Preparing to use pesticides

Know the growth stage of your crop

Many pesticides only have full effect at a key stage in the life of the pest and/or crop. For example, when:

• the weed is at an early growth stage; or when
• the level of disease or the number of insects is low.

You will need to consult your pesticide label to find if there are any key stages to be aware of. If there are, you will need to estimate the dates when your crop and pest will be at that key stage and ready to spray. You will also need to read your pesticide label to find out if there is:

• a witholding period (when the treated area may not be entered), and/or
• a harvest interval during which the crop may not be harvested.

These may restrict your 'spraying window' by limiting the dates between which you can spray.

• Do not spray any plant that is in flower.
• Do not allow drift to land on any plant that is in flower.

Rain, heat, cold and wind speed can affect how well your pesticide gets to and remains on your target surfaces.

Pesticide that fails to reach the target surface, or runs off, is wasted. It not only wastes your money but it may also pollute the soil or ground or surface water.

Pesticide that drifts on the wind may contaminate you, any people or animals nearby, or other plants of value.

Assess the wind to avoid spray drift and inversions. Do not spray if the wind speed is too high or if the air is still. Often it is less windy in the early morning and in the evening.

Judge safe wind speeds by using wind socks. The ideal wind speed is 3.2 - 6.5 km/h (1.5 MB .pdf). This is a light breeze which is strong enough to feel on the face or rustle leaves. Do not spray if the wind speed is less than 3 kph: this is calm to light air where leaves are still and any smoke rises vertically. Do not spray if wind speeds are above 20 kph: this is moderate breeze where small branches and leaves move constantly in the wind.

Check your pesticide label for advice on the best weather conditions before, during and after spraying. Check the weather forecast for the best time to spray​.