Contents
Common Insect Pests
Aphids
| Characteristic | Description |
|---|
| Appearance | Small (1-3mm), pear-shaped, various colors (green, black, white) |
| Signs | Clusters on new growth and undersides of leaves |
| Damage | Stunted growth, curled leaves, sticky honeydew secretions |
| Life Cycle | 7-10 days, reproduce rapidly, both sexual and asexual reproduction |
| Organic Control | Insecticidal soap, neem oil, ladybugs, lacewings |
| Chemical Control | Pyrethrins, imidacloprid (not for flowering plants) |
| Prevention | Regular inspection, yellow sticky traps, healthy plants |
Fungus Gnats
| Characteristic | Description |
|---|
| Appearance | Small (2-4mm) black flies, larvae are white/translucent with black heads |
| Signs | Adults flying around soil surface, larvae in top 2-3 inches of medium |
| Damage | Root damage from larvae, stunted growth, wilting |
| Life Cycle | 17-28 days, egg to adult in warm conditions |
| Organic Control | Sticky traps, Bacillus thuringiensis (BTI), nematodes |
| Chemical Control | IGRs (insect growth regulators), soil drenches |
| Prevention | Avoid overwatering, top-dress with dry sand or diatomaceous earth |
Thrips
| Characteristic | Description |
|---|
| Appearance | Tiny (0.5-2mm), slender insects with fringed wings, various colors |
| Signs | Silver/bronze streaking on leaves, black fecal specks |
| Damage | Stippled leaves, distorted growth, potential virus transmission |
| Life Cycle | 2-3 weeks, eggs laid inside leaf tissue |
| Organic Control | Insecticidal soap, neem oil, predatory mites (Amblyseius) |
| Chemical Control | Spinosad, abamectin |
| Prevention | Blue sticky traps, screen vents/openings, clean growing area |
Whiteflies
| Characteristic | Description |
|---|
| Appearance | Tiny (1-2mm) white moth-like insects |
| Signs | Flies up when plants are disturbed, congregates on leaf undersides |
| Damage | Chlorotic spots, honeydew secretion, sooty mold, weakened plants |
| Life Cycle | 3-4 weeks, can continue year-round indoors |
| Organic Control | Yellow sticky traps, insecticidal soap, neem oil, Encarsia formosa (parasitic wasp) |
| Chemical Control | Pyrethrins, imidacloprid (vegetative only) |
| Prevention | Regular inspection, sticky traps, companion plants (marigolds) |
Caterpillars (Budworms)
| Characteristic | Description |
|---|
| Appearance | Vary in size (1-5cm), often green/brown with stripes |
| Signs | Holes in leaves/buds, frass (droppings), visible caterpillars |
| Damage | Consumed leaves, hollowed buds, potential bud rot from waste |
| Life Cycle | Egg to adult in 1-2 months, seasonal outdoors |
| Organic Control | Bacillus thuringiensis (BT), spinosad, hand removal |
| Chemical Control | Various insecticides (avoid on flowering plants) |
| Prevention | Physical barriers, row covers, regular inspection |
Mites and Microscopic Pests
Spider Mites
| Characteristic | Description |
|---|
| Appearance | Tiny (0.3-0.5mm) spider-like pests, various colors |
| Signs | Fine webbing, stippled leaves (tiny yellow/white spots) |
| Damage | Chlorotic leaves, reduced photosynthesis, plant death in severe cases |
| Life Cycle | 7-14 days (faster in warm, dry conditions) |
| Organic Control | Predatory mites, insecticidal soap, neem oil |
| Chemical Control | Abamectin, bifenazate, spiromesifen |
| Prevention | Maintain humidity 50-60%, regular inspection with magnifier, quarantine new plants |
Broad Mites
| Characteristic | Description |
|---|
| Appearance | Microscopic (0.1-0.2mm), translucent/white |
| Signs | Twisted new growth, shiny curled leaves, stunted growth |
| Damage | Severe distortion of new growth, bronzing of tissue |
| Life Cycle | 4-7 days, extremely rapid reproduction |
| Organic Control | Predatory mites (A. swirskii), sulfur applications |
| Chemical Control | Abamectin, spiromesifen |
| Prevention | Strict quarantine, dips for new plants, maintaining cleanliness |
Russet Mites
| Characteristic | Description |
|---|
| Appearance | Microscopic (0.1-0.2mm), carrot/wedge-shaped |
| Signs | Upward leaf curling, bronzing from bottom up, plant looks stressed |
| Damage | Reduced vigor, brittle stems, nutrient deficiency-like symptoms |
| Life Cycle | 7-10 days, multiple generations simultaneously |
| Organic Control | Sulfur applications, neem oil with persistence |
