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Accurate pest identification is the foundation of effective management. Treating for the wrong pest wastes time, money, and can worsen the problem by killing beneficial organisms. This guide covers the most common cannabis pests with diagnostic criteria, life cycle information, and evidence-based treatment protocols.
Key Principle: Always confirm pest identity before applying any treatment. Use a jeweler's loupe (30x minimum) or USB microscope. Many pest symptoms overlap with nutrient deficiencies and environmental stress.
The most destructive cannabis pest worldwide. Spider mites can reduce yields by 70-100% if left unchecked.
| Attribute |
Detail |
| Taxonomy |
Arachnida (not insects); related to spiders and ticks |
| Size |
0.4-0.5mm adult females; barely visible to naked eye |
| Color |
Two-spotted spider mites: pale green to yellow with two dark spots; red spider mites: reddish-brown |
| Location |
Undersides of leaves; along leaf veins; between bud sites in late infestations |
| Key Sign |
Fine silk webbing between leaves and calyxes (advanced infestations) |
| Stage |
Symptom |
| Early |
Tiny white or yellow stippling (pinprick dots) on upper leaf surface |
| Moderate |
Leaves appear bronzed or bleached; stippling coalesces into larger patches |
| Advanced |
Fine webbing visible; leaves curl, dry, and drop; bud contamination |
| Phase |
Duration (at 77°F / 25°C) |
| Egg to adult |
5-7 days |
| Adult lifespan |
2-4 weeks |
| Eggs per female |
50-100 |
| Generations per year |
12-20 (indoor, year-round) |
Critical: At 80°F (27°C) and low humidity, spider mite reproduction rate doubles. A single female can produce thousands of descendants in three weeks.
| Method |
Agent |
Application Rate |
Timing |
Notes |
| Biological |
Phytoseiulus persimilis (predatory mite) |
2-5 per plant (light); 10+ per plant (heavy) |
Any stage |
Most effective at 60-80% RH; does not survive below 50% RH |
| Biological |
Neoseiulus californicus |
1-2 per plant |
Preventive |
Tolerates lower humidity than P. persimilis; slower acting |
| Organic |
Neem oil (azadirachtin 0.3-1.0%) |
2-5 mL/L water |
Vegetative only |
Disrupts molting and feeding; avoid in flower |
| Organic |
Rosemary oil (Essentria IC3) |
Per label rate |
Any stage (avoid buds) |
Contact killer; short residual |
| Organic |
Insecticidal soap (potassium salts of fatty acids) |
20-30 mL/L water |
Any stage (avoid buds) |
Contact kill only; must coat the pest |
| Chemical |
Abamectin (Avid) |
Per label rate |
Vegetative only |
Systemic; 21-day minimum harvest interval; rotate mode of action |
| Physical |
Diatomaceous earth |
Dust on soil surface |
Any stage |
Physical abrasion; loses efficacy when wet |
- Maintain 55-65% RH during vegetative stage (spider mites prefer <50% RH)
- Quarantine all clones for 14 days; inspect undersides with 30x loupe
- Introduce predatory mites prophylactically at 0.5-1 per plant
- Avoid excess nitrogen, which produces soft growth favored by mites
¶ Thrips (Frankliniella occidentalis, Thrips tabaci, and others)
Second most common cannabis pest. Thrips are difficult to control because they hide inside leaf tissue and pupate in the soil.
| Attribute |
Detail |
| Taxonomy |
Thysanoptera; elongated, fringed-wing insects |
| Size |
1-2mm adults; 0.5mm larvae |
| Color |
Adults: yellow, brown, or black; Larvae: pale yellow to white |
| Location |
Leaf undersides; inside leaf folds; on flowers in late infestations |
| Key Sign |
Black fecal specks on silvered leaf surfaces |
| Stage |
Symptom |
| Early |
Silvery or bronze speckling on leaves; distorted new growth |
| Moderate |
Leaves develop necrotic patches; leaf edges curl upward |
| Advanced |
Black fecal dots visible; stunted growth; bud scarring and discoloration |
| Phase |
Duration (at 72°F / 22°C) |
| Egg (in leaf tissue) |
4-7 days |
| Larva (2 instars) |
8-10 days |
| Pupa (in soil) |
4-7 days |
| Adult |
30-45 days |
Note: Eggs are inserted into leaf tissue with an ovipositor, making them unreachable by foliar sprays. This is why multi-treatment cycles are essential.
