Cannabis Cultivation: Integrated Pest Management and Hydroponic Systems

Lectures 4&5 Study Guide for Quiz 2

Integrated Pest Management (IPM)

A decision-making system that combines multiple pest-management strategies—emphasizing prevention, monitoring, correct identification, decision thresholds, multiple controls, evaluation, and recordkeeping—to manage pest populations while reducing unnecessary risks.

IPM Control Hierarchy

A tiered management framework that prioritizes the lowest-risk effective controls, organized in order from: 1. Prevention, 2. Cultural Controls, 3. Mechanical / Physical Controls, 4. Biological Controls, to 5. Chemical Controls.

Spider Mites

Small foliar arthropod pests characterized by rapid reproduction, hidden populations beneath leaves, leaf stippling, yellowing or bronzing, and fine webbing during severe infestations.

Cannabis Aphids

Sap-feeding insect pests that establish colonies on stems and foliage, leading to distorted leaf growth, reduced plant vigor, secretion of sticky honeydew, and subsequent sooty mold development.

Aphid Cast Skins

White, translucent exoskeletons shed onto leaves and stems by developing aphids during their molting process, serving as a primary visual indicator of an active infestation.

Thrips

Slender, minute insect pests that hide within plant tissues and flowers, causing feeding injury visible as silvery feeding scars, distorted growth, and small black fecal spots.

Fungus Gnats

Pests whose winged adults fly near growing media surfaces and whose larvae reside in damp media, feeding on roots, organic debris, and algae under overly moist conditions.

Sticky Cards

Adhesive monitoring tools used to detect and track population trends over time for airborne insect pests such as fungus gnats, thrips, whiteflies, and winged aphids.

Powdery Mildew

A fungal plant disease recognizable by white powdery patches on foliage that decrease photosynthetic surface area and contaminate cannabis flowers, favored by dense canopies and stagnant air.

Botrytis (Gray Mold)

A destructive fungal pathogen that poses a major threat during the flowering stage, thriving in dense flower clusters, high relative humidity, poor airflow, and wounded or dying plant tissue.

Pythium-type Root Rot

A root and crown disease caused by soilborne or waterborne organisms that leads to root discoloration, wilting, stunting, nutrient-deficiency-like symptoms, and total plant collapse.

Scouting

A regular, systematic, documented, representative, and consistent inspection process evaluating upper leaves, lower leaves, stems, media, root zones, and flowers for early pest detection.

Exclusion (IPM)

Biosecurity and structural strategies designed to stop pests from entering a facility via incoming clones, employee clothing, tools, equipment, growing media, or air intake vents.

Quarantine

The protocol of isolating, inspecting, monitoring, and evaluating incoming plant material (clones) before introducing them into the main crop to ensure they are free of pests and pathogens.

Biological Control

The use of living organisms—such as predatory mites, predatory insects, parasitoids, beneficial nematodes, and microbial biocontrol agents—to suppress pest populations, functioning best as a preventative measure at low pest densities.

Pesticide Resistance

An evolutionary outcome where repeated pesticide use creates selection pressure that eliminates susceptible individuals and allows genetically resistant survivors to reproduce, reducing product efficacy over time.

IPM Decision Cycle

The continuous operational loop of pest management: Prevent $\rightarrow$ Scout $\rightarrow$ Identify $\rightarrow$ Measure $\rightarrow$ Decide $\rightarrow$ Control $\rightarrow$ Evaluate $\rightarrow$ Record $\rightarrow$ Repeat.

Hydroponics

Soilless plant production in which crops receive water, essential mineral nutrients, oxygen, and physical root support without dependence on traditional agricultural soil.

Root Respiration

The cellular process described by $\text{Glucose} + \text{Oxygen} \rightarrow \text{Carbon Dioxide} + \text{Water} + \text{Energy}$, providing the energy root cells require for active mineral uptake, growth, cell division, and maintenance.

Transpiration Stream

The continuous pathway of water driven by water potential and transpiration from Root $\rightarrow$ Xylem $\rightarrow$ Stem $\rightarrow$ Leaves $\rightarrow$ Atmosphere.

Photosynthesis

The light-driven biochemical reaction represented by $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Light} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$, requiring light, carbon dioxide, water, and functional leaf tissues.

Macronutrients (Plant)

Essential elements required by plants in large amounts, consisting of nitrogen ($\text{N}$), phosphorus ($\text{P}$), potassium ($\text{K}$), calcium ($\text{Ca}$), magnesium ($\text{Mg}$), and sulfur ($\text{S}$).

Micronutrients (Plant)

Essential trace elements required by plants in smaller amounts, consisting of iron ($\text{Fe}$), zinc ($\text{Zn}$), manganese ($\text{Mn}$), copper ($\text{Cu}$), boron ($\text{B}$), and molybdenum ($\text{Mo}$).

