) on leaves; buds with entry holes |
| Conditions Favoring | Outdoor growing; proximity to moth habitat |
| Reproduction | Moths lay eggs on leaves; caterpillars emerge and feed |
Treatment Options:
| Treatment | Application | Notes |
|---|---|---|
| BT (Bacillus thuringiensis) | Foliar spray | Specific to caterpillars; safe for beneficials; organic |
| Hand removal | Inspect and remove manually | Effective for small infestations |
| Trichogramma wasps | Release cards | Parasitize caterpillar eggs |
| Neem oil | Foliar spray | Repellent for egg-laying |
¶ Common Cannabis Diseases
¶ Powdery Mildew (PM)
The most common fungal disease in cannabis cultivation.
| Attribute | Detail |
|---|---|
| Appearance | White, powdery spots on leaves (top surface first); spreads to cover entire leaf |
| Damage | Reduced photosynthesis; spread to flowers makes them unsalvageable |
| Conditions Favoring | Moderate temperatures (68-77°F); moderate to high humidity; poor air circulation; day/night humidity swings |
| Transmission | Airborne spores; contaminated tools, clothing, or clones |
Treatment Options:
| Treatment | Application | Notes |
|---|---|---|
| Potassium bicarbonate (MilStop) | Foliar spray | Raises leaf surface pH; kills PM on contact |
| Sulfur | Burners (veg) or dust | Effective; never use sulfur on flowers |
| Neem oil | Foliar spray (veg only) | Preventive; curative early stage |
| Hydrogen peroxide | Foliar spray (3% diluted) | Contact kill; organic |
| Beneficial bacteria (Bacillus amyloliquefaciens) | Foliar/soil | Preventive; colonizes leaf surface |
| Remove affected tissue | Prune and bag infected leaves | Essential; prevents spore spread |
Warning: PM on flowers renders buds unsafe for consumption. If PM reaches the flowers, affected buds should be discarded.
¶ Botrytis (Bud Rot / Gray Mold)
A devastating fungal disease that destroys flowers from the inside out.
| Attribute | Detail |
|---|---|
| Appearance | Brown/mushy sections within buds; gray fuzzy mold; buds that crumble when handled |
| Damage | Complete loss of affected colas; can spread to entire plant |
| Conditions Favoring | High humidity (>55% RH); poor airflow; dense buds; cool temperatures (55-70°F) |
| Transmission | Airborne spores; enters through wounds or dense bud interiors |
Treatment Options:
| Treatment | Application | Notes |
|---|---|---|
| Remove affected buds immediately | Cut 1-2 inches below visible rot; bag and remove from grow space | Most critical step |
| Lower humidity | Reduce to 40-45% RH | Essential preventive measure |
| Increase airflow | Add oscillating fans | Disrupts microclimates |
| Remove from heat | Do not attempt to dry or salvage rotted buds | Spores will spread |
| Trichoderma | Soil drench (preventive) | Beneficial fungus that competes with botrytis |
| No chemical cure | Once bud rot sets in, no spray can fix it | Prevention is everything |
¶ Root Rot (Pythium / Fusarium)
Soil and water-borne pathogens that attack root systems.
| Attribute | Detail |
|---|---|
| Appearance | Brown, slimy roots (healthy roots are white/cream); foul smell; wilting despite wet medium |
| Damage | Roots cannot absorb water or nutrients; plant decline; death |
| Conditions Favoring | Warm water (>72°F / 22°C); low oxygen; overwatering; contaminated systems |
| Transmission | Contaminated water, medium, or tools; systemic in recirculating hydroponic systems |
Treatment Options:
| Treatment | Application | Notes |
|---|---|---|
| Beneficial bacteria (Bacillus amyloliquefaciens / Hydroguard) | Root zone drench | Outcompetes pathogens; best preventive |
| Hydrogen peroxide (3-11% depending on system) | Root drench or reservoir treatment | Kills pathogens and roots; use carefully |
| Lower water temperature | Below 68°F (20°C) | Slows pathogen growth |
| Increase oxygen | More air stones; lower water level in DWC | Roots need oxygen to fight disease |
| Sterilize system (hydroponics) | Full reservoir change; H2O2 clean | Essential for recirculating systems |
| Remove dead roots | Trim affected tissue | Promotes new healthy root growth |
¶ Damping Off
Affects seedlings and young plants; caused by multiple soil-borne pathogens.
