Section 5.4: Integrated Pest Management (IPM) & Resistance Management

Integrated Pest Management (IPM) & Resistance Management

Integrated Pest Management (IPM) is a science-based decision-making process that coordinates multiple pest control strategies to manage pest populations safely and economically. By relying on biological, cultural, mechanical, and chemical tools, IPM minimizes health risks, environmental damage, and financial costs. A major goal of IPM is to prevent pest resistance—the inherited ability of a pest population to survive exposure to a pesticide that was previously effective. This section details the steps of IPM, economic thresholds, non-chemical controls, resistance development, and Massachusetts school IPM laws.

The Six Steps of an IPM Program

Implementing a successful IPM program involves six structured steps:

1. Pest Identification: You must identify the target pest correctly. Understanding its biology, host plants, behavior, and life cycle is critical because control methods are highly specific. For example, applying a fungicide to control damage caused by an insect is ineffective.
2. Monitoring and Scouting: Regular field inspections (scouting) are performed to determine pest populations, beneficial insect levels, and weather conditions. Monitoring answers key questions: What pests are present? How many are there? What damage is occurring?
3. Establishing Thresholds: Pests do not need to be eliminated completely. Control actions are only taken when pest populations exceed pre-established thresholds.
4. Preventing Pest Problems: Prevention is the first line of defense. Cultural practices (such as sanitation and crop rotation) are used to keep pest populations from establishing or reaching damaging levels.
5. Implementing Controls: When thresholds are exceeded, the applicator selects a combination of biological, cultural, mechanical, and chemical control tactics. Chemical pesticides are used as a last resort, using the most selective and lowest-risk products available.
6. Evaluating Results: Keep records of monitoring data, actions taken, and the results of the control measures. This documentation helps improve the IPM plan for subsequent seasons.

Economic Threshold vs. Economic Injury Level

In agricultural and commercial IPM, control decisions are based on two critical levels:

• Economic Injury Level (EIL): The pest population density at which the cost of pest control equals the economic loss caused by the pest's damage. If the pest population rises above the EIL, the applicator suffers a financial loss because the crop damage exceeds the treatment cost.
• Economic Threshold (ET) or Action Threshold: The pest population density at which control measures should be initiated to prevent the population from reaching the Economic Injury Level. The ET is always set lower than the EIL to allow time for the control measures to take effect before the pest population inflicts economic damage.

Pest Density
  ^
  |      /\  <-- Pest population growth
  |-----/--\---------------------------- Economic Injury Level (EIL)
  |    /    \     (Pest damage cost = treatment cost)
  |---/------\-------------------------- Economic Threshold (ET / Action Threshold)
  |  /        \   (Apply controls here!)
  | /          \
--+------------------------------------> Time

Non-Chemical Control Tactics

IPM programs prioritize non-chemical tactics to suppress pest populations:

Biological Control

Biological control utilizes natural enemies to suppress pest populations. This includes predators (e.g., lady beetles or green lacewings eating aphids), parasitoids (e.g., tiny wasps that lay eggs inside pest caterpillars), and pathogens (e.g., Bacillus thuringiensis or Bt, a soil bacterium that produces proteins toxic to specific insect larvae). Protecting native beneficial insects is a key part of biological control.

Cultural Control

Cultural controls disrupt the pest's environment to prevent establishment. Examples include:

• Sanitation: Removing crop residues, fallen leaves, or weeds that harbor overwintering pests.
• Crop Rotation: Changing the crop species grown in a field annually to break the life cycles of host-specific pests.
• Resistant Cultivars: Planting crop varieties that have genetic resistance to specific insects or diseases.
• Soil Management: Aeration, proper fertilization, and irrigation to keep plants healthy, making them more resilient to pests.

Mechanical and Physical Control

Mechanical controls physically block, trap, or kill pests. Examples include:

• Barriers: Installing row covers, tree wraps, or screens to exclude insects.
• Traps: Using sticky cards or pheromone traps to capture insects.
• Tillage: Plowing soil to destroy weeds and expose soil-dwelling pupae to predators and freezing temperatures.
• Hand-pulling: Manually removing weeds from small areas.

Pest Resistance Management

Pesticides exert a strong selective pressure on pest populations. Within any pest population, natural genetic variation exists. A tiny fraction of the population may possess genes that allow them to survive exposure to a pesticide. When the same pesticide (or pesticides with the same mode of action) is applied repeatedly:

1. Susceptible pests are killed.
2. The few resistant individuals survive, reproduce, and pass their resistant genes to their offspring.
3. Over time, the resistant individuals become the majority of the population, rendering the pesticide ineffective.

Resistance Management Strategies

• Rotate Modes of Action (MOA): Pesticides are classified by their mode of action using codes on the product label: HRAC (herbicides), IRAC (insecticides), and FRAC (fungicides). Applicators must rotate between products with different group numbers. Never use products with the same group number in succession.
• Tank-mix Products: Combine two pesticides with different modes of action, provided it is allowed by the label and they are chemically compatible.
• Integrate Non-Chemical Controls: Rely heavily on cultural, mechanical, and biological tactics to reduce pesticide use and lower the selective pressure.
• Apply at Labeled Rates: Always use the full recommended rate. Under-applying allows moderately resistant pests to survive and pass on their genes, accelerating resistance development.

Massachusetts School IPM Laws (333 CMR 14.00)

Under Massachusetts law (333 CMR 14.00), all public and private schools, daycare facilities, and school-age child care programs must practice IPM. The law mandates:

• Written IPM Plans: Facilities must develop and maintain a written, site-specific IPM plan that is updated annually and filed with the Massachusetts Department of Agricultural Resources (MDAR).
• Notification Requirements: Standard pesticides (non-low-impact) cannot be applied unless a written notice is sent to parents, guardians, and staff at least two working days prior to application. Low-impact pesticides (such as gel baits and antimicrobial products) are exempt from this notification requirement.
• Outdoor Application Restrictions: Standard pesticides may not be applied to school turf, playgrounds, or athletic fields unless an emergency waiver is granted by the local board of health or MDAR to address a public health threat (such as stinging insect nests or disease-vector mosquitoes).