Calibrate for best pest control

How you calibrate your knapsack sprayer depends on your pesticide label and how it states the pesticide dose. The dose may be given as a:

• A pesticide dose rate for a measured area.
• A pesticide dose as a concentration in water.

A pesticide dose rate for a measured area

Pesticide labels often advise a pesticide dose rate for a measured area (e.g. 4 kg/ha) with a spray mix or water volume rate (e.g. 400 L/ha). Labels may also state which type of nozzle to use at which pressure and name the drop size. For example:

A pesticide dose rate as a concerntration water

A pesticide dose as a concentration in water might be shown as:

• 2% of pesticide in water
• 50 ml or 50 g of pesticide in 100 L of water
• 4 L or 4 Kg of pesticide in 100 L of water.

Or the dose may be stated as an amount of pesticide for:

• one plant (e.g. 10 ml/plant)
• a number of plants (e.g. 10 ml/100 plants)
• a length of row (e.g. 100 ml/100 metres).

These can be converted into a concentration.

Some labels may also give a spray mix volume rate as a maximum amount to apply to an area e.g. "Do not apply more than 1,000 L/ha". In this case, note any advice given on the type of spray drop cover that you need to get. Then calibrate for a spray concentration in water. 

Some labels may state a spray mix/water volume rate for a measured area, e.g. apply a pesticide dose concentration of 50 g in 100 L of water, using 1000 L of water per hectare. In this case convert the concentration into a dose rate for a measured area using this formula: 

[Spray mix volume rate (L/ha) / litres of water stated in dose] x amount of pesticide stated in dose (L, ml, kg, g) } e.g. 50 g in 100 L of water, apply at 300 L/ha. The pesticide dose rate is { [ 300/100 ] x 50 } = 150 g/ha 

Then calibrate your sprayer as for a pesticide dose for a measured area.