Pest Identification and Integrated Pest Management
The IPM process
IPM is a decision framework, not a ban on pesticides: identify the pest correctly, monitor and scout, compare the population to a threshold, choose the least-risk effective combination of tactics, then evaluate results. The economic injury level (EIL) is the pest density at which damage equals the cost of control; the action threshold is set at or below the EIL to allow lead time. Treating on a calendar schedule without scouting is the classic anti-IPM answer on exams.
Tactics
- Cultural: resistant varieties, sanitation, crop rotation, planting date, fertility and irrigation management.
- Mechanical/physical: cultivation, mulching, exclusion, traps, hand removal.
- Biological: predators, parasitoids, pathogens, conservation of natural enemies.
- Chemical: the last tier, chosen for target specificity and lowest risk.
Plant disease is best understood with the disease triangle: susceptible host + virulent pathogen + favorable environment. Remove any one leg and disease does not occur. Weed management hinges on identifying the weed and its life cycle (annual, biennial, perennial) and preventing seed set and seed-bank buildup.
Resistance management
The single most tested concept: rotate mode-of-action groups, using the IRAC (insecticide), FRAC (fungicide), and HRAC (herbicide) group numbers on the label - not brand names. Two different pyrethroid products are both IRAC Group 3, so alternating them does nothing to delay resistance. Use labeled rates (never sub-lethal), tank-mix or sequence different groups, and use nonchemical tactics in the rotation. Distinguish resistance (heritable, survives a labeled rate) from resurgence (natural enemies killed) and secondary pest outbreak (a nontarget species fills the gap).
Rule of thumb: treat only when the pest is positively identified, at or above threshold, and nonchemical options have been used or are inadequate.