Resistance to a pesticide that the pest has not previously been exposed to but that has a mode of action similar to the pesticide that selected for resistance is called what?

• A. Cross-resistance
• B. Cultural Control
• C. Curative
• D. Directed application

Answer: (A)

Cross-resistance occurs when a pest that has developed resistance to one pesticide also shows resistance to another pesticide with a similar mode of action, even though it hasn’t been exposed to that second chemical. The underlying resistance mechanism—such as enhanced detoxification or a changed target site—affects multiple pesticides that work in the same way, so the second pesticide is less effective as well. For example, if a pest becomes resistant to an insecticide that inhibits a specific enzyme, it may also resist another insecticide that targets the same enzyme because the pest’s defense mechanism blocks both. This concept is different from cultural control (nonchemical methods), curative treatment (killing pests after infestation), or directed application (applying pesticide to where pests are present), which describe management tactics rather than resistance patterns.