Agricultural Plant Pest Control
What this category covers
Applicators in this category treat crops, pastures, rangeland, and other agricultural plant sites for weeds, insects, mites, diseases, nematodes, and vertebrate pests. Expect questions that force you to match a pest and a crop to a labeled site and use pattern, because a product registered on corn is not automatically legal on popcorn, sweet corn, or a cover crop grown for seed.
Concepts to master
- Thresholds. An economic threshold is the pest population at which the cost of treatment equals the value of the damage prevented; an action (treatment) threshold is the preselected trigger you actually spray at, often set slightly earlier to allow lead time.
- IPM sequence. Cultural, mechanical, biological, and genetic tactics come before, not after, a chemical decision.
- Resistance management. Rotate modes of action (IRAC/FRAC/WSSA group numbers), use labeled full rates, and never rely on one chemistry season after season.
- Label timing terms. The preharvest interval (PHI) is the minimum time between application and harvest; the restricted-entry interval (REI) governs when workers may re-enter. They are different numbers doing different jobs.
- Application mechanics. Nozzle type and spacing, carrier volume, adjuvants, and calibration determine whether the labeled rate actually lands on target.
Traps that show up in questions
Mixing up PHI and REI. Using a per-acre rate on a small plot instead of a per-1,000-square-foot rate. Assuming two products are tank-mix compatible because they are both herbicides. Forgetting that soil pH and organic matter shift the activity of soil-applied herbicides. Spraying a flowering crop while bees are foraging.
Rule of thumb with numbers
Amount of product per tank = (labeled rate per acre) x (tank size in gallons) / (sprayer output in gallons per acre). A 1.5 pt/acre rate in a 100-gallon tank at 20 GPA is 1.5 x 100/20 = 7.5 pt (120 fl oz).