Field Crop: Drift, Timing, and Resistance Management
What the exam tests
Field crop pest management emphasizes correct product selection, application timing based on pest thresholds, drift and runoff prevention, and resistance management. Expect scenarios involving weeds, insects, and diseases across corn, soybean, and small grains.
Concepts to master
- Economic threshold and scouting. Treat when pest pressure justifies cost; scout rather than spray on a calendar. Know concepts like weed emergence timing and insect growth stages that determine the vulnerable window.
- Drift management. Droplet size, nozzle selection, boom height, wind speed, and inversions all affect off-target movement. Small droplets and temperature inversions are major drift risks. Follow label buffers and wind restrictions.
- Herbicide resistance. Rotate sites of action (SOA groups), use multiple effective modes, and integrate cultural practices. Repeated use of one SOA selects resistant weeds.
- Runoff and leaching. Soil type, slope, and timing relative to rainfall matter; avoid application before heavy rain.
- Application calibration. Correct GPA, nozzle spacing, and speed ensure the labeled rate is delivered uniformly.
Traps
Questions pair a "best" answer with a tempting shortcut-like spraying during a calm, clear evening that is actually an inversion (drift risk). Another trap: treating at the labeled maximum rate every time instead of rotating modes of action. Also watch for confusing PHI with the crop growth stage.
Rule of thumb
Right product, right rate, right time, right place. For resistance, never rely on one SOA in consecutive seasons. Worked example: A 200-gallon tank at 20 GPA covers 10 acres (200 ÷ 20 = 10). If the label calls for 1.5 pt/acre, add 15 pt total to the tank.