Ecological & Integrated Pest Management

Ecological & Integrated Pest Management Study Notes

Lecture Details

• Speaker: Tara Pisani Gareau

• Course: EESC3310 Agroecology

• Date: March 17, 2026

Learning Objectives

• To describe main strategies of Integrated Pest Management (IPM)

• To understand the conditions that give rise to weed, insect, and disease pressure in an agroecosystem

• To describe Ecological Pest Management (EPM) for weeds, insects, and pathogens

• To apply ecological principles such as disturbance, tolerance, competition, allelopathy, and herbivory to EPM

Defining Pests

• Insect Pests:

  • Defined as insects that reduce the yield and/or market quality of crops.

  • Can act as vectors for disease transmission.

  • Statistics: Only 1-3% of insect species are classified as pests.

• Weeds:

  • Plants that compete with crops for essential resources: nutrients, water, sunlight, and space.

• Microorganism Pests:

  • Include bacteria, viruses, fungi, and protozoa that act as pathogens, causing diseases in crops and animals.

Pesticides: A Conventional Control Tactic

• Pesticide Usage Trends:

  • A chart illustrating the usage of pesticides over the years shows the total million pounds of pesticide active ingredients, categorized into herbicides, insecticides, and fungicides, from 1960 to the early 2000s.

• Historical Data:

  • In 1968, the ten most heavily used pesticides included five insecticides and five herbicides.

  • By 2008, the most used pesticides were predominantly herbicides, showcasing a shift in pest management practices.

Biopesticides

• Definition:

  • Biopesticides are chemicals derived from natural materials. Examples include:

  • Neem oil

  • Various essential oils (peppermint, cedar, rosemary, etc.)

  • Sulfur

  • Copper sulfate

  • Potassium bicarbonate

• Microbial Pesticides:

  • Include microorganisms that control pest populations, such as:

  • Bacillus thuringiensis (Bt)

  • Trichoderma asperellum (a filamentous fungi)

• Advantages of Biopesticides:

  • Targeted action

  • Rapid breakdown in the environment

  • Lower toxicity compared to conventional pesticides

Integrated Pest Management (IPM)

• Overview:

  • A comprehensive approach integrating strategies to reduce pest establishment and guide informed decision-making regarding interventions and controls.

• Key Components of IPM:

  1. Prevention: Initiatives to deter pests before they become problematic.

  2. Pest Identification: Correctly identifying pest species to tailor management strategies effectively.

  3. Monitoring: Regular observation and data collection to track pest populations.

  4. Using Economic Thresholds: Understanding the level of pest presence that necessitates control actions.

  5. Control Measures: Implementing specific interventions when necessary.

  6. Evaluation of Measures: Assessing the effectiveness of control methods applied.

Goals of IPM

• To diminish the pest population to a tolerable level.

• The definition of tolerable is influenced by the Economic Injury Level (EIL), which represents the insect density that will incur economic damage.

• To safeguard environmental resources and processes.

Prevention Strategies in IPM

• Cultural Practices:

  • Selecting disease-resistant and insect-resistant plant varieties.

  • Appropriate plant spacing and design to minimize competition.

  • Adjusting planting dates to avoid synchrony with pest life cycles.

  • Implementing crop rotations to disrupt pest cycles.

  • Practicing intercropping to reduce visibility of crops to pests.

  • Early mowing of weeds to prevent seed dispersal.

  • Utilizing targeted irrigation (e.g., drip irrigation) to direct water to crops.

  • Techniques such as mating disruption to hinder pest reproduction.

Monitoring Pest Populations

• Establishing a standardized number of samples to compare the pest population across sampling dates.

• Recognizing that early detection of pest problems is crucial for effective management.

Economic Injury Levels (EIL)

• Definition:

  • The Economic Injury Level is defined as the lowest population density of a pest that will lead to economic damage, essentially dictating when the cost of pest control measures will be justified.

Applying Action Thresholds

• Action Threshold:

  • Specifies the pest density at which control measures should be enacted. For instance, the Threshold for Blackheaded Fireworm (Rhopobota naevana (Hübner)), noted as 1-2 larvae per 25 sweeps.

Control Measures in IPM

• Types of Control Options:

  • Chemical Control:

  • Conventional pesticides that eliminate pests on contact.

  • Use of biorational products, repellents, diatomaceous earth, and oils.

  • Biological Control:

  • Involves the use of natural predators or parasitoids to control pest populations.

  • Physical or Mechanical Controls:

  • Using tools like flea/lice combs, screens, or proper clothing as barriers against pests.

  • Cultural Controls:

  • From good sanitation to habitat modifications for pest deterrence.

Biological Control Techniques

• Types of Biological Control:

  1. Classical Biological Control:

  • Involves releasing an exotic natural enemy to manage an exotic pest, requiring a regional effort.