| Method |
Agent |
Application Rate |
Timing |
Notes |
| Biological |
Neoseiulus cucumeris (predatory mite) |
25-50 per m² |
Preventive and light infestations |
Broadcast on foliage; establish before thrips arrive |
| Biological |
Orius insidiosus (minute pirate bug) |
1-2 per plant |
Moderate to heavy infestations |
Most aggressive thrips predator; needs pollen to colonize |
| Biological |
Stratiolaelaps scimitus (soil mite) |
25-50 per m² to soil |
Targets soil pupae |
Apply to top 2 inches of medium |
| Organic |
Spinosad |
Per label rate |
Vegetative only |
Most effective organic thrips control; 7-day harvest interval |
| Organic |
Blue or yellow sticky traps |
1 trap per 4-8 plants |
Monitoring and adult reduction |
Blue attracts thrips; yellow also catches fungus gnats and whiteflies |
| Chemical |
Cyantraniliprole (Mainspring) |
Per label rate |
Vegetative only |
Systemic; group 28 IRAC; rotate modes of action |
- Install insect screens (0.2mm mesh) on all air intents
- Avoid bringing cut flowers or outdoor plants near the grow space
- Use blue sticky cards for early detection
- Maintain 60-70% RH (thrips prefer drier conditions)
Most common soil-dwelling pest. Fungus gnat larvae feed on roots and organic matter in the growing medium.
| Attribute |
Detail |
| Taxonomy |
Diptera (true flies); Sciaridae family |
| Size |
Adults: 2-4mm; Larvae: 5-7mm |
| Color |
Adults: dark gray to black; Larvae: translucent white with glossy black head |
| Location |
Adults on soil surface and lower leaves; larvae in top 2-3 inches of medium |
| Key Sign |
Weak, erratic flight around soil surface; larvae visible when medium is disturbed |
| Stage |
Symptom |
| Seedling/Clone |
Severe root feeding; plant death; total tray loss |
| Vegetative |
Slowed growth; yellowing lower leaves; minor root damage |
| Flowering |
Reduced nutrient uptake; minor yield loss; vector for root pathogens |
Note: Adults do not damage plants. Larvae cause root feeding, which is most destructive to seedlings and young plants. Mature plants tolerate moderate gnat pressure with minimal yield impact.
| Phase |
Duration (at 72°F / 22°C) |
| Egg |
4-6 days |
| Larva (4 instars) |
12-14 days |
| Pupa |
4-5 days |
| Adult |
7-10 days |
| Method |
Agent |
Application Rate |
Timing |
Notes |
| Biological |
Steinernema feltiae (beneficial nematodes) |
1 million per 200 sq ft |
Any stage |
Soil drench; water before and after application; kills larvae and pupae |
| Biological |
Stratiolaelaps scimitus (soil mite, formerly Hypoaspis miles) |
25-50 per m² |
Any stage |
Lives in top 2 inches of medium; eats larvae and pupae |
| Biological |
Bacillus thuringiensis israelensis (BTi / Gnatrol) |
0.5-1 g/L water |
Any stage |
Water drench; targets larvae specifically; repeat 3-4 times at 3-day intervals |
| Organic |
Yellow sticky traps |
1 trap per 4 plants |
Monitoring and adult reduction |
Place at soil level; replace weekly |
| Organic |
Hydrogen peroxide (3%) drench |
1 part 3% H2O2 to 4 parts water |
Any stage |
Kills larvae on contact; also oxygenates roots |
| Cultural |
Dry top layer |
Let top 1-2 inches dry between waterings |
Prevention |
Eliminates egg-laying habitat; simplest and most effective prevention |
- Allow top 1-2 inches of growing medium to dry between waterings
- Use well-draining medium; avoid waterlogged conditions
- Apply sticky traps at soil level from seedling stage
- Avoid overwatering; fungus gnats thrive in consistently wet medium
¶ Aphids (Myzus persicae, Macrosiphum euphorbiae, and others)
Rapid-reproducing sap-sucking insects that colonize new growth and undersides of leaves.