| Chemical Control | Abamectin, spiromesifen, oils with persistence |
| Prevention | Regular inspection with 60x+ magnification, dips for new plants |
Root Aphids
| Characteristic | Description |
|---|
| Appearance | Small (1-2mm), pear-shaped, white to light brown |
| Signs | Slow decline, sometimes white waxy substance on soil/roots |
| Damage | Stunted growth, nutrient deficiencies, wilting |
| Life Cycle | Complex with winged and non-winged forms, soil-persistent |
| Organic Control | Beneficial nematodes, neem soil drench |
| Chemical Control | Imidacloprid soil drench (vegetative only) |
| Prevention | Sterile growing media, avoid overwatering, root zone barriers |
Fungal Diseases
Powdery Mildew
| Characteristic | Description |
|---|
| Appearance | White, powdery patches on leaves, stems, sometimes buds |
| Signs | Initially small round spots that expand and coalesce |
| Damage | Reduced photosynthesis, stunted growth, reduced yield |
| Life Cycle | 3-7 days from infection to new spore production, airborne spread |
| Organic Control | Potassium bicarbonate, neem oil, milk solution (40% milk:water) |
| Chemical Control | Sulfur, myclobutanil (vegetative only), various fungicides |
| Prevention | Good air circulation, avoid high humidity, resistant varieties |
Botrytis (Bud Rot)
| Characteristic | Description |
|---|
| Appearance | Gray/brown fuzzy mold, usually starting inside dense buds |
| Signs | Brown/wilted bud leaves, internal gray fuzzy growth, musty smell |
| Damage | Destroyed flower clusters, potential mycotoxin production |
| Life Cycle | Fast-spreading in humid conditions, especially 65%+ humidity |
| Organic Control | Remove infected buds immediately, increase airflow |
| Chemical Control | Limited options during flowering, preventative biofungicides |
| Prevention | Maintain humidity <50% during flowering, proper spacing, defoliation |
Fusarium
| Characteristic | Description |
|---|
| Appearance | Wilting despite adequate water, stem discoloration |
| Signs | Brown streaking inside stems, root rot, plant collapse |
| Damage | Root/stem rot, vascular wilt, plant death |
| Life Cycle | Soil-persistent for years, spreads through water and tools |
| Organic Control | Limited, remove infected plants entirely |
| Chemical Control | Limited, mostly preventative treatments |
| Prevention | Sterile growing media, clean tools, resistant varieties |
Pythium (Root Rot)
| Characteristic | Description |
|---|
| Appearance | Brown slimy roots, stunted growth, wilting |
| Signs | Plants that don’t uptake water properly, brown root tissue |
| Damage | Root decay, nutrient deficiencies, stunting, death |
| Life Cycle | Favors wet conditions, spreads through water |
| Organic Control | Beneficial bacteria, hydrogen peroxide drench |
| Chemical Control | Mefenoxam, propamocarb (preventative) |
| Prevention | Avoid overwatering, ensure proper drainage, clean system |
Leaf Septoria (Yellow Leaf Spot)
| Characteristic | Description |
|---|
| Appearance | Small yellow spots with dark brown borders |
| Signs | Begins on lower leaves, progresses upward |
| Damage | Reduced photosynthesis, premature leaf drop |
| Life Cycle | Spreads through water splash, can overwinter in debris |
| Organic Control | Copper fungicides, potassium bicarbonate |
| Chemical Control | Chlorothalonil, azoxystrobin (vegetative only) |
| Prevention | Avoid overhead watering, remove affected leaves |
Bacterial & Viral Issues
Bacterial Leaf Spot
| Characteristic | Description |
|---|
| Appearance | Water-soaked dark spots with yellow halos |
| Signs | Spots that enlarge and may develop black/necrotic centers |
| Damage | Leaf damage, potential systemic infection |
| Life Cycle | Spreads through water and physical contact |
| Organic Control | Copper-based products, remove infected tissue |
| Chemical Control | Limited options, streptomycin rarely used |
| Prevention | Avoid overhead watering, space plants properly |
Tobacco Mosaic Virus (TMV)
| Characteristic | Description |
|---|
| Appearance | Mottled light/dark pattern on leaves, sometimes distortion |
| Signs | Mosaic pattern, stunted or malformed growth |
| Damage | Reduced growth and yield, not typically fatal |
| Life Cycle | Extremely stable, spreads through handling and tools |
| Organic Control | None effective, remove infected plants |
| Chemical Control | None available |