| Attribute | Detail |
|---|---|
| Appearance | Seedling stem becomes thin and water-soaked at soil line; plant collapses and dies |
| Damage | Complete seedling death; often affects entire tray |
| Conditions Favoring | Overwatered medium; poor drainage; cool, wet conditions; contaminated soil |
| Transmission | Soil-borne; present in many garden soils |
Prevention:
- Use sterile seed-starting medium
- Do not overwater seedlings
- Provide warmth (heat mat) and good air circulation
- Avoid using garden soil for seedlings
- Apply beneficial mycorrhizae at germination
¶ Pest and Disease Identification Table
| Symptom | Likely Cause | Location | Action Priority |
|---|---|---|---|
| White powder on leaves | Powdery Mildew | Leaves, potentially buds | URGENT -- treat immediately |
| Webbing on undersides of leaves | Spider Mites | Leaf undersides | URGENT -- rapid reproduction |
| Brown mushy buds | Botrytis (Bud Rot) | Flower interiors | URGENT -- remove immediately |
| Brown slimy roots | Root Rot (Pythium) | Root zone | HIGH -- can kill plant quickly |
| Tiny flying insects near soil | Fungus Gnats | Soil surface | Moderate -- annoying but manageable |
| Silver speckling on leaves | Thrips | Leaf surfaces | HIGH -- rapid spread |
| Sticky leaves + sooty mold | Aphids or Whiteflies | Leaf undersides, new growth | HIGH -- rapid reproduction |
| Holes chewed in leaves | Caterpillars | Leaves and buds | Moderate -- inspect and remove |
| Seedling collapse at soil line | Damping Off | Stem base | HIGH -- affects entire tray |
| Yellow stippling on leaves | Spider Mites (early) or Thrips | Leaf surfaces | HIGH -- inspect closely to differentiate |
| Ants on plants | Aphids or Scale (ants farming) | Stems and leaves | Moderate -- treat the farmed pest |
¶ Biological Controls
Beneficial organisms that prey on or parasitize cannabis pests.
| Beneficial Organism | Targets | Application | Notes |
|---|---|---|---|
| Ladybugs | Aphids, soft-bodied insects | Release 1,500+ per 4x4 area | Release at dusk; mist plants first |
| Lacewings | Aphids, thrips, mite eggs | Release eggs or larvae | Larvae are the predators |
| Predatory Mites (P. persimilis) | Spider mites | 2-5 per plant | Best at moderate RH (60%+) |
| Predatory Mites (N. cucumeris) | Thrips, broad mites | Broadcast on foliage and soil | Preventive; establish before pests arrive |
| Orius insidiosus | Thrips | Release in grow area | Effective but needs pollen to establish |
| Encarsia formosa | Whiteflies | Release cards | Parasitic wasp (does not sting humans) |
| Trichogramma | Caterpillar eggs | Release cards | Prevents caterpillars before they hatch |
| Hypoaspis miles | Fungus gnat larvae, thrips pupae | Apply to soil | Lives in top 2 inches of medium |
| Beneficial Nematodes | Fungus gnat larvae | Soil drench | Apply with watering |
| Bacillus amyloliquefaciens | Root rot, powdery mildew | Soil drench or foliar | Colonizes root and leaf surfaces |
| Trichoderma | Root rot, soil-borne diseases | Soil amendment | Beneficial fungus |
¶ Chemical Treatments (Last Resort)
WARNING: Chemical pesticides leave residues that are harmful when inhaled. Never apply chemical treatments during flowering. Observe harvest intervals (the time between last application and harvest) strictly. When in doubt, do not use chemicals on cannabis.
| Chemical | Targets | Harvest Interval | Notes |
|---|---|---|---|
| Pyrethrin | Broad-spectrum insect contact kill | 0-3 days | Derived from chrysanthemum; relatively safe but still a chemical |
| Spinosad | Caterpillars, thrips | 7 days | Organic-derived; relatively safe |
| Imidacloprid | Broad-spectrum | Do not use on cannabis | Systemic; extremely long residual; not safe for consumable flowers |
| Myclobutanil | Powdery mildew | Do not use on cannabis | Produces toxic hydrogen cyanide gas when burned |
| Sulfur | Powdery mildew, mites | 14+ days | Safe if used in veg only; never on flowers |
| Abamectin (Avid) | Spider mites, leafminers | 21+ days | Effective but requires long interval |
¶ Quarantine Procedures
Whenever introducing new genetics (clones, seeds, plants) to an existing grow space:
Quarantine Protocol:
- Isolate -- Keep new plants in a separate room or area for 7-14 days
- Inspect -- Examine with a jeweler's loupe (30x+) under bright light daily
- Treat prophylactically -- Apply neem oil (if in veg) or beneficial insects as a preventive
- Monitor -- Watch for any signs of pests or disease throughout quarantine
- Clear -- Only introduce to the main grow space after 14 days pest-free
- Sterilize -- Clean hands, tools, and clothing after handling quarantined plants
¶ Related Pages
- Indoor Grow Guide -- Complete indoor grow with pest scouting schedules, IPM timeline, and troubleshooting tables
- Outdoor Grow Guide -- Complete outdoor grow with companion planting, beneficial insect release, and organic IPM
- Environmental Control -- Environmental conditions that promote or prevent disease
- Indoor Growing -- Maintaining a clean indoor grow space
- Nutrients & Feeding -- Distinguishing nutrient deficiencies from pest damage
- Outdoor Growing -- Outdoor-specific pest pressure and natural controls
- Harvesting & Drying -- Inspecting buds for mold before harvest
- Curing & Storage -- Detecting mold during curing
See Also: /cultivation/indoor/environment | /cultivation/indoor | /cultivation/nutrients | /cultivation/outdoor | /cultivation/harvest-dry | /cultivation/cure-store