| Attribute |
Detail |
| Taxonomy |
Hemiptera (true bugs); Aphididae family |
| Size |
2-4mm adults |
| Color |
Green, black, pink, yellow, or white; some species are winged |
| Location |
Clusters on new growth, leaf undersides, and stem tips |
| Key Sign |
Sticky honeydew residue on leaves; sooty mold growing on honeydew; ants farming aphids |
| Stage |
Symptom |
| Early |
Small clusters on new growth; slight leaf curling |
| Moderate |
Severe leaf curling and distortion; honeydew coating on lower leaves; sooty mold |
| Advanced |
Stunted growth; bud contamination; virus transmission (CMV, Cucumber Mosaic Virus) |
| Phase |
Detail |
| Reproduction |
Parthenogenetic (females produce live clones without mating) |
| Generation time |
7-10 days at 72°F (22°C) |
| Offspring per female |
40-80 live young |
| Annual generations |
20-30+ |
| Method |
Agent |
Application Rate |
Timing |
Notes |
| Biological |
Ladybugs (Coccinella septempunctata) |
1,500+ per 4x4 area |
Any stage |
Release at dusk; mist plants first to encourage them to stay |
| Biological |
Green lacewings (Chrysoperla carnea) |
1,000-2,000 eggs per 4x4 |
Any stage |
Larvae are aggressive aphid predators ("aphid lions") |
| Biological |
Aphidius colemani (parasitic wasp) |
0.5-1 per m² |
Preventive to light |
Parasitizes aphids; produces characteristic "mummies" |
| Organic |
Insecticidal soap |
20-30 mL/L water |
Any stage (avoid buds) |
Must contact the aphid; repeat every 2-3 days |
| Organic |
Neem oil |
2-5 mL/L water |
Vegetative only |
Repellent and growth regulator |
| Physical |
Water spray |
Strong stream (outdoor only) |
Any stage |
Physically removes aphids; repeat every 2-3 days |
- Inspect new clones daily for the first 2 weeks
- Avoid excess nitrogen, which produces soft growth favored by aphids
- Release ladybugs or lacewings as a preventive measure
- Monitor for ants, which farm and protect aphids from natural predators
Small white flying insects that feed on plant sap from leaf undersides.
| Attribute |
Detail |
| Taxonomy |
Hemiptera; Aleyrodidae family |
| Size |
1-2mm adults |
| Color |
Adults: white, moth-like; Eggs: pale yellow; Nymphs: translucent to pale green |
| Location |
Undersides of leaves; fly up when foliage is disturbed |
| Key Sign |
Cloud of white insects when leaves are shaken; honeydew and sooty mold |
| Stage |
Symptom |
| Early |
Pale yellow spots on leaves; adults visible when plant is disturbed |
| Moderate |
Generalized yellowing; sticky honeydew; sooty mold on lower leaves |
| Advanced |
Leaf drop; stunted growth; reduced vigor; virus transmission |
| Phase |
Duration (at 72°F / 22°C) |
| Egg |
5-7 days |
| Nymph (4 instars) |
15-20 days |
| Pupa |
5-7 days |
| Adult |
10-18 days |
| Method |
Agent |
Application Rate |
Timing |
Notes |
| Biological |
Encarsia formosa (parasitic wasp) |
1-2 per plant |
Any stage |
Parasitizes whitefly nymphs; releases tiny wasps (do not sting humans) |
| Biological |
Eretmocerus eremicus |
1-2 per plant |
Moderate to heavy |
More effective than E. formosa at higher temperatures |
| Organic |
Yellow sticky traps |
1 per 4-8 plants |
Monitoring and adult reduction |
Whiteflies strongly attracted to yellow |
| Organic |
Insecticidal soap |
20-30 mL/L water |
Any stage (avoid buds) |
Contact kill; must coat nymphs and adults |
| Organic |
Neem oil |
2-5 mL/L water |
Vegetative only |
Growth regulator; disrupts molting |
Chewing insects that consume leaf tissue and bore into flowers.
| Attribute |
Detail |
| Taxonomy |
Lepidoptera (moths and butterflies); larval stage |
| Size |
1-50mm depending on species |
| Color |
Green, brown, striped, or mottled; often matches foliage |
| Location |
On leaves (chewing holes); inside buds (bore holes with frass) |
| Key Sign |
Large irregular holes in leaves; frass (droppings) on leaves; buds with entry holes and internal damage |
| Location |
Symptom |
| Leaves |
Large, irregular holes; entire sections consumed |
| Buds/Flowers |
Entry hole with frass; internal hollowing; bud rot secondary infection |
| Stems |
Bored tunnels; wilting above damage point |
Critical: Caterpillar damage inside buds creates entry points for Botrytis cinerea (bud rot). A single caterpillar can destroy multiple colas in a week.
| Method |
Agent |
Application Rate |
Timing |
Notes |
| Biological |
Bacillus thuringiensis subsp. kurstaki (BTk) |
1-2 g/L water |
Any stage |
Specific to caterpillars; safe for beneficial insects and humans; organic |
| Biological |
Trichogramma wasps |
Release cards weekly |
Preventive |
Parasitize caterpillar eggs before they hatch |
| Physical |
Hand removal |
Inspect nightly |
Outdoor primarily |
Effective for small populations |
| Organic |
Neem oil |
2-5 mL/L water |
Any stage (avoid buds) |
Repels egg-laying moths |
- Install fine mesh barriers around plants
- Inspect plants nightly during peak moth activity (dusk)
- Apply BTk prophylactically every 7-14 days
- Remove and destroy any infested buds immediately
Microscopic mites that cause damage often mistaken for nutrient deficiency or genetic mutation.