| Prevention | Wash hands, sterilize tools, don’t handle tobacco before plants |
Hop Latent Viroid (HLVd)
| Characteristic | Description |
|---|
| Appearance | Stunted growth, brittle stems, reduced trichomes |
| Signs | “Dudding” - poor branching, reduced potency |
| Damage | Reduced yield (30-50%), lower cannabinoid/terpene content |
| Life Cycle | Infectious RNA, spreads through contact and tools |
| Organic Control | None effective, remove infected plants |
| Chemical Control | None available |
| Prevention | Test mother plants, sterilize tools (10% bleach or 70% alcohol) |
Physiological Disorders
Nutrient Deficiencies vs. Pest Damage
| Issue | Key Distinguishing Features |
|---|
| Nitrogen Deficiency | Even yellowing starting with lower leaves, no spots or stippling |
| Spider Mite Damage | Speckling/stippling effect, webbing present, visible mites under magnification |
| Magnesium Deficiency | Interveinal yellowing with green veins, no distortion |
| Broad Mite Damage | Twisted new growth, shiny leaves, symptoms concentrated at growth tips |
| Calcium Deficiency | New leaves hooked, distorted, sometimes necrotic spots |
| Russet Mite Damage | Upward leaf curl, progression from bottom up, bronzing |
| Phosphorus Deficiency | Dark green leaves with purple stems, even pattern |
| Thrips Damage | Silver streaking, black specks (frass), uneven damage |
Environmental Stress Symptoms
| Stress | Symptoms | Often Confused With | Remedy |
|---|
| Heat Stress | Upward leaf curl, brown leaf edges | Russet mites | Lower temperatures, improve airflow |
| Light Burn | Yellow/brown top leaves, bleaching | Nutrient deficiency | Increase light distance, lower intensity |
| Root Binding | Stunted growth, nutrient issues | Pest infestation | Transplant to larger container |
| pH Imbalance | Nutrient lockout symptoms, mottling | Multiple deficiencies | Correct pH, flush if necessary |
| Over/Under Watering | Drooping/wilting, yellow leaves | Root disease | Adjust watering schedule |
| Wind Burn | Leaf curl, brown edges, twisted growth | Broad mites | Reduce fan intensity, redirect airflow |
Integrated Pest Management
Preventative Applications Schedule
| Product | Application Rate | Frequency | Target Pests | Application Notes |
|---|
| Insecticidal Soap | 2-3 tbsp/gallon | Weekly | Soft-bodied insects | Good coverage of undersides, no residual |
| Neem Oil | 2-5 ml/liter | 7-10 days | Multiple pests | Apply in evening, covers both surfaces |
| Beneficial Bacteria | Label rate | 2-4 weeks | Soil pathogens | Soil drench, root applications |
| Silica | Product-specific | Weekly | Strengthens plants | Foliar or root application |
| Predatory Mites | 1000/100 sq ft | Every 2-4 weeks | Spider mites, thrips | Preventative release |
| Mycorrhizae | Label rate | At transplant | Root health | Direct root contact |
Beneficial Insects Guide
| Beneficial | Target Pest | Release Rate | Conditions Required | Effectiveness Timeline |
|---|
| Predatory Mites | Spider mites, broad mites, thrips | 2-10/plant | 60-80% humidity, 65-85°F | 2-3 weeks |
| Lady Beetles | Aphids, small insects | 2-4/plant | Not too hot, nectar sources | Immediate but may fly away |
| Lacewings | Aphids, thrips, small larvae | 1-3 eggs/plant | Flowers for adults | 1-2 weeks after hatch |
| Parasitic Wasps | Whiteflies, aphids | 1 card/20 sq ft | Nectar sources, moderate temps | 2-3 weeks |
| Beneficial Nematodes | Soil pests, fungus gnats | Soil drench | Moist soil, 55-85°F | 2-5 days |
| Rove Beetles | Fungus gnats, soil pests | 1 per sq ft | Moist environment | 3-4 weeks |
Rotation Plan for Pest Management
Proper rotation prevents resistance development. Use products with different modes of action.
| Week | Foliar Treatment | Root Zone Treatment | Mode of Action |
|---|
| 1 | Insecticidal soap | Beneficial bacteria | Physical, biological |
| 2 | Essential oils (rosemary, etc.) | Mycorrhizae boost | Biochemical |
| 3 | Bacillus thuringiensis (BT) | Beneficial nematodes | Biological |
| 4 | Potassium bicarbonate + silica | Trichoderma fungi | Physical, biological |
| 5 | Start rotation again | | |
Important: Always check regulations for approved products in your region. Cannabis cultivation may have specific restrictions on pesticide use, especially for commercial production.
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