Growsafe Pesticide Application Methods 1 — Questions and Answers
Question 1: What is the most common method of applying liquid agrichemicals to crops in New Zealand?
- Boom spraying (Correct answer)
- Granule broadcasting
- Fumigation
- Thermal fogging
Correct answer: Boom spraying
Boom spraying is the most common method for applying liquid agrichemicals to broadacre crops in New Zealand, using a horizontal boom fitted with nozzles to apply product uniformly across a wide area.
Question 2: What factor most significantly affects spray droplet size in a boom sprayer?
- Nozzle type and operating pressure (Correct answer)
- The colour of the spray solution
- The temperature of the water used
- The time of day of application
Correct answer: Nozzle type and operating pressure
Nozzle type and operating pressure are the primary determinants of spray droplet size. Different nozzles produce different droplet spectra, and pressure changes within a nozzle type also affect droplet size.
Question 3: Why is spray droplet size important when applying agrichemicals?
- Smaller droplets increase drift risk while larger droplets improve coverage of target surfaces in some applications (Correct answer)
- Droplet size only affects how quickly the tank empties
- Larger droplets always provide better results regardless of the application
- Droplet size is irrelevant as long as the correct rate per hectare is achieved
Correct answer: Smaller droplets increase drift risk while larger droplets improve coverage of target surfaces in some applications
Droplet size affects both coverage and drift. Fine droplets can drift off-target but provide good coverage on complex surfaces, while coarser droplets reduce drift but may not provide as thorough coverage. The optimal size depends on the product and target.
Question 4: What is 'calibration' of a spray boom and why is it important?
- The process of confirming that the sprayer delivers the correct volume of product per hectare as specified on the label (Correct answer)
- A method of adjusting the pH of the spray solution before application
- A test to confirm that nozzles are not blocked
- A process of checking that the boom height is set correctly for the crop being sprayed
Correct answer: The process of confirming that the sprayer delivers the correct volume of product per hectare as specified on the label
Calibration ensures the sprayer applies the correct product rate. Under-application may fail to control the target pest, while over-application wastes product, increases costs, and may leave excessive residues.
Question 5: What is the purpose of using a 'flat fan' nozzle in broadacre spraying?
- To produce a flat, fan-shaped spray pattern that provides uniform coverage across the boom width (Correct answer)
- To generate large droplets that fall quickly to prevent drift
- To apply product in a circular pattern around individual plants
- To apply product in an ultra-fine mist for fumigation purposes
Correct answer: To produce a flat, fan-shaped spray pattern that provides uniform coverage across the boom width
Flat fan nozzles produce a flat, fan-shaped spray pattern that overlaps with adjacent nozzles on the boom to create uniform coverage. They are the most common nozzle type in broadacre spraying.
Question 6: Under what wind conditions should aerial or boom spraying generally be avoided?
- When wind speed exceeds the product label limit, typically above 15-20 km/h for many products (Correct answer)
- Only when there is no wind at all
- Only when the wind is blowing directly toward the operator
- When wind speed exceeds 40 km/h for any product
Correct answer: When wind speed exceeds the product label limit, typically above 15-20 km/h for many products
High wind speeds increase the risk of spray drift onto non-target areas, including neighbouring properties, waterways, and sensitive crops. Label instructions specify maximum wind speed conditions for application.
