Application of Herbicides And Pesticides This subject is described in detail in machinery texts. However, certain basic principles related to the covering of the leaf and soil by sprays will be mentioned. The application of liquids and wettable powders by means of sprayers may be adjusted in terms of pressure and nozzle type to provide the required spray rate.

Cone nozzles produce a turbulent spray pattern suitable for fungicide and insecticide use, while fan nozzles produce a flat spray pattern for herbicide application. In periods of active plant growth, fortnightly sprays may be necessary to control pests and diseases on newly expanding foliage. High volume sprayers apply the diluted chemical at rates of 600-1000 1/ha in order to cover the whole leaf surface with droplets of 0.04-0.10 mm diameter. Cover of the underleaf surface with pesticides may be poor if nozzles are not directed horizontally or upwards.

Soil applied chemicals, e.g. herbicides or drenches, may be sprayed at a larger droplet size, 0.25-0.5 mm in diameter, through a selected fan nozzle. The correct height of the sprayer boom above the plant is essential for downward directed nozzles if the spray pattern is to be evenly distributed. Savings can be achieved …