  1. Augmentative Biological Control:

  • Increasing the resident populations of natural enemies at the farm level.

  1. Conservation:

  • Creating favorable habitats and minimizing mortality factors for resident populations of natural enemies across farm to landscape levels.

Habitat Needs of Natural Enemies

• Essential components include:

  • Bountiful sources of pollen and nectar for energy and reproduction.

  • Presence of primary and alternative prey for parasitoids to feed upon and reproduce.

  • Favorable microclimate conditions and protective environments.

Examples of Insect Predators

• Green lacewing

• Lady beetle

• Big-eyed bugs

• Minute pirate bugs

• Damsel bugs

• Assassin bugs

• Syrphid flies

Monitoring for Parasitoids

• Examples include:

  • Ichneumonid wasp

  • Apanteles militaris

  • Braconid wasp

Ecological Weed Management

• Philosophy:

  • Multiple and temporally variable stresses can be imposed on weeds to result in acceptable crop yield and quality (Liebman and Gallandt 1997: 327).

Goals of Ecological Weed Management

1. To reduce the density of weed propagules and seedlings.

2. To decrease the rate of weed seedling emergence.

3. To give the crop a competitive advantage over weeds.

4. To mitigate the rate of weed seed dispersal both within and between fields.

5. To lower the proportion of noxious weeds in the weed community.

Strategies to Reduce Weed Propagules & Seedlings

1. Cultivation:

   • Mechanically disturbing and eliminating weeds to prevent proliferation.

2. Mulch/Cover Crops:

   • Using hay, straw, plastic, and paper to suppress weeds by blocking light and retaining moisture.

3. Allelopathy:

   • Utilizing plants that release chemicals to suppress weed growth (example: glucosinolates from broccoli and mustard).

4. Crop Rotation:

   • Regularly changing the types of crops grown to disrupt weed growth cycles.

5. Biological Control:

   • Using natural enemies of weeds as a form of management.

6. Solarization:

   • Irrigating and covering ground with clear polyethylene film to kill weeds through heat.

Case Study: IPM for Maize in Kenya

• Pest Details:

  • Focus on stalk borers: Chilo partellus (found in warmer lowlands) and Busseola fusca (found in cooler highlands).

  • Yield Loss: Documented losses range from 34-43% as per Alghali 1992.

  • Economic Injury Level (EIL) calculated as 3.2-3.9 larvae per plant.

Managing Witchweed

• Striga hermonthica:

  • A parasitic plant that entwines its roots with maize roots, extracting sugars, nutrients, and water.

  • Microscopic representation shows its invasive method and impact on host crops.

Push-Pull Technology in Kenya

• A method utilizing Desmodium roots that stimulate germination of Striga seeds while simultaneously inhibiting Striga attachment to maize roots.

• Result: This allelopathic effect has demonstrated a 3-6 times increase in corn yield and enhanced forage availability for livestock.

Ecological Disease Management

• Common Plant Pathogens:

  • Apple Scab (Venturia inaequalis)

  • Late Blight (Phytophthora infestans)

  • Powdery Mildew (Erysiphe spp.)

  • Represent various modes of attack on host plants, leading to decay or wilting.

Disease Triangle

• Components:

  1. Host: A susceptible variety that is not fully resistant to the disease.

  2. Pathogen: The bacterium, fungus, or virus that induces disease.

  3. Environment: Conditions that promote disease proliferation (e.g., frequent rain, high humidity, moderate temperatures).

Ecological Disease Management Strategies

• Host Strategies:

  • Use resistant crop varieties and maintain good sanitation practices.

• Environmental Strategies:

  • Implement crop rotations and adequate crop spacing for better air circulation.

  • Use mulches to prevent soil splash onto foliage.

• Pathogen Control:

  • Minimizing insect vectors that transport pathogens (e.g., aphids and leafhoppers) and applying antibacterial or antifungal treatments.

Lifecycle of Bacterial Wilt

• Pathogen: Ralstonia solanacearum.

• Favorable conditions for the pathogen include:

  • High soil temperatures (above 85 °F)

  • Elevated soil moisture content.

EDM of Bacterial Wilt

• Host Strategies:

  • Selecting resistant tomato varieties (e.g., ‘Venus’, ‘Saturn’) and potato varieties (e.g., ‘Red Pearl’).

  • Start crops with clean, uncontaminated seeds and tubers.

• Environmental Strategies:

  • Rotate crops with non-host plants.

  • Employ clean equipment to prevent pathogen spread.

• Pathogen Management:

  • Soil solarization of infected areas and potential biocontrol with brassica crop residues as biofumigation.

  • Use of microbial biocides where necessary.