Deep Water Culture (DWC)

A hydroponic system where plant roots are continuously submerged in an oxygenated nutrient reservoir, requiring active aeration via air pumps and air stones to maintain root health.

Nutrient Film Technique (NFT)

A recirculating hydroponic system wherein a shallow, continuous stream of nutrient solution flows along sloped channels over bare root mats, providing simultaneous hydration, nutrients, and atmospheric oxygen exposure.

Drip System (Hydroponics)

A hydroponic method where nutrient solution is pumped through emitters directly to the base of plants growing in a solid medium that supplies physical support, moisture retention, and air-filled pore spaces.

Ebb and Flow (Flood and Drain)

A hydroponic method based on a cycle of Flood $\rightarrow$ Drain $\rightarrow$ Re-aerate $\rightarrow$ Repeat, flooding the root table with nutrient solution before draining it completely back to the reservoir.

Aeroponics

A soilless growing technique where plant roots hang suspended inside an enclosed air chamber and are periodically misted or sprayed with fine droplets of nutrient solution.

Growing Media (Soilless)

Substrates—such as rockwool, coco-based media, perlite, vermiculite, and expanded clay—chosen to supply root anchorage, water holding capacity, drainage, and adequate air-filled pore space.

pH (Hydroponics)

A measurement of acidity or alkalinity in the nutrient solution that directly governs mineral solubility, chemical reactions, and the availability of ions for root uptake.

Electrical Conductivity (EC)

An electrical measurement that reflects the total concentration of dissolved ionic mineral salts in a nutrient solution, though it does not distinguish individual nutrient concentrations.

Controlled-Environment Agriculture (CEA)

An indoor production approach where environmental parameters—such as light, temperature, relative humidity, $\text{CO}_2$, water, nutrients, and airflow—are closely regulated to maximize plant productivity.

Root Zone Requirements

Water + Nutrients + Oxygen

Too little of any one can affect plant function

Water Pathway in Plants

Root → Xylem → Stem → Leaves → Atmosphere

When should you employ hydroponics?

• Land is limited.

• Water efficiency is important.

• Growing conditions need to be carefully controlled.

• Food needs to be produced in urban or indoor environments

When should you employ soil farming?

• Suitable farmland is available.

• Farmers want a simpler growing system.

• Large outdoor areas are available.

• Crops are well suited to local soil and climate conditions

Cannabis Pest Subcategories

• Anthropoids

• Plant Pathogens

• Other Problems (Weeds, algae, abiotic disorders)

Anthropoids Include:

• Mites

• Aphids

• Thrips

• Whiteflies

• Fungus gnats

• Caterpillars

Integrated Pest Management (IPM) Framework

A comprehensive decision-making strategy prioritizing low-risk preventative controls over reactive chemicals, guided by an 8-stage operational loop: Prevent $\rightarrow$ Scout $\rightarrow$ Identify $\rightarrow$ Measure $\rightarrow$ Decide $\rightarrow$ Control $\rightarrow$ Evaluate $\rightarrow$ Record.

IPM Control Hierarchy

A tiered management framework that prioritizes the lowest-risk effective controls in descending order:

1. Prevention

2. Cultural Controls

3. Mechanical / Physical Controls

4. Biological Controls

5. Chemical Controls

Cannabis Pest Categories

The three primary classifications of crop threats:

• Arthropods: Spider mites, aphids, thrips, whiteflies, fungus gnats, caterpillars

• Plant Pathogens: Fungi, oomycetes, bacteria, viruses/viroids

• Other Problems: Weeds, algae, and abiotic disorders

Spider Mite Visual Symptoms

• Leaf stippling (pale speckled feeding wounds)

• Foliar yellowing or bronzing

• Active colonies clustered on the undersides of leaves

• Fine silk webbing spanning plant tissues during severe infestations

Spider Mite Biological Challenges

• Rapid reproduction rates

• Microscopic body size

• Cryptic populations concealed underneath foliage

• High potential to develop pesticide resistance

Cannabis Aphid Infestation Symptoms

• Dense colonies along stems and leaf undersides

• Stunted, distorted, and curled leaf growth

• Reduced overall plant vigor

• Excretion of sticky honeydew fostering sooty mold growth

• Presence of cast skins (translucent white molted exoskeletons)

Cannabis Aphid Management Protocols

• Rigorous inspection and quarantine of incoming plant material

• Regular canopy monitoring and population tracking

• Physical roguing of heavily infested foliage

• Early introduction of biological control agents

• Application of approved treatments when thresholds warrant

Thrips Feeding Damage Characteristics

• Silvery, irregular feeding scars across foliage

• Distorted vegetative growth

• Visible accumulations of minute black fecal spots

• Direct feeding damage to developing flower structures

Thrips Scouting and Control Challenges

• Extremely minute size

• Cryptic habit of hiding deep inside floral buds and tight plant crevices

• Complex life cycles featuring multiple mobile and immobile stages

• Pupation stages that often occur off the foliage in growing media

Fungus Gnat Life Stage Distinctions

• Adults: Weak-flying small gnats observed hovering directly above growing media surfaces

• Larvae: Substrate-dwelling maggots that feed directly on roots, organic debris, and algae

Fungus Gnat Environmental Management

IPM begins primarily with moisture control: eliminating over-irrigation, drying saturated media surfaces, removing standing puddles, and preventing algae growth.

