Pest Identification, Biology, and Integrated Pest Management
What IPM actually requires
Integrated pest management combines cultural, mechanical, biological, genetic, and chemical tactics, choosing them in that general order of preference and using pesticides only when monitoring shows the pest population justifies it. Correct identification comes first - misidentification wastes money and can make the problem worse (for example, treating a disease with an insecticide).
Key concepts
- Economic threshold (action threshold) - pest density at which control should be taken to prevent the population from reaching the economic injury level.
- Economic injury level - the density that causes crop loss equal to the cost of control. The threshold sits at or below this level.
- Monitoring - scouting, sweep nets, pheromone traps, sticky cards, degree-day models, and weed counts.
- Resistance management - rotate modes of action (numbered groups), use labeled rates, avoid repeated use of one chemistry, and integrate non-chemical tactics.
Biology basics worth reviewing
Insects with complete metamorphosis (egg–larva–pupa–adult) are usually most damaging as larvae; treatment timing targets the susceptible stage. Mites are not insects (eight legs, no antennae). Plant diseases follow the disease triangle: susceptible host, virulent pathogen, favorable environment. Weeds are classified by life cycle (annual, biennial, perennial) and by monocot vs dicot; perennial weeds often require systemic herbicides and repeated treatment.
Traps
Questions love to describe a threshold scenario and ask whether to spray. Also watch for "resistance" vs "tolerance," and for biological control agents being harmed by broad-spectrum insecticides.
Worked example
Sweep samples average 3 alfalfa weevil larvae per sweep; the established threshold is 20 per sweep at the current crop height. No treatment is warranted - continue monitoring. Treating anyway costs money, selects for resistance, and kills beneficials.