Chapter 6: Spray drift

Question 1

What is drift?

Answer 1

1. The downwind movement of spray droplets by the wind at the time of a spray application to areas, which are outside treated fields, can cause unacceptable effects depending on the type of plant protection product
2. Downwind drift of vapor may also occur after a spray application from foliar deposits due to the volatility of the plant protection product, if temperatures are sufficiently high
3. Vapor drift can occur more than 12 hours after application

Question 2

What kind of drifts?

Answer 2

Exo-drift: movement of spray droplets beyond the edge of a treated field

Endo-drift: distribution of a plant protection product within a field, but not on the intended target

Question 3

How can drift be measured?

Answer 3

• An international standard for measurement of drift (ISO 22866) is designed to cover both:

1. Short range down wind sedimentation of spray
2. Longer range airborne drift of the smaller spray droplets

• Most assessments are made with a tracer dye quantified by spectro-fluorometric analysis

Question 4

What are the factors influencing the drift?

Answer 4

1. Meteorological conditions (wind speed, wind direction, temperature, humidity)
2. Droplet sizes
3. Time of drop evaporation
4. PPP mixture (formulated product + water + adjuvant)
5. Type of sprayer and height of boom
6. Type of nozzles and pressure
7. Speed of tractor movement
8. Vegetative period

Question 5

How can drift be minimized?

Answer 5

1. Avoid spraying when the wind blows toward sensitive areas
2. Carefully chose a plant protection product
3. Avoid highly volatile chemicals
4. Select nozzles that produce larger droplets
5. Lower the spray pressure
6. Lower the spray boom
7. Respect buffer zones required to protect sensitive areas such as housing, schools, hospitals or water bodies

Question 6

How PPPs enter the water? Roots of contamination?

Answer 6

1. Drift
2. Run-off
3. Leaching