ENTM 9/30 Detailed Study Notes on Insecticide Resistance and Management

Discussion on the presence of primary and secondary pests in pest management.
Quote on resistance: "With resistance, especially to insecticides, it's not really a matter of if it happens. It's a matter of when it happens."
Importance of the timing and process of chemical usage on resistance development.

Scientific Definition: Resistance refers to the heritable change in the susceptibility of a population towards an insecticide, measured through susceptibility metrics and biological definitions.
Field Level Definition: Resistance is perceived as a management failure when expected results from applications are not achieved, often influenced by human perception and situational variables.

Resistance is measured by observing differences in susceptibility and attempting to correlate field failures with scientific confirmation of resistance.
Many factors can lead to perceived failures of pest control beyond resistance, highlighting the complexity of accurate resistance assessment.

Operational Variables: The process of insecticide application can be affected by environmental conditions like rain, wind, mixing errors, and application rates.
DEFINITION of LD50 and LD90:
- $LD_{50}$ : Lethal dose at which 50% of the population is killed.
- $LD_{90}$ : Lethal dose at which 90% of the population is killed.
Shifts in these values indicate the development of resistance over time.

Inheritance and Survival: Resistant individuals survive chemical applications, reproduce, and can increase in population frequency.
Genetic Background: Resistance is often linked to genetic traits, where even low frequencies of resistance alleles can lead to significant resistance development via selection.
Population Size and Range: Larger populations and high mobility can enhance the spread of resistant alleles.
- E.g., Levodopteran moth migration affects resistance spread across regions.

Reproductive Strategies: Sexual vs. clonal reproduction affects the potential for resistance development due to genetic variability.
- Example: Aphids can reproduce clonally, leading to rapid increases in resistant populations.

Metabolic Resistance: Involves detoxification enzymes like cytochrome P450s and esterases that metabolize insecticidal compounds upon ingestion.
Target Site Insensitivity: Physiological changes at the receptor level affecting how insecticides bind to their targets.
Cuticle Modification: Changes in the insect's exoskeleton thickness and composition can lead to reduced absorption of contact insecticides.
Behavioral Resistance: Changes in insect behavior can help them evade control measures; e.g., hiding from insecticides applied to surfaces or avoiding treated areas.

Importance of Proactive Strategies: Preventing resistance development involves preemptive measures; once it develops, addressing it may be unfeasible.
Chemical Rotation: Rotating insecticides with different modes of action is critical in managing resistance and prolonging effectiveness.
IRAC Mode of Action Chart: Useful for determining effective rotation strategies among various insecticides by categorizing them into different chemical classes.

A case study illustrating effective rotation between different active ingredients based on generations of pests affecting onion crops in New York.

Concept of Refuges: Area left untreated or using different control methods can maintain susceptible populations.
High-Expression Requirement: Use of high doses of insecticides to maximize control while minimizing survival rates of resistant individuals.

Overview of various pests and their associated resistance timelines under different management strategies and conditions:
- High resistance rates were observed in low dose, low compliance scenarios across regions.
Importance of understanding selection pressure relative to insecticide application rates, host diversity, and reproduction habits.

Emphasis on the need for integrated pest management (IPM) that includes insecticide rotation, refuge strategies, and an understanding of pest biology and behavior to effectively manage resistance development over time.
Highlight the need for industry-wide collaboration and education to ensure compliance with resistance management practices and strategies.