| Attribute |
Detail |
| Size |
0.15-0.25mm; invisible to naked eye; requires 60x+ magnification |
| Color |
Translucent to pale yellow; oval-shaped |
| Location |
Newest growth and meristematic tissue (plant growing tips) |
| Key Sign |
New leaves emerge twisted, cupped, or glossy; leaf edges curl downward |
| Stage |
Symptom |
| Early |
New growth appears glossy, waxy, or blistered; leaf edges curl downward |
| Moderate |
Growth tips twist and deform; stems become brittle; buds are stunted |
| Advanced |
Terminal growth dies; plant resembles severe calcium or boron deficiency |
| Method |
Agent |
Application Rate |
Timing |
Notes |
| Biological |
Neoseiulus californicus |
2-5 per plant |
Any stage |
Most effective predatory mite for broad mites |
| Biological |
Amblyseius swirskii |
5-10 per plant |
Any stage |
Aggressive predator; works well at higher temperatures |
| Organic |
Neem oil |
2-5 mL/L water |
Vegetative only |
Contact kill; repeated applications needed |
| Organic |
Insecticidal soap |
20-30 mL/L water |
Any stage |
Contact kill; must reach growing tips |
| Chemical |
Abamectin (Avid) |
Per label rate |
Vegetative only |
Systemic; 21-day minimum harvest interval |
The most elusive cannabis pest. Microscopic eriophyid mites that feed on plant cells.
| Attribute |
Detail |
| Size |
0.15-0.2mm; require 60-100x magnification; carrot-shaped |
| Color |
Pale yellow to cream |
| Location |
Starts on lower leaves; moves upward through the plant |
| Key Sign |
Leaves curl upward at edges ("taco leaves"); stems become brittle and glassy; damage progresses upward from bottom |
| Stage |
Symptom |
| Early |
Lower leaf edges curl upward; stems appear shiny or glassy |
| Moderate |
Curling progresses upward; reduced vigor; fewer trichomes |
| Advanced |
Entire plant stunted; buds are small and lack resin; plant may die |
Warning: Russet mites are frequently misdiagnosed as calcium deficiency, light stress, or genetics. If lower leaves curl upward AND stems are shiny/brittle, suspect russet mites.
| Method |
Agent |
Application Rate |
Timing |
Notes |
| Chemical |
Sulfur burners |
Per label rate |
Vegetative only |
Most effective treatment; never use during flowering |
| Organic |
Neem oil |
2-5 mL/L water |
Vegetative only |
Suppressive, not curative |
| Physical |
Remove and destroy affected tissue |
Prune bottom 1/3 of plant |
Any stage |
Slows spread; does not eliminate |
| Nuclear option |
Destroy entire plant |
Bag and remove from grow space |
Any stage |
If mites reach flowering plants, this may be the only safe option |
| Pest |
Visibility |
Location |
Key Diagnostic |
Speed of Spread |
Primary Treatment |
| Spider Mites |
30x loupe |
Leaf undersides |
Stippling + webbing |
Very fast (days) |
P. persimilis |
| Thrips |
30x loupe |
Leaf surface/folds |
Silvering + black fecal dots |
Fast (days-weeks) |
Spinosad / N. cucumeris |
| Fungus Gnats |
Naked eye |
Soil surface |
Adults flying around pots |
Moderate (weeks) |
BTi + nematodes |
| Aphids |
Naked eye |
New growth |
Clusters + honeydew |
Very fast (days) |
Ladybugs / lacewings |
| Whiteflies |
Naked eye |
Leaf undersides |
White cloud when disturbed |
Moderate (weeks) |
E. formosa / sticky traps |
| Caterpillars |
Naked eye |
Leaves and buds |
Chewing holes + frass |
Variable |
BTk |
| Broad Mites |
60x+ microscope |
Growing tips |
Glossy, twisted new growth |
Fast (days) |
N. californicus |
| Russet Mites |
60-100x microscope |
Lower leaves upward |
Upward leaf curl + glassy stems |
Moderate (weeks) |
Sulfur (veg) / destroy plant |
See Also: /cultivation/pests-diseases | /cultivation/disease-identification | /cultivation/troubleshooting | /cultivation/indoor/grow-guide | /cultivation/outdoor/grow-guide