Resistant

Definition

Having the capacity to withstand or survive exposure to a factor that is harmful, lethal, or inhibitory to susceptible individuals; describes genotypes, populations, or phenotypes that exhibit reduced negative response to stressors such as pesticides, pathogens, desiccation, or temperature extremes. In evolutionary and applied contexts, resistance typically involves heritable mechanisms—behavioral, physiological, biochemical, or morphological—that confer differential survival. Distinct from tolerance, which allows survival despite damage, and from immunity, which implies active recognition and response to specific antigens.

Etymology

From Latin resistere, to stand back, oppose

Example

Populations of the diamondback moth (Plutella xylostella) in agricultural regions have become resistant to pyrethroid insecticides through enhanced detoxification enzymes and target-site mutations, necessitating rotation to alternative chemistries.

Related Terms

• Tolerance
• susceptibility
• Immunity
• acclimation
• Adaptation
• insecticide resistance
• Host plant resistance

Usage Notes

In pest management, 'resistant' is often used absolutely (a population is resistant or not based on standardized bioassay thresholds), but more precisely describes a quantitative, heritable shift in dose-response curves relative to susceptible reference strains. Contrast with 'tolerant' populations that survive exposure but suffer fitness costs, and 'vigor-tolerant' individuals that withstand stress through general robustness rather than specific defensive traits. The term is sometimes loosely applied to individual survival ('this beetle is resistant'), though strictly it describes population-level or genotype-level attributes.