The Rise of Insecticide Resistance

This flow traces how insect populations adapt to repeated chemical pressure and threaten the methods used against them.

increasingBearing stren­gth in each eventdecreasing

Early Signs of Resistance

A Question Asked Too Soon Older Chemicals Resistance appeared in some insects exposed to prewar inorganic sprays, though the known cases were limited. These early examples showed that chemical control could select for survival. A Warning Unheeded The possibility was familiar to specialists before synthetic pesticides became widespread. Carson argues that the rapid later growth of resistance should not have been surprising to anyone considering population variation.

The Age of Resistance

A Rapid Increase New Compounds, New Pressure The widespread use of synthetic insecticides and intensive application accelerated the appearance of resistant species. A small number of earlier cases became a growing global problem. Public Health at Risk Resistance affected insects that carried human disease as well as agricultural pests. Programs once celebrated as successful began to face the possibility that their main chemicals would stop working.

Control Methods Fail

One Chemical After Another The Housefly Example Houseflies in several regions developed resistance to DDT and then to other compounds. Replacing one chemical with another produced temporary control, not a permanent answer. A Narrowing Choice When resistance followed each new treatment, agencies faced a shrinking list of effective options. Sanitation and nonchemical methods reappeared as necessary tools rather than outdated alternatives.

Disease Vectors Adapt

A Medical Setback Mosquito Resistance Carson describes resistance in mosquito populations that carried malaria and other diseases. The list of affected vector species expanded quickly, threatening programs that depended on repeated house spraying. A Global Concern The World Health Organization identified resistance as a major technical problem. The possibility of losing effective control made the chemical strategy a public-health risk as well as an agricultural one.

The One-Way Street

Escalation Has a Limit More Is Not a Cure Greater doses and new chemicals may briefly overcome resistance, but they increase ecological and human risks. The same escalation that seeks control can accelerate the loss of effective options. A Biological Turn Carson urges energetic research into biological methods and restrained use of chemicals. The challenge is to guide natural processes rather than assume that brute force can keep pace with insect adaptation.

Before the DDT era

After 1945

Late 1940s through the 1950s

By the late 1950s

Near the end of Chapter 16