Pest Identification and Pest Management
The IPM backbone
Integrated pest management means identify, monitor, set a threshold, prevent, combine tactics, and evaluate. The economic threshold is the pest density at which treatment prevents loss exceeding control cost; the economic injury level is the density where loss equals cost. Thresholds are pest-, crop-, and stage-specific, so identification comes first: a monocot vs. dicot weed, a chewing vs. piercing-sucking insect, a fungal sign vs. a nutrient-deficiency symptom. Misidentification is the most common real-world failure and a favorite exam trap.
Resistance management
Know the mode-of-action group systems (WSSA/HRAC for herbicides, IRAC for insecticides, FRAC for fungicides). Rotating trade names is not rotation - two products can share an active ingredient or a site of action. Effective rotation uses different group numbers within a season and across seasons, plus nonchemical tactics such as crop rotation, cultivation, resistant varieties, and biological control.
Traps
Treating by calendar instead of scouting; treating below threshold; assuming a neighbor's diagnosis fits your field; ignoring beneficial insects or pollinator timing; and using a herbicide that selects for resistant biotypes because it is convenient.
Worked example
A threshold is 4 larvae per sample. Your five samples read 2, 3, 8, 1, and 1. The average is 3, which is below threshold - but the 8 is a hotspot. The correct response is to re-scout and spot-treat the hotspot rather than broadcast, because averaging hides clumped distributions. Rule of thumb: sample enough locations to see the pattern, and let the threshold, not the average alone, drive the decision.