Powdery Mildew Clinical Signs & Impact

• Superficial white, powdery fungal patches across foliage

• Decreased photosynthetic capacity due to blocked light interception

• Direct contamination, spoilage, and unsellability of mature floral clusters

Powdery Mildew Environmental and Biological Risk Factors

• Susceptible cultivar genetics

• Overly dense plant canopies restricting air movement

• Stagnant airflow combined with favorable humidity microclimates

• Introduction of infected mother plants or clones

Botrytis (Gray Mold) Primary Vulnerability & Risk Factors

• Primary Timing: Major destructive threat during the late flowering stage

• Risk Factors: Dense flower clusters, elevated relative humidity, stagnant air movement, mechanical wounds, and senescing/dead plant tissue

Botrytis Cultural Management Protocols

• Strict facility sanitation

• Careful canopy humidity management

• Increased horizontal and vertical air circulation

• Frequent scouting and prompt excision of infected flower clusters

Pythium-type Root Rot

A soilborne or waterborne oomycete disease causing brown root decay, wilting, stunting, nutrient-deficiency symptoms, and total plant collapse in poorly aerated or waterlogged media.

IPM Scouting and Monitoring Tools

A regular, systematic, documented inspection evaluating upper/lower leaves, media, and roots using hand lenses, digital microscopes, and sticky cards to monitor population trends over time.

Exclusion, Quarantine, and Sanitation

• Exclusion: Physical and biosecurity barriers preventing pest entry via vents, clothing, and gear.

• Quarantine: The isolation and inspection of incoming clones before entering production areas.

• Sanitation: Cultural cleanliness protocols, such as clearing plant debris, algae, and standing water, to eliminate pest reservoirs.

Biological Control in IPM

The intentional release of natural enemies (predatory mites, beneficial nematodes, parasitoids, and microbial agents) to suppress pest populations; operates as a preventative measure that works best at low pest densities.

Pesticide Resistance Mechanism & Management

The evolutionary selection where repeated pesticide applications eliminate susceptible individuals and allow genetically resistant survivors to multiply; managed by using chemicals strictly as a last resort, rotating modes of action, and adhering to legal label requirements.

Photosynthesis vs. Root Respiration

• Photosynthesis: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{Light} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$, creating carbohydrates in leaves.

• Root Respiration: $\text{Glucose} + \text{Oxygen} \rightarrow \text{Carbon Dioxide} + \text{Water} + \text{Energy}$, powering root cell division and active mineral absorption.

Root Zone Requirements & Transpiration Stream

• Root Zone Triad: Balanced moisture, essential mineral nutrients, and dissolved oxygen.

• Transpiration Stream: Continuous water column movement driven by water potential gradients: $\text{Root} \rightarrow \text{Xylem} \rightarrow \text{Stem} \rightarrow \text{Leaves} \rightarrow \text{Atmosphere}$.

Plant Macronutrients vs. Micronutrients

• Macronutrients: Elements required in large quantities: Nitrogen ($\text{N}$), Phosphorus ($\text{P}$), Potassium ($\text{K}$), Calcium ($\text{Ca}$), Magnesium ($\text{Mg}$), and Sulfur ($\text{S}$).

• Micronutrients: Trace elements required in smaller amounts: Iron ($\text{Fe}$), Zinc ($\text{Zn}$), Manganese ($\text{Mn}$), Copper ($\text{Cu}$), Boron ($\text{B}$), and Molybdenum ($\text{Mo}$).

Hydroponic System Typology

• Deep Water Culture (DWC): Roots submerged in an aerated solution reservoir.

• Nutrient Film Technique (NFT): Recirculating shallow stream flowing over bare root mats.

• Drip System: Emitters delivering solution directly into media-supported roots.

• Ebb & Flow: Periodic flooding and complete draining of the root zone.

• Aeroponics: Suspended bare roots intermittently atomized with nutrient mist.

pH vs. Electrical Conductivity (EC)

• $\text{pH}$: Logarithmic measure of acidity/alkalinity determining chemical solubility and ionic availability to root systems.

• $\text{EC}$: Measure of electrical conductance indicating total dissolved mineral ion concentration without identifying individual nutrient ratios.

Hydroponics vs. Soil Farming Selection

• Hydroponics: Preferred when land is limited, water efficiency is paramount, urban/indoor CEA settings are used, or conditions require precise control.

• Soil Farming: Preferred when fertile arable land is available, low equipment complexity is favored, and outdoor crops are matched to regional climate.