Wind speed and direction must be taken into account before you start spraying. You need to ask yourself:
- How fast is the wind blowing?
- Is the wind blowing towards or away from sensitive areas?
You can measure wind speed with a hand-held anenometer. These are available from outdoor and boating retailers from between $75 - $250. Make sure you get a model that operates well at low wind speeds.
Alternatively, use the benchmarks in the following table to assess wind speed.
|Wind speed guide
|Approx. airspeed at nozzle height
|Less than 2 km/h
||Smoke rises vertically
||Use only medium or coarse spray quality
|2 - 3 km/h
||Direction shown by smoke drift
||Avoid fine spray on warm, sunny days
|3 - 6 km/h
||Leaves rustle, wind felt on face
||Ideal spraying conditions
|6 - 10 km/h
||Leaves and twigs in constant motion
|10 - 15 km/h
||Small branches move, raises dust or loose paper
||Increased risk of spray drift, avoid fine sprays
||Small trees sway
||Extreme caution with any sprays
||Large branches sway
||Unsuitable for spraying